+++ /dev/null
-How fio works
--------------
-
-The first step in getting fio to simulate a desired I/O workload, is writing a
-job file describing that specific setup. A job file may contain any number of
-threads and/or files -- the typical contents of the job file is a *global*
-section defining shared parameters, and one or more job sections describing the
-jobs involved. When run, fio parses this file and sets everything up as
-described. If we break down a job from top to bottom, it contains the following
-basic parameters:
-
-`I/O type`_
-
- Defines the I/O pattern issued to the file(s). We may only be reading
- sequentially from this file(s), or we may be writing randomly. Or even
- mixing reads and writes, sequentially or randomly.
- Should we be doing buffered I/O, or direct/raw I/O?
-
-`Block size`_
-
- In how large chunks are we issuing I/O? This may be a single value,
- or it may describe a range of block sizes.
-
-`I/O size`_
-
- How much data are we going to be reading/writing.
-
-`I/O engine`_
-
- How do we issue I/O? We could be memory mapping the file, we could be
- using regular read/write, we could be using splice, async I/O, or even
- SG (SCSI generic sg).
-
-`I/O depth`_
-
- If the I/O engine is async, how large a queuing depth do we want to
- maintain?
-
-
-`Target file/device`_
-
- How many files are we spreading the workload over.
-
-`Threads, processes and job synchronization`_
-
- How many threads or processes should we spread this workload over.
-
-The above are the basic parameters defined for a workload, in addition there's a
-multitude of parameters that modify other aspects of how this job behaves.
-
-
-Command line options
---------------------
-
-.. option:: --debug=type
-
- Enable verbose tracing `type` of various fio actions. May be ``all`` for all types
- or individual types separated by a comma (e.g. ``--debug=file,mem`` will
- enable file and memory debugging). Currently, additional logging is
- available for:
-
- *process*
- Dump info related to processes.
- *file*
- Dump info related to file actions.
- *io*
- Dump info related to I/O queuing.
- *mem*
- Dump info related to memory allocations.
- *blktrace*
- Dump info related to blktrace setup.
- *verify*
- Dump info related to I/O verification.
- *all*
- Enable all debug options.
- *random*
- Dump info related to random offset generation.
- *parse*
- Dump info related to option matching and parsing.
- *diskutil*
- Dump info related to disk utilization updates.
- *job:x*
- Dump info only related to job number x.
- *mutex*
- Dump info only related to mutex up/down ops.
- *profile*
- Dump info related to profile extensions.
- *time*
- Dump info related to internal time keeping.
- *net*
- Dump info related to networking connections.
- *rate*
- Dump info related to I/O rate switching.
- *compress*
- Dump info related to log compress/decompress.
- *steadystate*
- Dump info related to steadystate detection.
- *helperthread*
- Dump info related to the helper thread.
- *zbd*
- Dump info related to support for zoned block devices.
- *?* or *help*
- Show available debug options.
-
-.. option:: --parse-only
-
- Parse options only, don't start any I/O.
-
-.. option:: --merge-blktrace-only
-
- Merge blktraces only, don't start any I/O.
-
-.. option:: --output=filename
-
- Write output to file `filename`.
-
-.. option:: --output-format=format
-
- Set the reporting `format` to `normal`, `terse`, `json`, or `json+`. Multiple
- formats can be selected, separated by a comma. `terse` is a CSV based
- format. `json+` is like `json`, except it adds a full dump of the latency
- buckets.
-
-.. option:: --bandwidth-log
-
- Generate aggregate bandwidth logs.
-
-.. option:: --minimal
-
- Print statistics in a terse, semicolon-delimited format.
-
-.. option:: --append-terse
-
- Print statistics in selected mode AND terse, semicolon-delimited format.
- **Deprecated**, use :option:`--output-format` instead to select multiple
- formats.
-
-.. option:: --terse-version=version
-
- Set terse `version` output format (default 3, or 2 or 4 or 5).
-
-.. option:: --version
-
- Print version information and exit.
-
-.. option:: --help
-
- Print a summary of the command line options and exit.
-
-.. option:: --cpuclock-test
-
- Perform test and validation of internal CPU clock.
-
-.. option:: --crctest=[test]
-
- Test the speed of the built-in checksumming functions. If no argument is
- given, all of them are tested. Alternatively, a comma separated list can
- be passed, in which case the given ones are tested.
-
-.. option:: --cmdhelp=command
-
- Print help information for `command`. May be ``all`` for all commands.
-
-.. option:: --enghelp=[ioengine[,command]]
-
- List all commands defined by `ioengine`, or print help for `command`
- defined by `ioengine`. If no `ioengine` is given, list all
- available ioengines.
-
-.. option:: --showcmd=jobfile
-
- Convert `jobfile` to a set of command-line options.
-
-.. option:: --readonly
-
- Turn on safety read-only checks, preventing writes and trims. The
- ``--readonly`` option is an extra safety guard to prevent users from
- accidentally starting a write or trim workload when that is not desired.
- Fio will only modify the device under test if
- `rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite` is given. This
- safety net can be used as an extra precaution.
-
-.. option:: --eta=when
-
- Specifies when real-time ETA estimate should be printed. `when` may be
- `always`, `never` or `auto`. `auto` is the default, it prints ETA
- when requested if the output is a TTY. `always` disregards the output
- type, and prints ETA when requested. `never` never prints ETA.
-
-.. option:: --eta-interval=time
-
- By default, fio requests client ETA status roughly every second. With
- this option, the interval is configurable. Fio imposes a minimum
- allowed time to avoid flooding the console, less than 250 msec is
- not supported.
-
-.. option:: --eta-newline=time
-
- Force a new line for every `time` period passed. When the unit is omitted,
- the value is interpreted in seconds.
-
-.. option:: --status-interval=time
-
- Force a full status dump of cumulative (from job start) values at `time`
- intervals. This option does *not* provide per-period measurements. So
- values such as bandwidth are running averages. When the time unit is omitted,
- `time` is interpreted in seconds. Note that using this option with
- ``--output-format=json`` will yield output that technically isn't valid
- json, since the output will be collated sets of valid json. It will need
- to be split into valid sets of json after the run.
-
-.. option:: --section=name
-
- Only run specified section `name` in job file. Multiple sections can be specified.
- The ``--section`` option allows one to combine related jobs into one file.
- E.g. one job file could define light, moderate, and heavy sections. Tell
- fio to run only the "heavy" section by giving ``--section=heavy``
- command line option. One can also specify the "write" operations in one
- section and "verify" operation in another section. The ``--section`` option
- only applies to job sections. The reserved *global* section is always
- parsed and used.
-
-.. option:: --alloc-size=kb
-
- Allocate additional internal smalloc pools of size `kb` in KiB. The
- ``--alloc-size`` option increases shared memory set aside for use by fio.
- If running large jobs with randommap enabled, fio can run out of memory.
- Smalloc is an internal allocator for shared structures from a fixed size
- memory pool and can grow to 16 pools. The pool size defaults to 16MiB.
-
- NOTE: While running :file:`.fio_smalloc.*` backing store files are visible
- in :file:`/tmp`.
-
-.. option:: --warnings-fatal
-
- All fio parser warnings are fatal, causing fio to exit with an
- error.
-
-.. option:: --max-jobs=nr
-
- Set the maximum number of threads/processes to support to `nr`.
- NOTE: On Linux, it may be necessary to increase the shared-memory
- limit (:file:`/proc/sys/kernel/shmmax`) if fio runs into errors while
- creating jobs.
-
-.. option:: --server=args
-
- Start a backend server, with `args` specifying what to listen to.
- See `Client/Server`_ section.
-
-.. option:: --daemonize=pidfile
-
- Background a fio server, writing the pid to the given `pidfile` file.
-
-.. option:: --client=hostname
-
- Instead of running the jobs locally, send and run them on the given `hostname`
- or set of `hostname`\s. See `Client/Server`_ section.
-
-.. option:: --remote-config=file
-
- Tell fio server to load this local `file`.
-
-.. option:: --idle-prof=option
-
- Report CPU idleness. `option` is one of the following:
-
- **calibrate**
- Run unit work calibration only and exit.
-
- **system**
- Show aggregate system idleness and unit work.
-
- **percpu**
- As **system** but also show per CPU idleness.
-
-.. option:: --inflate-log=log
-
- Inflate and output compressed `log`.
-
-.. option:: --trigger-file=file
-
- Execute trigger command when `file` exists.
-
-.. option:: --trigger-timeout=time
-
- Execute trigger at this `time`.
-
-.. option:: --trigger=command
-
- Set this `command` as local trigger.
-
-.. option:: --trigger-remote=command
-
- Set this `command` as remote trigger.
-
-.. option:: --aux-path=path
-
- Use the directory specified by `path` for generated state files instead
- of the current working directory.
-
-Any parameters following the options will be assumed to be job files, unless
-they match a job file parameter. Multiple job files can be listed and each job
-file will be regarded as a separate group. Fio will :option:`stonewall`
-execution between each group.
-
-
-Job file format
----------------
-
-As previously described, fio accepts one or more job files describing what it is
-supposed to do. The job file format is the classic ini file, where the names
-enclosed in [] brackets define the job name. You are free to use any ASCII name
-you want, except *global* which has special meaning. Following the job name is
-a sequence of zero or more parameters, one per line, that define the behavior of
-the job. If the first character in a line is a ';' or a '#', the entire line is
-discarded as a comment.
-
-A *global* section sets defaults for the jobs described in that file. A job may
-override a *global* section parameter, and a job file may even have several
-*global* sections if so desired. A job is only affected by a *global* section
-residing above it.
-
-The :option:`--cmdhelp` option also lists all options. If used with a `command`
-argument, :option:`--cmdhelp` will detail the given `command`.
-
-See the `examples/` directory for inspiration on how to write job files. Note
-the copyright and license requirements currently apply to `examples/` files.
-
-So let's look at a really simple job file that defines two processes, each
-randomly reading from a 128MiB file:
-
-.. code-block:: ini
-
- ; -- start job file --
- [global]
- rw=randread
- size=128m
-
- [job1]
-
- [job2]
-
- ; -- end job file --
-
-As you can see, the job file sections themselves are empty as all the described
-parameters are shared. As no :option:`filename` option is given, fio makes up a
-`filename` for each of the jobs as it sees fit. On the command line, this job
-would look as follows::
-
-$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
-
-
-Let's look at an example that has a number of processes writing randomly to
-files:
-
-.. code-block:: ini
-
- ; -- start job file --
- [random-writers]
- ioengine=libaio
- iodepth=4
- rw=randwrite
- bs=32k
- direct=0
- size=64m
- numjobs=4
- ; -- end job file --
-
-Here we have no *global* section, as we only have one job defined anyway. We
-want to use async I/O here, with a depth of 4 for each file. We also increased
-the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical
-jobs. The result is 4 processes each randomly writing to their own 64MiB
-file. Instead of using the above job file, you could have given the parameters
-on the command line. For this case, you would specify::
-
-$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
-
-When fio is utilized as a basis of any reasonably large test suite, it might be
-desirable to share a set of standardized settings across multiple job files.
-Instead of copy/pasting such settings, any section may pull in an external
-:file:`filename.fio` file with *include filename* directive, as in the following
-example::
-
- ; -- start job file including.fio --
- [global]
- filename=/tmp/test
- filesize=1m
- include glob-include.fio
-
- [test]
- rw=randread
- bs=4k
- time_based=1
- runtime=10
- include test-include.fio
- ; -- end job file including.fio --
-
-.. code-block:: ini
-
- ; -- start job file glob-include.fio --
- thread=1
- group_reporting=1
- ; -- end job file glob-include.fio --
-
-.. code-block:: ini
-
- ; -- start job file test-include.fio --
- ioengine=libaio
- iodepth=4
- ; -- end job file test-include.fio --
-
-Settings pulled into a section apply to that section only (except *global*
-section). Include directives may be nested in that any included file may contain
-further include directive(s). Include files may not contain [] sections.
-
-
-Environment variables
-~~~~~~~~~~~~~~~~~~~~~
-
-Fio also supports environment variable expansion in job files. Any sub-string of
-the form ``${VARNAME}`` as part of an option value (in other words, on the right
-of the '='), will be expanded to the value of the environment variable called
-`VARNAME`. If no such environment variable is defined, or `VARNAME` is the
-empty string, the empty string will be substituted.
-
-As an example, let's look at a sample fio invocation and job file::
-
-$ SIZE=64m NUMJOBS=4 fio jobfile.fio
-
-.. code-block:: ini
-
- ; -- start job file --
- [random-writers]
- rw=randwrite
- size=${SIZE}
- numjobs=${NUMJOBS}
- ; -- end job file --
-
-This will expand to the following equivalent job file at runtime:
-
-.. code-block:: ini
-
- ; -- start job file --
- [random-writers]
- rw=randwrite
- size=64m
- numjobs=4
- ; -- end job file --
-
-Fio ships with a few example job files, you can also look there for inspiration.
-
-Reserved keywords
-~~~~~~~~~~~~~~~~~
-
-Additionally, fio has a set of reserved keywords that will be replaced
-internally with the appropriate value. Those keywords are:
-
-**$pagesize**
-
- The architecture page size of the running system.
-
-**$mb_memory**
-
- Megabytes of total memory in the system.
-
-**$ncpus**
-
- Number of online available CPUs.
-
-These can be used on the command line or in the job file, and will be
-automatically substituted with the current system values when the job is
-run. Simple math is also supported on these keywords, so you can perform actions
-like::
-
- size=8*$mb_memory
-
-and get that properly expanded to 8 times the size of memory in the machine.
-
-
-Job file parameters
--------------------
-
-This section describes in details each parameter associated with a job. Some
-parameters take an option of a given type, such as an integer or a
-string. Anywhere a numeric value is required, an arithmetic expression may be
-used, provided it is surrounded by parentheses. Supported operators are:
-
- - addition (+)
- - subtraction (-)
- - multiplication (*)
- - division (/)
- - modulus (%)
- - exponentiation (^)
-
-For time values in expressions, units are microseconds by default. This is
-different than for time values not in expressions (not enclosed in
-parentheses). The following types are used:
-
-
-Parameter types
-~~~~~~~~~~~~~~~
-
-**str**
- String: A sequence of alphanumeric characters.
-
-**time**
- Integer with possible time suffix. Without a unit value is interpreted as
- seconds unless otherwise specified. Accepts a suffix of 'd' for days, 'h' for
- hours, 'm' for minutes, 's' for seconds, 'ms' (or 'msec') for milliseconds and
- 'us' (or 'usec') for microseconds. For example, use 10m for 10 minutes.
-
-.. _int:
-
-**int**
- Integer. A whole number value, which may contain an integer prefix
- and an integer suffix:
-
- [*integer prefix*] **number** [*integer suffix*]
-
- The optional *integer prefix* specifies the number's base. The default
- is decimal. *0x* specifies hexadecimal.
-
- The optional *integer suffix* specifies the number's units, and includes an
- optional unit prefix and an optional unit. For quantities of data, the
- default unit is bytes. For quantities of time, the default unit is seconds
- unless otherwise specified.
-
- With :option:`kb_base`\=1000, fio follows international standards for unit
- prefixes. To specify power-of-10 decimal values defined in the
- International System of Units (SI):
-
- * *K* -- means kilo (K) or 1000
- * *M* -- means mega (M) or 1000**2
- * *G* -- means giga (G) or 1000**3
- * *T* -- means tera (T) or 1000**4
- * *P* -- means peta (P) or 1000**5
-
- To specify power-of-2 binary values defined in IEC 80000-13:
-
- * *Ki* -- means kibi (Ki) or 1024
- * *Mi* -- means mebi (Mi) or 1024**2
- * *Gi* -- means gibi (Gi) or 1024**3
- * *Ti* -- means tebi (Ti) or 1024**4
- * *Pi* -- means pebi (Pi) or 1024**5
-
- For Zone Block Device Mode:
- * *z* -- means Zone
-
- With :option:`kb_base`\=1024 (the default), the unit prefixes are opposite
- from those specified in the SI and IEC 80000-13 standards to provide
- compatibility with old scripts. For example, 4k means 4096.
-
- For quantities of data, an optional unit of 'B' may be included
- (e.g., 'kB' is the same as 'k').
-
- The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega,
- not milli). 'b' and 'B' both mean byte, not bit.
-
- Examples with :option:`kb_base`\=1000:
-
- * *4 KiB*: 4096, 4096b, 4096B, 4ki, 4kib, 4kiB, 4Ki, 4KiB
- * *1 MiB*: 1048576, 1mi, 1024ki
- * *1 MB*: 1000000, 1m, 1000k
- * *1 TiB*: 1099511627776, 1ti, 1024gi, 1048576mi
- * *1 TB*: 1000000000, 1t, 1000m, 1000000k
-
- Examples with :option:`kb_base`\=1024 (default):
-
- * *4 KiB*: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
- * *1 MiB*: 1048576, 1m, 1024k
- * *1 MB*: 1000000, 1mi, 1000ki
- * *1 TiB*: 1099511627776, 1t, 1024g, 1048576m
- * *1 TB*: 1000000000, 1ti, 1000mi, 1000000ki
-
- To specify times (units are not case sensitive):
-
- * *D* -- means days
- * *H* -- means hours
- * *M* -- means minutes
- * *s* -- or sec means seconds (default)
- * *ms* -- or *msec* means milliseconds
- * *us* -- or *usec* means microseconds
-
- If the option accepts an upper and lower range, use a colon ':' or
- minus '-' to separate such values. See :ref:`irange <irange>`.
- If the lower value specified happens to be larger than the upper value
- the two values are swapped.
-
-.. _bool:
-
-**bool**
- Boolean. Usually parsed as an integer, however only defined for
- true and false (1 and 0).
-
-.. _irange:
-
-**irange**
- Integer range with suffix. Allows value range to be given, such as
- 1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the
- option allows two sets of ranges, they can be specified with a ',' or '/'
- delimiter: 1k-4k/8k-32k. Also see :ref:`int <int>`.
-
-**float_list**
- A list of floating point numbers, separated by a ':' character.
-
-With the above in mind, here follows the complete list of fio job parameters.
-
-
-Units
-~~~~~
-
-.. option:: kb_base=int
-
- Select the interpretation of unit prefixes in input parameters.
-
- **1000**
- Inputs comply with IEC 80000-13 and the International
- System of Units (SI). Use:
-
- - power-of-2 values with IEC prefixes (e.g., KiB)
- - power-of-10 values with SI prefixes (e.g., kB)
-
- **1024**
- Compatibility mode (default). To avoid breaking old scripts:
-
- - power-of-2 values with SI prefixes
- - power-of-10 values with IEC prefixes
-
- See :option:`bs` for more details on input parameters.
-
- Outputs always use correct prefixes. Most outputs include both
- side-by-side, like::
-
- bw=2383.3kB/s (2327.4KiB/s)
-
- If only one value is reported, then kb_base selects the one to use:
-
- **1000** -- SI prefixes
-
- **1024** -- IEC prefixes
-
-.. option:: unit_base=int
-
- Base unit for reporting. Allowed values are:
-
- **0**
- Use auto-detection (default).
- **8**
- Byte based.
- **1**
- Bit based.
-
-
-Job description
-~~~~~~~~~~~~~~~
-
-.. option:: name=str
-
- ASCII name of the job. This may be used to override the name printed by fio
- for this job. Otherwise the job name is used. On the command line this
- parameter has the special purpose of also signaling the start of a new job.
-
-.. option:: description=str
-
- Text description of the job. Doesn't do anything except dump this text
- description when this job is run. It's not parsed.
-
-.. option:: loops=int
-
- Run the specified number of iterations of this job. Used to repeat the same
- workload a given number of times. Defaults to 1.
-
-.. option:: numjobs=int
-
- Create the specified number of clones of this job. Each clone of job
- is spawned as an independent thread or process. May be used to setup a
- larger number of threads/processes doing the same thing. Each thread is
- reported separately; to see statistics for all clones as a whole, use
- :option:`group_reporting` in conjunction with :option:`new_group`.
- See :option:`--max-jobs`. Default: 1.
-
-
-Time related parameters
-~~~~~~~~~~~~~~~~~~~~~~~
-
-.. option:: runtime=time
-
- Tell fio to terminate processing after the specified period of time. It
- can be quite hard to determine for how long a specified job will run, so
- this parameter is handy to cap the total runtime to a given time. When
- the unit is omitted, the value is interpreted in seconds.
-
-.. option:: time_based
-
- If set, fio will run for the duration of the :option:`runtime` specified
- even if the file(s) are completely read or written. It will simply loop over
- the same workload as many times as the :option:`runtime` allows.
-
-.. option:: startdelay=irange(time)
-
- Delay the start of job for the specified amount of time. Can be a single
- value or a range. When given as a range, each thread will choose a value
- randomly from within the range. Value is in seconds if a unit is omitted.
-
-.. option:: ramp_time=time
-
- If set, fio will run the specified workload for this amount of time before
- logging any performance numbers. Useful for letting performance settle
- before logging results, thus minimizing the runtime required for stable
- results. Note that the ``ramp_time`` is considered lead in time for a job,
- thus it will increase the total runtime if a special timeout or
- :option:`runtime` is specified. When the unit is omitted, the value is
- given in seconds.
-
-.. option:: clocksource=str
-
- Use the given clocksource as the base of timing. The supported options are:
-
- **gettimeofday**
- :manpage:`gettimeofday(2)`
-
- **clock_gettime**
- :manpage:`clock_gettime(2)`
-
- **cpu**
- Internal CPU clock source
-
- cpu is the preferred clocksource if it is reliable, as it is very fast (and
- fio is heavy on time calls). Fio will automatically use this clocksource if
- it's supported and considered reliable on the system it is running on,
- unless another clocksource is specifically set. For x86/x86-64 CPUs, this
- means supporting TSC Invariant.
-
-.. option:: gtod_reduce=bool
-
- Enable all of the :manpage:`gettimeofday(2)` reducing options
- (:option:`disable_clat`, :option:`disable_slat`, :option:`disable_bw_measurement`) plus
- reduce precision of the timeout somewhat to really shrink the
- :manpage:`gettimeofday(2)` call count. With this option enabled, we only do
- about 0.4% of the :manpage:`gettimeofday(2)` calls we would have done if all
- time keeping was enabled.
-
-.. option:: gtod_cpu=int
-
- Sometimes it's cheaper to dedicate a single thread of execution to just
- getting the current time. Fio (and databases, for instance) are very
- intensive on :manpage:`gettimeofday(2)` calls. With this option, you can set
- one CPU aside for doing nothing but logging current time to a shared memory
- location. Then the other threads/processes that run I/O workloads need only
- copy that segment, instead of entering the kernel with a
- :manpage:`gettimeofday(2)` call. The CPU set aside for doing these time
- calls will be excluded from other uses. Fio will manually clear it from the
- CPU mask of other jobs.
-
-
-Target file/device
-~~~~~~~~~~~~~~~~~~
-
-.. option:: directory=str
-
- Prefix filenames with this directory. Used to place files in a different
- location than :file:`./`. You can specify a number of directories by
- separating the names with a ':' character. These directories will be
- assigned equally distributed to job clones created by :option:`numjobs` as
- long as they are using generated filenames. If specific `filename(s)` are
- set fio will use the first listed directory, and thereby matching the
- `filename` semantic (which generates a file for each clone if not
- specified, but lets all clones use the same file if set).
-
- See the :option:`filename` option for information on how to escape "``:``"
- characters within the directory path itself.
-
- Note: To control the directory fio will use for internal state files
- use :option:`--aux-path`.
-
-.. option:: filename=str
-
- Fio normally makes up a `filename` based on the job name, thread number, and
- file number (see :option:`filename_format`). If you want to share files
- between threads in a job or several
- jobs with fixed file paths, specify a `filename` for each of them to override
- the default. If the ioengine is file based, you can specify a number of files
- by separating the names with a ':' colon. So if you wanted a job to open
- :file:`/dev/sda` and :file:`/dev/sdb` as the two working files, you would use
- ``filename=/dev/sda:/dev/sdb``. This also means that whenever this option is
- specified, :option:`nrfiles` is ignored. The size of regular files specified
- by this option will be :option:`size` divided by number of files unless an
- explicit size is specified by :option:`filesize`.
-
- Each colon in the wanted path must be escaped with a ``\``
- character. For instance, if the path is :file:`/dev/dsk/foo@3,0:c` then you
- would use ``filename=/dev/dsk/foo@3,0\:c`` and if the path is
- :file:`F:\\filename` then you would use ``filename=F\:\filename``.
-
- On Windows, disk devices are accessed as :file:`\\\\.\\PhysicalDrive0` for
- the first device, :file:`\\\\.\\PhysicalDrive1` for the second etc.
- Note: Windows and FreeBSD prevent write access to areas
- of the disk containing in-use data (e.g. filesystems).
-
- The filename "`-`" is a reserved name, meaning *stdin* or *stdout*. Which
- of the two depends on the read/write direction set.
-
-.. option:: filename_format=str
-
- If sharing multiple files between jobs, it is usually necessary to have fio
- generate the exact names that you want. By default, fio will name a file
- based on the default file format specification of
- :file:`jobname.jobnumber.filenumber`. With this option, that can be
- customized. Fio will recognize and replace the following keywords in this
- string:
-
- **$jobname**
- The name of the worker thread or process.
- **$clientuid**
- IP of the fio process when using client/server mode.
- **$jobnum**
- The incremental number of the worker thread or process.
- **$filenum**
- The incremental number of the file for that worker thread or
- process.
-
- To have dependent jobs share a set of files, this option can be set to have
- fio generate filenames that are shared between the two. For instance, if
- :file:`testfiles.$filenum` is specified, file number 4 for any job will be
- named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
- will be used if no other format specifier is given.
-
- If you specify a path then the directories will be created up to the
- main directory for the file. So for example if you specify
- ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
- created before the file setup part of the job. If you specify
- :option:`directory` then the path will be relative that directory,
- otherwise it is treated as the absolute path.
-
-.. option:: unique_filename=bool
-
- To avoid collisions between networked clients, fio defaults to prefixing any
- generated filenames (with a directory specified) with the source of the
- client connecting. To disable this behavior, set this option to 0.
-
-.. option:: opendir=str
-
- Recursively open any files below directory `str`.
-
-.. option:: lockfile=str
-
- Fio defaults to not locking any files before it does I/O to them. If a file
- or file descriptor is shared, fio can serialize I/O to that file to make the
- end result consistent. This is usual for emulating real workloads that share
- files. The lock modes are:
-
- **none**
- No locking. The default.
- **exclusive**
- Only one thread or process may do I/O at a time, excluding all
- others.
- **readwrite**
- Read-write locking on the file. Many readers may
- access the file at the same time, but writes get exclusive access.
-
-.. option:: nrfiles=int
-
- Number of files to use for this job. Defaults to 1. The size of files
- will be :option:`size` divided by this unless explicit size is specified by
- :option:`filesize`. Files are created for each thread separately, and each
- file will have a file number within its name by default, as explained in
- :option:`filename` section.
-
-
-.. option:: openfiles=int
-
- Number of files to keep open at the same time. Defaults to the same as
- :option:`nrfiles`, can be set smaller to limit the number simultaneous
- opens.
-
-.. option:: file_service_type=str
-
- Defines how fio decides which file from a job to service next. The following
- types are defined:
-
- **random**
- Choose a file at random.
-
- **roundrobin**
- Round robin over opened files. This is the default.
-
- **sequential**
- Finish one file before moving on to the next. Multiple files can
- still be open depending on :option:`openfiles`.
-
- **zipf**
- Use a *Zipf* distribution to decide what file to access.
-
- **pareto**
- Use a *Pareto* distribution to decide what file to access.
-
- **normal**
- Use a *Gaussian* (normal) distribution to decide what file to
- access.
-
- **gauss**
- Alias for normal.
-
- For *random*, *roundrobin*, and *sequential*, a postfix can be appended to
- tell fio how many I/Os to issue before switching to a new file. For example,
- specifying ``file_service_type=random:8`` would cause fio to issue
- 8 I/Os before selecting a new file at random. For the non-uniform
- distributions, a floating point postfix can be given to influence how the
- distribution is skewed. See :option:`random_distribution` for a description
- of how that would work.
-
-.. option:: ioscheduler=str
-
- Attempt to switch the device hosting the file to the specified I/O scheduler
- before running.
-
-.. option:: create_serialize=bool
-
- If true, serialize the file creation for the jobs. This may be handy to
- avoid interleaving of data files, which may greatly depend on the filesystem
- used and even the number of processors in the system. Default: true.
-
-.. option:: create_fsync=bool
-
- :manpage:`fsync(2)` the data file after creation. This is the default.
-
-.. option:: create_on_open=bool
-
- If true, don't pre-create files but allow the job's open() to create a file
- when it's time to do I/O. Default: false -- pre-create all necessary files
- when the job starts.
-
-.. option:: create_only=bool
-
- If true, fio will only run the setup phase of the job. If files need to be
- laid out or updated on disk, only that will be done -- the actual job contents
- are not executed. Default: false.
-
-.. option:: allow_file_create=bool
-
- If true, fio is permitted to create files as part of its workload. If this
- option is false, then fio will error out if
- the files it needs to use don't already exist. Default: true.
-
-.. option:: allow_mounted_write=bool
-
- If this isn't set, fio will abort jobs that are destructive (e.g. that write)
- to what appears to be a mounted device or partition. This should help catch
- creating inadvertently destructive tests, not realizing that the test will
- destroy data on the mounted file system. Note that some platforms don't allow
- writing against a mounted device regardless of this option. Default: false.
-
-.. option:: pre_read=bool
-
- If this is given, files will be pre-read into memory before starting the
- given I/O operation. This will also clear the :option:`invalidate` flag,
- since it is pointless to pre-read and then drop the cache. This will only
- work for I/O engines that are seek-able, since they allow you to read the
- same data multiple times. Thus it will not work on non-seekable I/O engines
- (e.g. network, splice). Default: false.
-
-.. option:: unlink=bool
-
- Unlink the job files when done. Not the default, as repeated runs of that
- job would then waste time recreating the file set again and again. Default:
- false.
-
-.. option:: unlink_each_loop=bool
-
- Unlink job files after each iteration or loop. Default: false.
-
-.. option:: zonemode=str
-
- Accepted values are:
-
- **none**
- The :option:`zonerange`, :option:`zonesize`,
- :option `zonecapacity` and option:`zoneskip`
- parameters are ignored.
- **strided**
- I/O happens in a single zone until
- :option:`zonesize` bytes have been transferred.
- After that number of bytes has been
- transferred processing of the next zone
- starts. :option `zonecapacity` is ignored.
- **zbd**
- Zoned block device mode. I/O happens
- sequentially in each zone, even if random I/O
- has been selected. Random I/O happens across
- all zones instead of being restricted to a
- single zone. The :option:`zoneskip` parameter
- is ignored. :option:`zonerange` and
- :option:`zonesize` must be identical.
- Trim is handled using a zone reset operation.
- Trim only considers non-empty sequential write
- required and sequential write preferred zones.
-
-.. option:: zonerange=int
-
- Size of a single zone. See also :option:`zonesize` and
- :option:`zoneskip`.
-
-.. option:: zonesize=int
-
- For :option:`zonemode` =strided, this is the number of bytes to
- transfer before skipping :option:`zoneskip` bytes. If this parameter
- is smaller than :option:`zonerange` then only a fraction of each zone
- with :option:`zonerange` bytes will be accessed. If this parameter is
- larger than :option:`zonerange` then each zone will be accessed
- multiple times before skipping to the next zone.
-
- For :option:`zonemode` =zbd, this is the size of a single zone. The
- :option:`zonerange` parameter is ignored in this mode.
-
-
-.. option:: zonecapacity=int
-
- For :option:`zonemode` =zbd, this defines the capacity of a single zone,
- which is the accessible area starting from the zone start address.
- This parameter only applies when using :option:`zonemode` =zbd in
- combination with regular block devices. If not specified it defaults to
- the zone size. If the target device is a zoned block device, the zone
- capacity is obtained from the device information and this option is
- ignored.
-
-.. option:: zoneskip=int
-
- For :option:`zonemode` =strided, the number of bytes to skip after
- :option:`zonesize` bytes of data have been transferred. This parameter
- must be zero for :option:`zonemode` =zbd.
-
-.. option:: read_beyond_wp=bool
-
- This parameter applies to :option:`zonemode` =zbd only.
-
- Zoned block devices are block devices that consist of multiple zones.
- Each zone has a type, e.g. conventional or sequential. A conventional
- zone can be written at any offset that is a multiple of the block
- size. Sequential zones must be written sequentially. The position at
- which a write must occur is called the write pointer. A zoned block
- device can be either drive managed, host managed or host aware. For
- host managed devices the host must ensure that writes happen
- sequentially. Fio recognizes host managed devices and serializes
- writes to sequential zones for these devices.
-
- If a read occurs in a sequential zone beyond the write pointer then
- the zoned block device will complete the read without reading any data
- from the storage medium. Since such reads lead to unrealistically high
- bandwidth and IOPS numbers fio only reads beyond the write pointer if
- explicitly told to do so. Default: false.
-
-.. option:: max_open_zones=int
-
- When running a random write test across an entire drive many more
- zones will be open than in a typical application workload. Hence this
- command line option that allows to limit the number of open zones. The
- number of open zones is defined as the number of zones to which write
- commands are issued.
-
-.. option:: job_max_open_zones=int
-
- Limit on the number of simultaneously opened zones per single
- thread/process.
-
-.. option:: ignore_zone_limits=bool
- If this option is used, fio will ignore the maximum number of open
- zones limit of the zoned block device in use, thus allowing the
- option :option:`max_open_zones` value to be larger than the device
- reported limit. Default: false.
-
-.. option:: zone_reset_threshold=float
-
- A number between zero and one that indicates the ratio of logical
- blocks with data to the total number of logical blocks in the test
- above which zones should be reset periodically.
-
-.. option:: zone_reset_frequency=float
-
- A number between zero and one that indicates how often a zone reset
- should be issued if the zone reset threshold has been exceeded. A zone
- reset is submitted after each (1 / zone_reset_frequency) write
- requests. This and the previous parameter can be used to simulate
- garbage collection activity.
-
-
-I/O type
-~~~~~~~~
-
-.. option:: direct=bool
-
- If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that
- OpenBSD and ZFS on Solaris don't support direct I/O. On Windows the synchronous
- ioengines don't support direct I/O. Default: false.
-
-.. option:: atomic=bool
-
- If value is true, attempt to use atomic direct I/O. Atomic writes are
- guaranteed to be stable once acknowledged by the operating system. Only
- Linux supports O_ATOMIC right now.
-
-.. option:: buffered=bool
-
- If value is true, use buffered I/O. This is the opposite of the
- :option:`direct` option. Defaults to true.
-
-.. option:: readwrite=str, rw=str
-
- Type of I/O pattern. Accepted values are:
-
- **read**
- Sequential reads.
- **write**
- Sequential writes.
- **trim**
- Sequential trims (Linux block devices and SCSI
- character devices only).
- **randread**
- Random reads.
- **randwrite**
- Random writes.
- **randtrim**
- Random trims (Linux block devices and SCSI
- character devices only).
- **rw,readwrite**
- Sequential mixed reads and writes.
- **randrw**
- Random mixed reads and writes.
- **trimwrite**
- Sequential trim+write sequences. Blocks will be trimmed first,
- then the same blocks will be written to.
-
- Fio defaults to read if the option is not specified. For the mixed I/O
- types, the default is to split them 50/50. For certain types of I/O the
- result may still be skewed a bit, since the speed may be different.
-
- It is possible to specify the number of I/Os to do before getting a new
- offset by appending ``:<nr>`` to the end of the string given. For a
- random read, it would look like ``rw=randread:8`` for passing in an offset
- modifier with a value of 8. If the suffix is used with a sequential I/O
- pattern, then the *<nr>* value specified will be **added** to the generated
- offset for each I/O turning sequential I/O into sequential I/O with holes.
- For instance, using ``rw=write:4k`` will skip 4k for every write. Also see
- the :option:`rw_sequencer` option.
-
-.. option:: rw_sequencer=str
-
- If an offset modifier is given by appending a number to the ``rw=<str>``
- line, then this option controls how that number modifies the I/O offset
- being generated. Accepted values are:
-
- **sequential**
- Generate sequential offset.
- **identical**
- Generate the same offset.
-
- ``sequential`` is only useful for random I/O, where fio would normally
- generate a new random offset for every I/O. If you append e.g. 8 to randread,
- you would get a new random offset for every 8 I/Os. The result would be a
- seek for only every 8 I/Os, instead of for every I/O. Use ``rw=randread:8``
- to specify that. As sequential I/O is already sequential, setting
- ``sequential`` for that would not result in any differences. ``identical``
- behaves in a similar fashion, except it sends the same offset 8 number of
- times before generating a new offset.
-
-.. option:: unified_rw_reporting=str
-
- Fio normally reports statistics on a per data direction basis, meaning that
- reads, writes, and trims are accounted and reported separately. This option
- determines whether fio reports the results normally, summed together, or as
- both options.
- Accepted values are:
-
- **none**
- Normal statistics reporting.
-
- **mixed**
- Statistics are summed per data direction and reported together.
-
- **both**
- Statistics are reported normally, followed by the mixed statistics.
-
- **0**
- Backward-compatible alias for **none**.
-
- **1**
- Backward-compatible alias for **mixed**.
-
- **2**
- Alias for **both**.
-
-.. option:: randrepeat=bool
-
- Seed the random number generator used for random I/O patterns in a
- predictable way so the pattern is repeatable across runs. Default: true.
-
-.. option:: allrandrepeat=bool
-
- Seed all random number generators in a predictable way so results are
- repeatable across runs. Default: false.
-
-.. option:: randseed=int
-
- Seed the random number generators based on this seed value, to be able to
- control what sequence of output is being generated. If not set, the random
- sequence depends on the :option:`randrepeat` setting.
-
-.. option:: fallocate=str
-
- Whether pre-allocation is performed when laying down files.
- Accepted values are:
-
- **none**
- Do not pre-allocate space.
-
- **native**
- Use a platform's native pre-allocation call but fall back to
- **none** behavior if it fails/is not implemented.
-
- **posix**
- Pre-allocate via :manpage:`posix_fallocate(3)`.
-
- **keep**
- Pre-allocate via :manpage:`fallocate(2)` with
- FALLOC_FL_KEEP_SIZE set.
-
- **truncate**
- Extend file to final size via :manpage:`ftruncate(2)`
- instead of allocating.
-
- **0**
- Backward-compatible alias for **none**.
-
- **1**
- Backward-compatible alias for **posix**.
-
- May not be available on all supported platforms. **keep** is only available
- on Linux. If using ZFS on Solaris this cannot be set to **posix**
- because ZFS doesn't support pre-allocation. Default: **native** if any
- pre-allocation methods except **truncate** are available, **none** if not.
-
- Note that using **truncate** on Windows will interact surprisingly
- with non-sequential write patterns. When writing to a file that has
- been extended by setting the end-of-file information, Windows will
- backfill the unwritten portion of the file up to that offset with
- zeroes before issuing the new write. This means that a single small
- write to the end of an extended file will stall until the entire
- file has been filled with zeroes.
-
-.. option:: fadvise_hint=str
-
- Use :manpage:`posix_fadvise(2)` or :manpage:`posix_fadvise(2)` to
- advise the kernel on what I/O patterns are likely to be issued.
- Accepted values are:
-
- **0**
- Backwards-compatible hint for "no hint".
-
- **1**
- Backwards compatible hint for "advise with fio workload type". This
- uses **FADV_RANDOM** for a random workload, and **FADV_SEQUENTIAL**
- for a sequential workload.
-
- **sequential**
- Advise using **FADV_SEQUENTIAL**.
-
- **random**
- Advise using **FADV_RANDOM**.
-
-.. option:: write_hint=str
-
- Use :manpage:`fcntl(2)` to advise the kernel what life time to expect
- from a write. Only supported on Linux, as of version 4.13. Accepted
- values are:
-
- **none**
- No particular life time associated with this file.
-
- **short**
- Data written to this file has a short life time.
-
- **medium**
- Data written to this file has a medium life time.
-
- **long**
- Data written to this file has a long life time.
-
- **extreme**
- Data written to this file has a very long life time.
-
- The values are all relative to each other, and no absolute meaning
- should be associated with them.
-
-.. option:: offset=int
-
- Start I/O at the provided offset in the file, given as either a fixed size in
- bytes, zones or a percentage. If a percentage is given, the generated offset will be
- aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
- provided. Data before the given offset will not be touched. This
- effectively caps the file size at `real_size - offset`. Can be combined with
- :option:`size` to constrain the start and end range of the I/O workload.
- A percentage can be specified by a number between 1 and 100 followed by '%',
- for example, ``offset=20%`` to specify 20%. In ZBD mode, value can be set as
- number of zones using 'z'.
-
-.. option:: offset_align=int
-
- If set to non-zero value, the byte offset generated by a percentage ``offset``
- is aligned upwards to this value. Defaults to 0 meaning that a percentage
- offset is aligned to the minimum block size.
-
-.. option:: offset_increment=int
-
- If this is provided, then the real offset becomes `offset + offset_increment
- * thread_number`, where the thread number is a counter that starts at 0 and
- is incremented for each sub-job (i.e. when :option:`numjobs` option is
- specified). This option is useful if there are several jobs which are
- intended to operate on a file in parallel disjoint segments, with even
- spacing between the starting points. Percentages can be used for this option.
- If a percentage is given, the generated offset will be aligned to the minimum
- ``blocksize`` or to the value of ``offset_align`` if provided. In ZBD mode, value can
- also be set as number of zones using 'z'.
-
-.. option:: number_ios=int
-
- Fio will normally perform I/Os until it has exhausted the size of the region
- set by :option:`size`, or if it exhaust the allocated time (or hits an error
- condition). With this setting, the range/size can be set independently of
- the number of I/Os to perform. When fio reaches this number, it will exit
- normally and report status. Note that this does not extend the amount of I/O
- that will be done, it will only stop fio if this condition is met before
- other end-of-job criteria.
-
-.. option:: fsync=int
-
- If writing to a file, issue an :manpage:`fsync(2)` (or its equivalent) of
- the dirty data for every number of blocks given. For example, if you give 32
- as a parameter, fio will sync the file after every 32 writes issued. If fio is
- using non-buffered I/O, we may not sync the file. The exception is the sg
- I/O engine, which synchronizes the disk cache anyway. Defaults to 0, which
- means fio does not periodically issue and wait for a sync to complete. Also
- see :option:`end_fsync` and :option:`fsync_on_close`.
-
-.. option:: fdatasync=int
-
- Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and
- not metadata blocks. In Windows, DragonFlyBSD or OSX there is no
- :manpage:`fdatasync(2)` so this falls back to using :manpage:`fsync(2)`.
- Defaults to 0, which means fio does not periodically issue and wait for a
- data-only sync to complete.
-
-.. option:: write_barrier=int
-
- Make every `N-th` write a barrier write.
-
-.. option:: sync_file_range=str:int
-
- Use :manpage:`sync_file_range(2)` for every `int` number of write
- operations. Fio will track range of writes that have happened since the last
- :manpage:`sync_file_range(2)` call. `str` can currently be one or more of:
-
- **wait_before**
- SYNC_FILE_RANGE_WAIT_BEFORE
- **write**
- SYNC_FILE_RANGE_WRITE
- **wait_after**
- SYNC_FILE_RANGE_WAIT_AFTER
-
- So if you do ``sync_file_range=wait_before,write:8``, fio would use
- ``SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE`` for every 8
- writes. Also see the :manpage:`sync_file_range(2)` man page. This option is
- Linux specific.
-
-.. option:: overwrite=bool
-
- If true, writes to a file will always overwrite existing data. If the file
- doesn't already exist, it will be created before the write phase begins. If
- the file exists and is large enough for the specified write phase, nothing
- will be done. Default: false.
-
-.. option:: end_fsync=bool
-
- If true, :manpage:`fsync(2)` file contents when a write stage has completed.
- Default: false.
-
-.. option:: fsync_on_close=bool
-
- If true, fio will :manpage:`fsync(2)` a dirty file on close. This differs
- from :option:`end_fsync` in that it will happen on every file close, not
- just at the end of the job. Default: false.
-
-.. option:: rwmixread=int
-
- Percentage of a mixed workload that should be reads. Default: 50.
-
-.. option:: rwmixwrite=int
-
- Percentage of a mixed workload that should be writes. If both
- :option:`rwmixread` and :option:`rwmixwrite` is given and the values do not
- add up to 100%, the latter of the two will be used to override the
- first. This may interfere with a given rate setting, if fio is asked to
- limit reads or writes to a certain rate. If that is the case, then the
- distribution may be skewed. Default: 50.
-
-.. option:: random_distribution=str:float[:float][,str:float][,str:float]
-
- By default, fio will use a completely uniform random distribution when asked
- to perform random I/O. Sometimes it is useful to skew the distribution in
- specific ways, ensuring that some parts of the data is more hot than others.
- fio includes the following distribution models:
-
- **random**
- Uniform random distribution
-
- **zipf**
- Zipf distribution
-
- **pareto**
- Pareto distribution
-
- **normal**
- Normal (Gaussian) distribution
-
- **zoned**
- Zoned random distribution
-
- **zoned_abs**
- Zone absolute random distribution
-
- When using a **zipf** or **pareto** distribution, an input value is also
- needed to define the access pattern. For **zipf**, this is the `Zipf
- theta`. For **pareto**, it's the `Pareto power`. Fio includes a test
- program, :command:`fio-genzipf`, that can be used visualize what the given input
- values will yield in terms of hit rates. If you wanted to use **zipf** with
- a `theta` of 1.2, you would use ``random_distribution=zipf:1.2`` as the
- option. If a non-uniform model is used, fio will disable use of the random
- map. For the **normal** distribution, a normal (Gaussian) deviation is
- supplied as a value between 0 and 100.
-
- The second, optional float is allowed for **pareto**, **zipf** and **normal** distributions.
- It allows to set base of distribution in non-default place, giving more control
- over most probable outcome. This value is in range [0-1] which maps linearly to
- range of possible random values.
- Defaults are: random for **pareto** and **zipf**, and 0.5 for **normal**.
- If you wanted to use **zipf** with a `theta` of 1.2 centered on 1/4 of allowed value range,
- you would use ``random_distibution=zipf:1.2:0.25``.
-
- For a **zoned** distribution, fio supports specifying percentages of I/O
- access that should fall within what range of the file or device. For
- example, given a criteria of:
-
- * 60% of accesses should be to the first 10%
- * 30% of accesses should be to the next 20%
- * 8% of accesses should be to the next 30%
- * 2% of accesses should be to the next 40%
-
- we can define that through zoning of the random accesses. For the above
- example, the user would do::
-
- random_distribution=zoned:60/10:30/20:8/30:2/40
-
- A **zoned_abs** distribution works exactly like the **zoned**, except
- that it takes absolute sizes. For example, let's say you wanted to
- define access according to the following criteria:
-
- * 60% of accesses should be to the first 20G
- * 30% of accesses should be to the next 100G
- * 10% of accesses should be to the next 500G
-
- we can define an absolute zoning distribution with:
-
- random_distribution=zoned_abs=60/20G:30/100G:10/500g
-
- For both **zoned** and **zoned_abs**, fio supports defining up to
- 256 separate zones.
-
- Similarly to how :option:`bssplit` works for setting ranges and
- percentages of block sizes. Like :option:`bssplit`, it's possible to
- specify separate zones for reads, writes, and trims. If just one set
- is given, it'll apply to all of them. This goes for both **zoned**
- **zoned_abs** distributions.
-
-.. option:: percentage_random=int[,int][,int]
-
- For a random workload, set how big a percentage should be random. This
- defaults to 100%, in which case the workload is fully random. It can be set
- from anywhere from 0 to 100. Setting it to 0 would make the workload fully
- sequential. Any setting in between will result in a random mix of sequential
- and random I/O, at the given percentages. Comma-separated values may be
- specified for reads, writes, and trims as described in :option:`blocksize`.
-
-.. option:: norandommap
-
- Normally fio will cover every block of the file when doing random I/O. If
- this option is given, fio will just get a new random offset without looking
- at past I/O history. This means that some blocks may not be read or written,
- and that some blocks may be read/written more than once. If this option is
- used with :option:`verify` and multiple blocksizes (via :option:`bsrange`),
- only intact blocks are verified, i.e., partially-overwritten blocks are
- ignored. With an async I/O engine and an I/O depth > 1, it is possible for
- the same block to be overwritten, which can cause verification errors. Either
- do not use norandommap in this case, or also use the lfsr random generator.
-
-.. option:: softrandommap=bool
-
- See :option:`norandommap`. If fio runs with the random block map enabled and
- it fails to allocate the map, if this option is set it will continue without
- a random block map. As coverage will not be as complete as with random maps,
- this option is disabled by default.
-
-.. option:: random_generator=str
-
- Fio supports the following engines for generating I/O offsets for random I/O:
-
- **tausworthe**
- Strong 2^88 cycle random number generator.
- **lfsr**
- Linear feedback shift register generator.
- **tausworthe64**
- Strong 64-bit 2^258 cycle random number generator.
-
- **tausworthe** is a strong random number generator, but it requires tracking
- on the side if we want to ensure that blocks are only read or written
- once. **lfsr** guarantees that we never generate the same offset twice, and
- it's also less computationally expensive. It's not a true random generator,
- however, though for I/O purposes it's typically good enough. **lfsr** only
- works with single block sizes, not with workloads that use multiple block
- sizes. If used with such a workload, fio may read or write some blocks
- multiple times. The default value is **tausworthe**, unless the required
- space exceeds 2^32 blocks. If it does, then **tausworthe64** is
- selected automatically.
-
-
-Block size
-~~~~~~~~~~
-
-.. option:: blocksize=int[,int][,int], bs=int[,int][,int]
-
- The block size in bytes used for I/O units. Default: 4096. A single value
- applies to reads, writes, and trims. Comma-separated values may be
- specified for reads, writes, and trims. A value not terminated in a comma
- applies to subsequent types.
-
- Examples:
-
- **bs=256k**
- means 256k for reads, writes and trims.
-
- **bs=8k,32k**
- means 8k for reads, 32k for writes and trims.
-
- **bs=8k,32k,**
- means 8k for reads, 32k for writes, and default for trims.
-
- **bs=,8k**
- means default for reads, 8k for writes and trims.
-
- **bs=,8k,**
- means default for reads, 8k for writes, and default for trims.
-
-.. option:: blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
-
- A range of block sizes in bytes for I/O units. The issued I/O unit will
- always be a multiple of the minimum size, unless
- :option:`blocksize_unaligned` is set.
-
- Comma-separated ranges may be specified for reads, writes, and trims as
- described in :option:`blocksize`.
-
- Example: ``bsrange=1k-4k,2k-8k``.
-
-.. option:: bssplit=str[,str][,str]
-
- Sometimes you want even finer grained control of the block sizes
- issued, not just an even split between them. This option allows you to
- weight various block sizes, so that you are able to define a specific
- amount of block sizes issued. The format for this option is::
-
- bssplit=blocksize/percentage:blocksize/percentage
-
- for as many block sizes as needed. So if you want to define a workload
- that has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you would
- write::
-
- bssplit=4k/10:64k/50:32k/40
-
- Ordering does not matter. If the percentage is left blank, fio will
- fill in the remaining values evenly. So a bssplit option like this one::
-
- bssplit=4k/50:1k/:32k/
-
- would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always
- add up to 100, if bssplit is given a range that adds up to more, it
- will error out.
-
- Comma-separated values may be specified for reads, writes, and trims as
- described in :option:`blocksize`.
-
- If you want a workload that has 50% 2k reads and 50% 4k reads, while
- having 90% 4k writes and 10% 8k writes, you would specify::
-
- bssplit=2k/50:4k/50,4k/90:8k/10
-
- Fio supports defining up to 64 different weights for each data
- direction.
-
-.. option:: blocksize_unaligned, bs_unaligned
-
- If set, fio will issue I/O units with any size within
- :option:`blocksize_range`, not just multiples of the minimum size. This
- typically won't work with direct I/O, as that normally requires sector
- alignment.
-
-.. option:: bs_is_seq_rand=bool
-
- If this option is set, fio will use the normal read,write blocksize settings
- as sequential,random blocksize settings instead. Any random read or write
- will use the WRITE blocksize settings, and any sequential read or write will
- use the READ blocksize settings.
-
-.. option:: blockalign=int[,int][,int], ba=int[,int][,int]
-
- Boundary to which fio will align random I/O units. Default:
- :option:`blocksize`. Minimum alignment is typically 512b for using direct
- I/O, though it usually depends on the hardware block size. This option is
- mutually exclusive with using a random map for files, so it will turn off
- that option. Comma-separated values may be specified for reads, writes, and
- trims as described in :option:`blocksize`.
-
-
-Buffers and memory
-~~~~~~~~~~~~~~~~~~
-
-.. option:: zero_buffers
-
- Initialize buffers with all zeros. Default: fill buffers with random data.
-
-.. option:: refill_buffers
-
- If this option is given, fio will refill the I/O buffers on every
- submit. Only makes sense if :option:`zero_buffers` isn't specified,
- naturally. Defaults to being unset i.e., the buffer is only filled at
- init time and the data in it is reused when possible but if any of
- :option:`verify`, :option:`buffer_compress_percentage` or
- :option:`dedupe_percentage` are enabled then `refill_buffers` is also
- automatically enabled.
-
-.. option:: scramble_buffers=bool
-
- If :option:`refill_buffers` is too costly and the target is using data
- deduplication, then setting this option will slightly modify the I/O buffer
- contents to defeat normal de-dupe attempts. This is not enough to defeat
- more clever block compression attempts, but it will stop naive dedupe of
- blocks. Default: true.
-
-.. option:: buffer_compress_percentage=int
-
- If this is set, then fio will attempt to provide I/O buffer content
- (on WRITEs) that compresses to the specified level. Fio does this by
- providing a mix of random data followed by fixed pattern data. The
- fixed pattern is either zeros, or the pattern specified by
- :option:`buffer_pattern`. If the `buffer_pattern` option is used, it
- might skew the compression ratio slightly. Setting
- `buffer_compress_percentage` to a value other than 100 will also
- enable :option:`refill_buffers` in order to reduce the likelihood that
- adjacent blocks are so similar that they over compress when seen
- together. See :option:`buffer_compress_chunk` for how to set a finer or
- coarser granularity for the random/fixed data region. Defaults to unset
- i.e., buffer data will not adhere to any compression level.
-
-.. option:: buffer_compress_chunk=int
-
- This setting allows fio to manage how big the random/fixed data region
- is when using :option:`buffer_compress_percentage`. When
- `buffer_compress_chunk` is set to some non-zero value smaller than the
- block size, fio can repeat the random/fixed region throughout the I/O
- buffer at the specified interval (which particularly useful when
- bigger block sizes are used for a job). When set to 0, fio will use a
- chunk size that matches the block size resulting in a single
- random/fixed region within the I/O buffer. Defaults to 512. When the
- unit is omitted, the value is interpreted in bytes.
-
-.. option:: buffer_pattern=str
-
- If set, fio will fill the I/O buffers with this pattern or with the contents
- of a file. If not set, the contents of I/O buffers are defined by the other
- options related to buffer contents. The setting can be any pattern of bytes,
- and can be prefixed with 0x for hex values. It may also be a string, where
- the string must then be wrapped with ``""``. Or it may also be a filename,
- where the filename must be wrapped with ``''`` in which case the file is
- opened and read. Note that not all the file contents will be read if that
- would cause the buffers to overflow. So, for example::
-
- buffer_pattern='filename'
-
- or::
-
- buffer_pattern="abcd"
-
- or::
-
- buffer_pattern=-12
-
- or::
-
- buffer_pattern=0xdeadface
-
- Also you can combine everything together in any order::
-
- buffer_pattern=0xdeadface"abcd"-12'filename'
-
-.. option:: dedupe_percentage=int
-
- If set, fio will generate this percentage of identical buffers when
- writing. These buffers will be naturally dedupable. The contents of the
- buffers depend on what other buffer compression settings have been set. It's
- possible to have the individual buffers either fully compressible, or not at
- all -- this option only controls the distribution of unique buffers. Setting
- this option will also enable :option:`refill_buffers` to prevent every buffer
- being identical.
-
-.. option:: dedupe_mode=str
-
- If ``dedupe_percentage=<int>`` is given, then this option controls how fio
- generates the dedupe buffers.
-
- **repeat**
- Generate dedupe buffers by repeating previous writes
- **working_set**
- Generate dedupe buffers from working set
-
- ``repeat`` is the default option for fio. Dedupe buffers are generated
- by repeating previous unique write.
-
- ``working_set`` is a more realistic workload.
- With ``working_set``, ``dedupe_working_set_percentage=<int>`` should be provided.
- Given that, fio will use the initial unique write buffers as its working set.
- Upon deciding to dedupe, fio will randomly choose a buffer from the working set.
- Note that by using ``working_set`` the dedupe percentage will converge
- to the desired over time while ``repeat`` maintains the desired percentage
- throughout the job.
-
-.. option:: dedupe_working_set_percentage=int
-
- If ``dedupe_mode=<str>`` is set to ``working_set``, then this controls
- the percentage of size of the file or device used as the buffers
- fio will choose to generate the dedupe buffers from
-
- Note that size needs to be explicitly provided and only 1 file per
- job is supported
-
-.. option:: invalidate=bool
-
- Invalidate the buffer/page cache parts of the files to be used prior to
- starting I/O if the platform and file type support it. Defaults to true.
- This will be ignored if :option:`pre_read` is also specified for the
- same job.
-
-.. option:: sync=str
-
- Whether, and what type, of synchronous I/O to use for writes. The allowed
- values are:
-
- **none**
- Do not use synchronous IO, the default.
-
- **0**
- Same as **none**.
-
- **sync**
- Use synchronous file IO. For the majority of I/O engines,
- this means using O_SYNC.
-
- **1**
- Same as **sync**.
-
- **dsync**
- Use synchronous data IO. For the majority of I/O engines,
- this means using O_DSYNC.
-
-
-.. option:: iomem=str, mem=str
-
- Fio can use various types of memory as the I/O unit buffer. The allowed
- values are:
-
- **malloc**
- Use memory from :manpage:`malloc(3)` as the buffers. Default memory
- type.
-
- **shm**
- Use shared memory as the buffers. Allocated through
- :manpage:`shmget(2)`.
-
- **shmhuge**
- Same as shm, but use huge pages as backing.
-
- **mmap**
- Use :manpage:`mmap(2)` to allocate buffers. May either be anonymous memory, or can
- be file backed if a filename is given after the option. The format
- is `mem=mmap:/path/to/file`.
-
- **mmaphuge**
- Use a memory mapped huge file as the buffer backing. Append filename
- after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file`.
-
- **mmapshared**
- Same as mmap, but use a MMAP_SHARED mapping.
-
- **cudamalloc**
- Use GPU memory as the buffers for GPUDirect RDMA benchmark.
- The :option:`ioengine` must be `rdma`.
-
- The area allocated is a function of the maximum allowed bs size for the job,
- multiplied by the I/O depth given. Note that for **shmhuge** and
- **mmaphuge** to work, the system must have free huge pages allocated. This
- can normally be checked and set by reading/writing
- :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page
- is 4MiB in size. So to calculate the number of huge pages you need for a
- given job file, add up the I/O depth of all jobs (normally one unless
- :option:`iodepth` is used) and multiply by the maximum bs set. Then divide
- that number by the huge page size. You can see the size of the huge pages in
- :file:`/proc/meminfo`. If no huge pages are allocated by having a non-zero
- number in `nr_hugepages`, using **mmaphuge** or **shmhuge** will fail. Also
- see :option:`hugepage-size`.
-
- **mmaphuge** also needs to have hugetlbfs mounted and the file location
- should point there. So if it's mounted in :file:`/huge`, you would use
- `mem=mmaphuge:/huge/somefile`.
-
-.. option:: iomem_align=int, mem_align=int
-
- This indicates the memory alignment of the I/O memory buffers. Note that
- the given alignment is applied to the first I/O unit buffer, if using
- :option:`iodepth` the alignment of the following buffers are given by the
- :option:`bs` used. In other words, if using a :option:`bs` that is a
- multiple of the page sized in the system, all buffers will be aligned to
- this value. If using a :option:`bs` that is not page aligned, the alignment
- of subsequent I/O memory buffers is the sum of the :option:`iomem_align` and
- :option:`bs` used.
-
-.. option:: hugepage-size=int
-
- Defines the size of a huge page. Must at least be equal to the system
- setting, see :file:`/proc/meminfo`. Defaults to 4MiB. Should probably
- always be a multiple of megabytes, so using ``hugepage-size=Xm`` is the
- preferred way to set this to avoid setting a non-pow-2 bad value.
-
-.. option:: lockmem=int
-
- Pin the specified amount of memory with :manpage:`mlock(2)`. Can be used to
- simulate a smaller amount of memory. The amount specified is per worker.
-
-
-I/O size
-~~~~~~~~
-
-.. option:: size=int
-
- The total size of file I/O for each thread of this job. Fio will run until
- this many bytes has been transferred, unless runtime is limited by other options
- (such as :option:`runtime`, for instance, or increased/decreased by :option:`io_size`).
- Fio will divide this size between the available files determined by options
- such as :option:`nrfiles`, :option:`filename`, unless :option:`filesize` is
- specified by the job. If the result of division happens to be 0, the size is
- set to the physical size of the given files or devices if they exist.
- If this option is not specified, fio will use the full size of the given
- files or devices. If the files do not exist, size must be given. It is also
- possible to give size as a percentage between 1 and 100. If ``size=20%`` is
- given, fio will use 20% of the full size of the given files or devices.
- In ZBD mode, value can also be set as number of zones using 'z'.
- Can be combined with :option:`offset` to constrain the start and end range
- that I/O will be done within.
-
-.. option:: io_size=int, io_limit=int
-
- Normally fio operates within the region set by :option:`size`, which means
- that the :option:`size` option sets both the region and size of I/O to be
- performed. Sometimes that is not what you want. With this option, it is
- possible to define just the amount of I/O that fio should do. For instance,
- if :option:`size` is set to 20GiB and :option:`io_size` is set to 5GiB, fio
- will perform I/O within the first 20GiB but exit when 5GiB have been
- done. The opposite is also possible -- if :option:`size` is set to 20GiB,
- and :option:`io_size` is set to 40GiB, then fio will do 40GiB of I/O within
- the 0..20GiB region.
-
-.. option:: filesize=irange(int)
-
- Individual file sizes. May be a range, in which case fio will select sizes for
- files at random within the given range. If not given, each created file is the
- same size. This option overrides :option:`size` in terms of file size, i.e. if
- :option:`filesize` is specified then :option:`size` becomes merely the default
- for :option:`io_size` and has no effect at all if :option:`io_size` is set
- explicitly.
-
-.. option:: file_append=bool
-
- Perform I/O after the end of the file. Normally fio will operate within the
- size of a file. If this option is set, then fio will append to the file
- instead. This has identical behavior to setting :option:`offset` to the size
- of a file. This option is ignored on non-regular files.
-
-.. option:: fill_device=bool, fill_fs=bool
-
- Sets size to something really large and waits for ENOSPC (no space left on
- device) or EDQUOT (disk quota exceeded)
- as the terminating condition. Only makes sense with sequential
- write. For a read workload, the mount point will be filled first then I/O
- started on the result. This option doesn't make sense if operating on a raw
- device node, since the size of that is already known by the file system.
- Additionally, writing beyond end-of-device will not return ENOSPC there.
-
-
-I/O engine
-~~~~~~~~~~
-
-.. option:: ioengine=str
-
- Defines how the job issues I/O to the file. The following types are defined:
-
- **sync**
- Basic :manpage:`read(2)` or :manpage:`write(2)`
- I/O. :manpage:`lseek(2)` is used to position the I/O location.
- See :option:`fsync` and :option:`fdatasync` for syncing write I/Os.
-
- **psync**
- Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O. Default on
- all supported operating systems except for Windows.
-
- **vsync**
- Basic :manpage:`readv(2)` or :manpage:`writev(2)` I/O. Will emulate
- queuing by coalescing adjacent I/Os into a single submission.
-
- **pvsync**
- Basic :manpage:`preadv(2)` or :manpage:`pwritev(2)` I/O.
-
- **pvsync2**
- Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O.
-
- **io_uring**
- Fast Linux native asynchronous I/O. Supports async IO
- for both direct and buffered IO.
- This engine defines engine specific options.
-
- **libaio**
- Linux native asynchronous I/O. Note that Linux may only support
- queued behavior with non-buffered I/O (set ``direct=1`` or
- ``buffered=0``).
- This engine defines engine specific options.
-
- **posixaio**
- POSIX asynchronous I/O using :manpage:`aio_read(3)` and
- :manpage:`aio_write(3)`.
-
- **solarisaio**
- Solaris native asynchronous I/O.
-
- **windowsaio**
- Windows native asynchronous I/O. Default on Windows.
-
- **mmap**
- File is memory mapped with :manpage:`mmap(2)` and data copied
- to/from using :manpage:`memcpy(3)`.
-
- **splice**
- :manpage:`splice(2)` is used to transfer the data and
- :manpage:`vmsplice(2)` to transfer data from user space to the
- kernel.
-
- **sg**
- SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
- ioctl, or if the target is an sg character device we use
- :manpage:`read(2)` and :manpage:`write(2)` for asynchronous
- I/O. Requires :option:`filename` option to specify either block or
- character devices. This engine supports trim operations.
- The sg engine includes engine specific options.
-
- **libzbc**
- Read, write, trim and ZBC/ZAC operations to a zoned
- block device using libzbc library. The target can be
- either an SG character device or a block device file.
-
- **null**
- Doesn't transfer any data, just pretends to. This is mainly used to
- exercise fio itself and for debugging/testing purposes.
-
- **net**
- Transfer over the network to given ``host:port``. Depending on the
- :option:`protocol` used, the :option:`hostname`, :option:`port`,
- :option:`listen` and :option:`filename` options are used to specify
- what sort of connection to make, while the :option:`protocol` option
- determines which protocol will be used. This engine defines engine
- specific options.
-
- **netsplice**
- Like **net**, but uses :manpage:`splice(2)` and
- :manpage:`vmsplice(2)` to map data and send/receive.
- This engine defines engine specific options.
-
- **cpuio**
- Doesn't transfer any data, but burns CPU cycles according to the
- :option:`cpuload`, :option:`cpuchunks` and :option:`cpumode` options.
- Setting :option:`cpuload`\=85 will cause that job to do nothing but burn 85%
- of the CPU. In case of SMP machines, use :option:`numjobs`\=<nr_of_cpu>
- to get desired CPU usage, as the cpuload only loads a
- single CPU at the desired rate. A job never finishes unless there is
- at least one non-cpuio job.
- Setting :option:`cpumode`\=qsort replace the default noop instructions loop
- by a qsort algorithm to consume more energy.
-
- **rdma**
- The RDMA I/O engine supports both RDMA memory semantics
- (RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
- InfiniBand, RoCE and iWARP protocols. This engine defines engine
- specific options.
-
- **falloc**
- I/O engine that does regular fallocate to simulate data transfer as
- fio ioengine.
-
- DDIR_READ
- does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
-
- DDIR_WRITE
- does fallocate(,mode = 0).
-
- DDIR_TRIM
- does fallocate(,mode = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
-
- **ftruncate**
- I/O engine that sends :manpage:`ftruncate(2)` operations in response
- to write (DDIR_WRITE) events. Each ftruncate issued sets the file's
- size to the current block offset. :option:`blocksize` is ignored.
-
- **e4defrag**
- I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
- defragment activity in request to DDIR_WRITE event.
-
- **rados**
- I/O engine supporting direct access to Ceph Reliable Autonomic
- Distributed Object Store (RADOS) via librados. This ioengine
- defines engine specific options.
-
- **rbd**
- I/O engine supporting direct access to Ceph Rados Block Devices
- (RBD) via librbd without the need to use the kernel rbd driver. This
- ioengine defines engine specific options.
-
- **http**
- I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to
- a WebDAV or S3 endpoint. This ioengine defines engine specific options.
-
- This engine only supports direct IO of iodepth=1; you need to scale this
- via numjobs. blocksize defines the size of the objects to be created.
-
- TRIM is translated to object deletion.
-
- **gfapi**
- Using GlusterFS libgfapi sync interface to direct access to
- GlusterFS volumes without having to go through FUSE. This ioengine
- defines engine specific options.
-
- **gfapi_async**
- Using GlusterFS libgfapi async interface to direct access to
- GlusterFS volumes without having to go through FUSE. This ioengine
- defines engine specific options.
-
- **libhdfs**
- Read and write through Hadoop (HDFS). The :option:`filename` option
- is used to specify host,port of the hdfs name-node to connect. This
- engine interprets offsets a little differently. In HDFS, files once
- created cannot be modified so random writes are not possible. To
- imitate this the libhdfs engine expects a bunch of small files to be
- created over HDFS and will randomly pick a file from them
- based on the offset generated by fio backend (see the example
- job file to create such files, use ``rw=write`` option). Please
- note, it may be necessary to set environment variables to work
- with HDFS/libhdfs properly. Each job uses its own connection to
- HDFS.
-
- **mtd**
- Read, write and erase an MTD character device (e.g.,
- :file:`/dev/mtd0`). Discards are treated as erases. Depending on the
- underlying device type, the I/O may have to go in a certain pattern,
- e.g., on NAND, writing sequentially to erase blocks and discarding
- before overwriting. The `trimwrite` mode works well for this
- constraint.
-
- **pmemblk**
- Read and write using filesystem DAX to a file on a filesystem
- mounted with DAX on a persistent memory device through the PMDK
- libpmemblk library.
-
- **dev-dax**
- Read and write using device DAX to a persistent memory device (e.g.,
- /dev/dax0.0) through the PMDK libpmem library.
-
- **external**
- Prefix to specify loading an external I/O engine object file. Append
- the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load
- ioengine :file:`foo.o` in :file:`/tmp`. The path can be either
- absolute or relative. See :file:`engines/skeleton_external.c` for
- details of writing an external I/O engine.
-
- **filecreate**
- Simply create the files and do no I/O to them. You still need to
- set `filesize` so that all the accounting still occurs, but no
- actual I/O will be done other than creating the file.
-
- **filestat**
- Simply do stat() and do no I/O to the file. You need to set 'filesize'
- and 'nrfiles', so that files will be created.
- This engine is to measure file lookup and meta data access.
-
- **filedelete**
- Simply delete the files by unlink() and do no I/O to them. You need to set 'filesize'
- and 'nrfiles', so that the files will be created.
- This engine is to measure file delete.
-
- **libpmem**
- Read and write using mmap I/O to a file on a filesystem
- mounted with DAX on a persistent memory device through the PMDK
- libpmem library.
-
- **ime_psync**
- Synchronous read and write using DDN's Infinite Memory Engine (IME).
- This engine is very basic and issues calls to IME whenever an IO is
- queued.
-
- **ime_psyncv**
- Synchronous read and write using DDN's Infinite Memory Engine (IME).
- This engine uses iovecs and will try to stack as much IOs as possible
- (if the IOs are "contiguous" and the IO depth is not exceeded)
- before issuing a call to IME.
-
- **ime_aio**
- Asynchronous read and write using DDN's Infinite Memory Engine (IME).
- This engine will try to stack as much IOs as possible by creating
- requests for IME. FIO will then decide when to commit these requests.
- **libiscsi**
- Read and write iscsi lun with libiscsi.
- **nbd**
- Read and write a Network Block Device (NBD).
-
- **libcufile**
- I/O engine supporting libcufile synchronous access to nvidia-fs and a
- GPUDirect Storage-supported filesystem. This engine performs
- I/O without transferring buffers between user-space and the kernel,
- unless :option:`verify` is set or :option:`cuda_io` is `posix`.
- :option:`iomem` must not be `cudamalloc`. This ioengine defines
- engine specific options.
- **dfs**
- I/O engine supporting asynchronous read and write operations to the
- DAOS File System (DFS) via libdfs.
-
- **nfs**
- I/O engine supporting asynchronous read and write operations to
- NFS filesystems from userspace via libnfs. This is useful for
- achieving higher concurrency and thus throughput than is possible
- via kernel NFS.
-
- **exec**
- Execute 3rd party tools. Could be used to perform monitoring during jobs runtime.
-
-I/O engine specific parameters
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-In addition, there are some parameters which are only valid when a specific
-:option:`ioengine` is in use. These are used identically to normal parameters,
-with the caveat that when used on the command line, they must come after the
-:option:`ioengine` that defines them is selected.
-
-.. option:: cmdprio_percentage=int[,int] : [io_uring] [libaio]
-
- Set the percentage of I/O that will be issued with the highest priority.
- Default: 0. A single value applies to reads and writes. Comma-separated
- values may be specified for reads and writes. For this option to be
- effective, NCQ priority must be supported and enabled, and `direct=1'
- option must be used. fio must also be run as the root user. Unlike
- slat/clat/lat stats, which can be tracked and reported independently, per
- priority stats only track and report a single type of latency. By default,
- completion latency (clat) will be reported, if :option:`lat_percentiles` is
- set, total latency (lat) will be reported.
-
-.. option:: cmdprio_class=int[,int] : [io_uring] [libaio]
-
- Set the I/O priority class to use for I/Os that must be issued with
- a priority when :option:`cmdprio_percentage` or
- :option:`cmdprio_bssplit` is set. If not specified when
- :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
- this defaults to the highest priority class. A single value applies
- to reads and writes. Comma-separated values may be specified for
- reads and writes. See :manpage:`ionice(1)`. See also the
- :option:`prioclass` option.
-
-.. option:: cmdprio=int[,int] : [io_uring] [libaio]
-
- Set the I/O priority value to use for I/Os that must be issued with
- a priority when :option:`cmdprio_percentage` or
- :option:`cmdprio_bssplit` is set. If not specified when
- :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
- this defaults to 0.
- Linux limits us to a positive value between 0 and 7, with 0 being the
- highest. A single value applies to reads and writes. Comma-separated
- values may be specified for reads and writes. See :manpage:`ionice(1)`.
- Refer to an appropriate manpage for other operating systems since
- meaning of priority may differ. See also the :option:`prio` option.
-
-.. option:: cmdprio_bssplit=str[,str] : [io_uring] [libaio]
- To get a finer control over I/O priority, this option allows
- specifying the percentage of IOs that must have a priority set
- depending on the block size of the IO. This option is useful only
- when used together with the :option:`bssplit` option, that is,
- multiple different block sizes are used for reads and writes.
-
- The first accepted format for this option is the same as the format of
- the :option:`bssplit` option:
-
- cmdprio_bssplit=blocksize/percentage:blocksize/percentage
-
- In this case, each entry will use the priority class and priority
- level defined by the options :option:`cmdprio_class` and
- :option:`cmdprio` respectively.
-
- The second accepted format for this option is:
-
- cmdprio_bssplit=blocksize/percentage/class/level:blocksize/percentage/class/level
-
- In this case, the priority class and priority level is defined inside
- each entry. In comparison with the first accepted format, the second
- accepted format does not restrict all entries to have the same priority
- class and priority level.
-
- For both formats, only the read and write data directions are supported,
- values for trim IOs are ignored. This option is mutually exclusive with
- the :option:`cmdprio_percentage` option.
-
-.. option:: fixedbufs : [io_uring]
-
- If fio is asked to do direct IO, then Linux will map pages for each
- IO call, and release them when IO is done. If this option is set, the
- pages are pre-mapped before IO is started. This eliminates the need to
- map and release for each IO. This is more efficient, and reduces the
- IO latency as well.
-
-.. option:: hipri : [io_uring]
-
- If this option is set, fio will attempt to use polled IO completions.
- Normal IO completions generate interrupts to signal the completion of
- IO, polled completions do not. Hence they are require active reaping
- by the application. The benefits are more efficient IO for high IOPS
- scenarios, and lower latencies for low queue depth IO.
-
-.. option:: registerfiles : [io_uring]
-
- With this option, fio registers the set of files being used with the
- kernel. This avoids the overhead of managing file counts in the kernel,
- making the submission and completion part more lightweight. Required
- for the below :option:`sqthread_poll` option.
-
-.. option:: sqthread_poll : [io_uring]
-
- Normally fio will submit IO by issuing a system call to notify the
- kernel of available items in the SQ ring. If this option is set, the
- act of submitting IO will be done by a polling thread in the kernel.
- This frees up cycles for fio, at the cost of using more CPU in the
- system.
-
-.. option:: sqthread_poll_cpu : [io_uring]
-
- When :option:`sqthread_poll` is set, this option provides a way to
- define which CPU should be used for the polling thread.
-
-.. option:: userspace_reap : [libaio]
-
- Normally, with the libaio engine in use, fio will use the
- :manpage:`io_getevents(2)` system call to reap newly returned events. With
- this flag turned on, the AIO ring will be read directly from user-space to
- reap events. The reaping mode is only enabled when polling for a minimum of
- 0 events (e.g. when :option:`iodepth_batch_complete` `=0`).
-
-.. option:: hipri : [pvsync2]
-
- Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority
- than normal.
-
-.. option:: hipri_percentage : [pvsync2]
-
- When hipri is set this determines the probability of a pvsync2 I/O being high
- priority. The default is 100%.
-
-.. option:: nowait : [pvsync2] [libaio] [io_uring]
-
- By default if a request cannot be executed immediately (e.g. resource starvation,
- waiting on locks) it is queued and the initiating process will be blocked until
- the required resource becomes free.
-
- This option sets the RWF_NOWAIT flag (supported from the 4.14 Linux kernel) and
- the call will return instantly with EAGAIN or a partial result rather than waiting.
-
- It is useful to also use ignore_error=EAGAIN when using this option.
-
- Note: glibc 2.27, 2.28 have a bug in syscall wrappers preadv2, pwritev2.
- They return EOPNOTSUP instead of EAGAIN.
-
- For cached I/O, using this option usually means a request operates only with
- cached data. Currently the RWF_NOWAIT flag does not supported for cached write.
-
- For direct I/O, requests will only succeed if cache invalidation isn't required,
- file blocks are fully allocated and the disk request could be issued immediately.
-
-.. option:: cpuload=int : [cpuio]
-
- Attempt to use the specified percentage of CPU cycles. This is a mandatory
- option when using cpuio I/O engine.
-
-.. option:: cpuchunks=int : [cpuio]
-
- Split the load into cycles of the given time. In microseconds.
-
-.. option:: cpumode=str : [cpuio]
-
- Specify how to stress the CPU. It can take these two values:
-
- **noop**
- This is the default where the CPU executes noop instructions.
- **qsort**
- Replace the default noop instructions loop with a qsort algorithm to
- consume more energy.
-
-.. option:: exit_on_io_done=bool : [cpuio]
-
- Detect when I/O threads are done, then exit.
-
-.. option:: namenode=str : [libhdfs]
-
- The hostname or IP address of a HDFS cluster namenode to contact.
-
-.. option:: port=int
-
- [libhdfs]
-
- The listening port of the HFDS cluster namenode.
-
- [netsplice], [net]
-
- The TCP or UDP port to bind to or connect to. If this is used with
- :option:`numjobs` to spawn multiple instances of the same job type, then
- this will be the starting port number since fio will use a range of
- ports.
-
- [rdma], [librpma_*]
-
- The port to use for RDMA-CM communication. This should be the same value
- on the client and the server side.
-
-.. option:: hostname=str : [netsplice] [net] [rdma]
-
- The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If the job
- is a TCP listener or UDP reader, the hostname is not used and must be omitted
- unless it is a valid UDP multicast address.
-
-.. option:: serverip=str : [librpma_*]
-
- The IP address to be used for RDMA-CM based I/O.
-
-.. option:: direct_write_to_pmem=bool : [librpma_*]
-
- Set to 1 only when Direct Write to PMem from the remote host is possible.
- Otherwise, set to 0.
-
-.. option:: busy_wait_polling=bool : [librpma_*_server]
-
- Set to 0 to wait for completion instead of busy-wait polling completion.
- Default: 1.
-
-.. option:: interface=str : [netsplice] [net]
-
- The IP address of the network interface used to send or receive UDP
- multicast.
-
-.. option:: ttl=int : [netsplice] [net]
-
- Time-to-live value for outgoing UDP multicast packets. Default: 1.
-
-.. option:: nodelay=bool : [netsplice] [net]
-
- Set TCP_NODELAY on TCP connections.
-
-.. option:: protocol=str, proto=str : [netsplice] [net]
-
- The network protocol to use. Accepted values are:
-
- **tcp**
- Transmission control protocol.
- **tcpv6**
- Transmission control protocol V6.
- **udp**
- User datagram protocol.
- **udpv6**
- User datagram protocol V6.
- **unix**
- UNIX domain socket.
-
- When the protocol is TCP or UDP, the port must also be given, as well as the
- hostname if the job is a TCP listener or UDP reader. For unix sockets, the
- normal :option:`filename` option should be used and the port is invalid.
-
-.. option:: listen : [netsplice] [net]
-
- For TCP network connections, tell fio to listen for incoming connections
- rather than initiating an outgoing connection. The :option:`hostname` must
- be omitted if this option is used.
-
-.. option:: pingpong : [netsplice] [net]
-
- Normally a network writer will just continue writing data, and a network
- reader will just consume packages. If ``pingpong=1`` is set, a writer will
- send its normal payload to the reader, then wait for the reader to send the
- same payload back. This allows fio to measure network latencies. The
- submission and completion latencies then measure local time spent sending or
- receiving, and the completion latency measures how long it took for the
- other end to receive and send back. For UDP multicast traffic
- ``pingpong=1`` should only be set for a single reader when multiple readers
- are listening to the same address.
-
-.. option:: window_size : [netsplice] [net]
-
- Set the desired socket buffer size for the connection.
-
-.. option:: mss : [netsplice] [net]
-
- Set the TCP maximum segment size (TCP_MAXSEG).
-
-.. option:: donorname=str : [e4defrag]
-
- File will be used as a block donor (swap extents between files).
-
-.. option:: inplace=int : [e4defrag]
-
- Configure donor file blocks allocation strategy:
-
- **0**
- Default. Preallocate donor's file on init.
- **1**
- Allocate space immediately inside defragment event, and free right
- after event.
-
-.. option:: clustername=str : [rbd,rados]
-
- Specifies the name of the Ceph cluster.
-
-.. option:: rbdname=str : [rbd]
-
- Specifies the name of the RBD.
-
-.. option:: pool=str : [rbd,rados]
-
- Specifies the name of the Ceph pool containing RBD or RADOS data.
-
-.. option:: clientname=str : [rbd,rados]
-
- Specifies the username (without the 'client.' prefix) used to access the
- Ceph cluster. If the *clustername* is specified, the *clientname* shall be
- the full *type.id* string. If no type. prefix is given, fio will add
- 'client.' by default.
-
-.. option:: busy_poll=bool : [rbd,rados]
-
- Poll store instead of waiting for completion. Usually this provides better
- throughput at cost of higher(up to 100%) CPU utilization.
-
-.. option:: touch_objects=bool : [rados]
-
- During initialization, touch (create if do not exist) all objects (files).
- Touching all objects affects ceph caches and likely impacts test results.
- Enabled by default.
-
-.. option:: skip_bad=bool : [mtd]
-
- Skip operations against known bad blocks.
-
-.. option:: hdfsdirectory : [libhdfs]
-
- libhdfs will create chunk in this HDFS directory.
-
-.. option:: chunk_size : [libhdfs]
-
- The size of the chunk to use for each file.
-
-.. option:: verb=str : [rdma]
-
- The RDMA verb to use on this side of the RDMA ioengine connection. Valid
- values are write, read, send and recv. These correspond to the equivalent
- RDMA verbs (e.g. write = rdma_write etc.). Note that this only needs to be
- specified on the client side of the connection. See the examples folder.
-
-.. option:: bindname=str : [rdma]
-
- The name to use to bind the local RDMA-CM connection to a local RDMA device.
- This could be a hostname or an IPv4 or IPv6 address. On the server side this
- will be passed into the rdma_bind_addr() function and on the client site it
- will be used in the rdma_resolve_add() function. This can be useful when
- multiple paths exist between the client and the server or in certain loopback
- configurations.
-
-.. option:: stat_type=str : [filestat]
-
- Specify stat system call type to measure lookup/getattr performance.
- Default is **stat** for :manpage:`stat(2)`.
-
-.. option:: readfua=bool : [sg]
-
- With readfua option set to 1, read operations include
- the force unit access (fua) flag. Default is 0.
-
-.. option:: writefua=bool : [sg]
-
- With writefua option set to 1, write operations include
- the force unit access (fua) flag. Default is 0.
-
-.. option:: sg_write_mode=str : [sg]
-
- Specify the type of write commands to issue. This option can take three values:
-
- **write**
- This is the default where write opcodes are issued as usual.
- **write_and_verify**
- Issue WRITE AND VERIFY commands. The BYTCHK bit is set to 0. This
- directs the device to carry out a medium verification with no data
- comparison. The writefua option is ignored with this selection.
- **verify**
- This option is deprecated. Use write_and_verify instead.
- **write_same**
- Issue WRITE SAME commands. This transfers a single block to the device
- and writes this same block of data to a contiguous sequence of LBAs
- beginning at the specified offset. fio's block size parameter specifies
- the amount of data written with each command. However, the amount of data
- actually transferred to the device is equal to the device's block
- (sector) size. For a device with 512 byte sectors, blocksize=8k will
- write 16 sectors with each command. fio will still generate 8k of data
- for each command but only the first 512 bytes will be used and
- transferred to the device. The writefua option is ignored with this
- selection.
- **same**
- This option is deprecated. Use write_same instead.
- **write_same_ndob**
- Issue WRITE SAME(16) commands as above but with the No Data Output
- Buffer (NDOB) bit set. No data will be transferred to the device with
- this bit set. Data written will be a pre-determined pattern such as
- all zeroes.
- **write_stream**
- Issue WRITE STREAM(16) commands. Use the **stream_id** option to specify
- the stream identifier.
- **verify_bytchk_00**
- Issue VERIFY commands with BYTCHK set to 00. This directs the
- device to carry out a medium verification with no data comparison.
- **verify_bytchk_01**
- Issue VERIFY commands with BYTCHK set to 01. This directs the device to
- compare the data on the device with the data transferred to the device.
- **verify_bytchk_11**
- Issue VERIFY commands with BYTCHK set to 11. This transfers a
- single block to the device and compares the contents of this block with the
- data on the device beginning at the specified offset. fio's block size
- parameter specifies the total amount of data compared with this command.
- However, only one block (sector) worth of data is transferred to the device.
- This is similar to the WRITE SAME command except that data is compared instead
- of written.
-
-.. option:: stream_id=int : [sg]
-
- Set the stream identifier for WRITE STREAM commands. If this is set to 0 (which is not
- a valid stream identifier) fio will open a stream and then close it when done. Default
- is 0.
-
-.. option:: hipri : [sg]
-
- If this option is set, fio will attempt to use polled IO completions.
- This will have a similar effect as (io_uring)hipri. Only SCSI READ and
- WRITE commands will have the SGV4_FLAG_HIPRI set (not UNMAP (trim) nor
- VERIFY). Older versions of the Linux sg driver that do not support
- hipri will simply ignore this flag and do normal IO. The Linux SCSI
- Low Level Driver (LLD) that "owns" the device also needs to support
- hipri (also known as iopoll and mq_poll). The MegaRAID driver is an
- example of a SCSI LLD. Default: clear (0) which does normal
- (interrupted based) IO.
-
-.. option:: http_host=str : [http]
-
- Hostname to connect to. For S3, this could be the bucket hostname.
- Default is **localhost**
-
-.. option:: http_user=str : [http]
-
- Username for HTTP authentication.
-
-.. option:: http_pass=str : [http]
-
- Password for HTTP authentication.
-
-.. option:: https=str : [http]
-
- Enable HTTPS instead of http. *on* enables HTTPS; *insecure*
- will enable HTTPS, but disable SSL peer verification (use with
- caution!). Default is **off**
-
-.. option:: http_mode=str : [http]
-
- Which HTTP access mode to use: *webdav*, *swift*, or *s3*.
- Default is **webdav**
-
-.. option:: http_s3_region=str : [http]
-
- The S3 region/zone string.
- Default is **us-east-1**
-
-.. option:: http_s3_key=str : [http]
-
- The S3 secret key.
-
-.. option:: http_s3_keyid=str : [http]
-
- The S3 key/access id.
-
-.. option:: http_swift_auth_token=str : [http]
-
- The Swift auth token. See the example configuration file on how
- to retrieve this.
-
-.. option:: http_verbose=int : [http]
-
- Enable verbose requests from libcurl. Useful for debugging. 1
- turns on verbose logging from libcurl, 2 additionally enables
- HTTP IO tracing. Default is **0**
-
-.. option:: uri=str : [nbd]
-
- Specify the NBD URI of the server to test. The string
- is a standard NBD URI
- (see https://github.com/NetworkBlockDevice/nbd/tree/master/doc).
- Example URIs: nbd://localhost:10809
- nbd+unix:///?socket=/tmp/socket
- nbds://tlshost/exportname
-
-.. option:: gpu_dev_ids=str : [libcufile]
-
- Specify the GPU IDs to use with CUDA. This is a colon-separated list of
- int. GPUs are assigned to workers roundrobin. Default is 0.
-
-.. option:: cuda_io=str : [libcufile]
-
- Specify the type of I/O to use with CUDA. Default is **cufile**.
-
- **cufile**
- Use libcufile and nvidia-fs. This option performs I/O directly
- between a GPUDirect Storage filesystem and GPU buffers,
- avoiding use of a bounce buffer. If :option:`verify` is set,
- cudaMemcpy is used to copy verificaton data between RAM and GPU.
- Verification data is copied from RAM to GPU before a write
- and from GPU to RAM after a read. :option:`direct` must be 1.
- **posix**
- Use POSIX to perform I/O with a RAM buffer, and use cudaMemcpy
- to transfer data between RAM and the GPUs. Data is copied from
- GPU to RAM before a write and copied from RAM to GPU after a
- read. :option:`verify` does not affect use of cudaMemcpy.
-
-.. option:: pool=str : [dfs]
-
- Specify the label or UUID of the DAOS pool to connect to.
-
-.. option:: cont=str : [dfs]
-
- Specify the label or UUID of the DAOS container to open.
-
-.. option:: chunk_size=int : [dfs]
-
- Specificy a different chunk size (in bytes) for the dfs file.
- Use DAOS container's chunk size by default.
-
-.. option:: object_class=str : [dfs]
-
- Specificy a different object class for the dfs file.
- Use DAOS container's object class by default.
-
-.. option:: nfs_url=str : [nfs]
-
- URL in libnfs format, eg nfs://<server|ipv4|ipv6>/path[?arg=val[&arg=val]*]
- Refer to the libnfs README for more details.
-
-.. option:: program=str : [exec]
-
- Specify the program to execute.
-
-.. option:: arguments=str : [exec]
-
- Specify arguments to pass to program.
- Some special variables can be expanded to pass fio's job details to the program.
-
- **%r**
- Replaced by the duration of the job in seconds.
- **%n**
- Replaced by the name of the job.
-
-.. option:: grace_time=int : [exec]
-
- Specify the time between the SIGTERM and SIGKILL signals. Default is 1 second.
-
-.. option:: std_redirect=bool : [exec]
-
- If set, stdout and stderr streams are redirected to files named from the job name. Default is true.
-
-I/O depth
-~~~~~~~~~
-
-.. option:: iodepth=int
-
- Number of I/O units to keep in flight against the file. Note that
- increasing *iodepth* beyond 1 will not affect synchronous ioengines (except
- for small degrees when :option:`verify_async` is in use). Even async
- engines may impose OS restrictions causing the desired depth not to be
- achieved. This may happen on Linux when using libaio and not setting
- :option:`direct`\=1, since buffered I/O is not async on that OS. Keep an
- eye on the I/O depth distribution in the fio output to verify that the
- achieved depth is as expected. Default: 1.
-
-.. option:: iodepth_batch_submit=int, iodepth_batch=int
-
- This defines how many pieces of I/O to submit at once. It defaults to 1
- which means that we submit each I/O as soon as it is available, but can be
- raised to submit bigger batches of I/O at the time. If it is set to 0 the
- :option:`iodepth` value will be used.
-
-.. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int
-
- This defines how many pieces of I/O to retrieve at once. It defaults to 1
- which means that we'll ask for a minimum of 1 I/O in the retrieval process
- from the kernel. The I/O retrieval will go on until we hit the limit set by
- :option:`iodepth_low`. If this variable is set to 0, then fio will always
- check for completed events before queuing more I/O. This helps reduce I/O
- latency, at the cost of more retrieval system calls.
-
-.. option:: iodepth_batch_complete_max=int
-
- This defines maximum pieces of I/O to retrieve at once. This variable should
- be used along with :option:`iodepth_batch_complete_min`\=int variable,
- specifying the range of min and max amount of I/O which should be
- retrieved. By default it is equal to the :option:`iodepth_batch_complete_min`
- value.
-
- Example #1::
-
- iodepth_batch_complete_min=1
- iodepth_batch_complete_max=<iodepth>
-
- which means that we will retrieve at least 1 I/O and up to the whole
- submitted queue depth. If none of I/O has been completed yet, we will wait.
-
- Example #2::
-
- iodepth_batch_complete_min=0
- iodepth_batch_complete_max=<iodepth>
-
- which means that we can retrieve up to the whole submitted queue depth, but
- if none of I/O has been completed yet, we will NOT wait and immediately exit
- the system call. In this example we simply do polling.
-
-.. option:: iodepth_low=int
-
- The low water mark indicating when to start filling the queue
- again. Defaults to the same as :option:`iodepth`, meaning that fio will
- attempt to keep the queue full at all times. If :option:`iodepth` is set to
- e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of
- 16 requests, it will let the depth drain down to 4 before starting to fill
- it again.
-
-.. option:: serialize_overlap=bool
-
- Serialize in-flight I/Os that might otherwise cause or suffer from data races.
- When two or more I/Os are submitted simultaneously, there is no guarantee that
- the I/Os will be processed or completed in the submitted order. Further, if
- two or more of those I/Os are writes, any overlapping region between them can
- become indeterminate/undefined on certain storage. These issues can cause
- verification to fail erratically when at least one of the racing I/Os is
- changing data and the overlapping region has a non-zero size. Setting
- ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
- serializing in-flight I/Os that have a non-zero overlap. Note that setting
- this option can reduce both performance and the :option:`iodepth` achieved.
-
- This option only applies to I/Os issued for a single job except when it is
- enabled along with :option:`io_submit_mode`\=offload. In offload mode, fio
- will check for overlap among all I/Os submitted by offload jobs with :option:`serialize_overlap`
- enabled.
-
- Default: false.
-
-.. option:: io_submit_mode=str
-
- This option controls how fio submits the I/O to the I/O engine. The default
- is `inline`, which means that the fio job threads submit and reap I/O
- directly. If set to `offload`, the job threads will offload I/O submission
- to a dedicated pool of I/O threads. This requires some coordination and thus
- has a bit of extra overhead, especially for lower queue depth I/O where it
- can increase latencies. The benefit is that fio can manage submission rates
- independently of the device completion rates. This avoids skewed latency
- reporting if I/O gets backed up on the device side (the coordinated omission
- problem). Note that this option cannot reliably be used with async IO
- engines.
-
-
-I/O rate
-~~~~~~~~
-
-.. option:: thinktime=time
-
- Stall the job for the specified period of time after an I/O has completed before issuing the
- next. May be used to simulate processing being done by an application.
- When the unit is omitted, the value is interpreted in microseconds. See
- :option:`thinktime_blocks`, :option:`thinktime_iotime` and :option:`thinktime_spin`.
-
-.. option:: thinktime_spin=time
-
- Only valid if :option:`thinktime` is set - pretend to spend CPU time doing
- something with the data received, before falling back to sleeping for the
- rest of the period specified by :option:`thinktime`. When the unit is
- omitted, the value is interpreted in microseconds.
-
-.. option:: thinktime_blocks=int
-
- Only valid if :option:`thinktime` is set - control how many blocks to issue,
- before waiting :option:`thinktime` usecs. If not set, defaults to 1 which will make
- fio wait :option:`thinktime` usecs after every block. This effectively makes any
- queue depth setting redundant, since no more than 1 I/O will be queued
- before we have to complete it and do our :option:`thinktime`. In other words, this
- setting effectively caps the queue depth if the latter is larger.
-
-.. option:: thinktime_blocks_type=str
-
- Only valid if :option:`thinktime` is set - control how :option:`thinktime_blocks`
- triggers. The default is `complete`, which triggers thinktime when fio completes
- :option:`thinktime_blocks` blocks. If this is set to `issue`, then the trigger happens
- at the issue side.
-
-.. option:: thinktime_iotime=time
-
- Only valid if :option:`thinktime` is set - control :option:`thinktime`
- interval by time. The :option:`thinktime` stall is repeated after IOs
- are executed for :option:`thinktime_iotime`. For example,
- ``--thinktime_iotime=9s --thinktime=1s`` repeat 10-second cycle with IOs
- for 9 seconds and stall for 1 second. When the unit is omitted,
- :option:`thinktime_iotime` is interpreted as a number of seconds. If
- this option is used together with :option:`thinktime_blocks`, the
- :option:`thinktime` stall is repeated after :option:`thinktime_iotime`
- or after :option:`thinktime_blocks` IOs, whichever happens first.
-
-.. option:: rate=int[,int][,int]
-
- Cap the bandwidth used by this job. The number is in bytes/sec, the normal
- suffix rules apply. Comma-separated values may be specified for reads,
- writes, and trims as described in :option:`blocksize`.
-
- For example, using `rate=1m,500k` would limit reads to 1MiB/sec and writes to
- 500KiB/sec. Capping only reads or writes can be done with `rate=,500k` or
- `rate=500k,` where the former will only limit writes (to 500KiB/sec) and the
- latter will only limit reads.
-
-.. option:: rate_min=int[,int][,int]
-
- Tell fio to do whatever it can to maintain at least this bandwidth. Failing
- to meet this requirement will cause the job to exit. Comma-separated values
- may be specified for reads, writes, and trims as described in
- :option:`blocksize`.
-
-.. option:: rate_iops=int[,int][,int]
-
- Cap the bandwidth to this number of IOPS. Basically the same as
- :option:`rate`, just specified independently of bandwidth. If the job is
- given a block size range instead of a fixed value, the smallest block size
- is used as the metric. Comma-separated values may be specified for reads,
- writes, and trims as described in :option:`blocksize`.
-
-.. option:: rate_iops_min=int[,int][,int]
-
- If fio doesn't meet this rate of I/O, it will cause the job to exit.
- Comma-separated values may be specified for reads, writes, and trims as
- described in :option:`blocksize`.
-
-.. option:: rate_process=str
-
- This option controls how fio manages rated I/O submissions. The default is
- `linear`, which submits I/O in a linear fashion with fixed delays between
- I/Os that gets adjusted based on I/O completion rates. If this is set to
- `poisson`, fio will submit I/O based on a more real world random request
- flow, known as the Poisson process
- (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be
- 10^6 / IOPS for the given workload.
-
-.. option:: rate_ignore_thinktime=bool
-
- By default, fio will attempt to catch up to the specified rate setting,
- if any kind of thinktime setting was used. If this option is set, then
- fio will ignore the thinktime and continue doing IO at the specified
- rate, instead of entering a catch-up mode after thinktime is done.
-
-
-I/O latency
-~~~~~~~~~~~
-
-.. option:: latency_target=time
-
- If set, fio will attempt to find the max performance point that the given
- workload will run at while maintaining a latency below this target. When
- the unit is omitted, the value is interpreted in microseconds. See
- :option:`latency_window` and :option:`latency_percentile`.
-
-.. option:: latency_window=time
-
- Used with :option:`latency_target` to specify the sample window that the job
- is run at varying queue depths to test the performance. When the unit is
- omitted, the value is interpreted in microseconds.
-
-.. option:: latency_percentile=float
-
- The percentage of I/Os that must fall within the criteria specified by
- :option:`latency_target` and :option:`latency_window`. If not set, this
- defaults to 100.0, meaning that all I/Os must be equal or below to the value
- set by :option:`latency_target`.
-
-.. option:: latency_run=bool
-
- Used with :option:`latency_target`. If false (default), fio will find
- the highest queue depth that meets :option:`latency_target` and exit. If
- true, fio will continue running and try to meet :option:`latency_target`
- by adjusting queue depth.
-
-.. option:: max_latency=time[,time][,time]
-
- If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
- maximum latency. When the unit is omitted, the value is interpreted in
- microseconds. Comma-separated values may be specified for reads, writes,
- and trims as described in :option:`blocksize`.
-
-.. option:: rate_cycle=int
-
- Average bandwidth for :option:`rate` and :option:`rate_min` over this number
- of milliseconds. Defaults to 1000.
-
-
-I/O replay
-~~~~~~~~~~
-
-.. option:: write_iolog=str
-
- Write the issued I/O patterns to the specified file. See
- :option:`read_iolog`. Specify a separate file for each job, otherwise the
- iologs will be interspersed and the file may be corrupt.
-
-.. option:: read_iolog=str
-
- Open an iolog with the specified filename and replay the I/O patterns it
- contains. This can be used to store a workload and replay it sometime
- later. The iolog given may also be a blktrace binary file, which allows fio
- to replay a workload captured by :command:`blktrace`. See
- :manpage:`blktrace(8)` for how to capture such logging data. For blktrace
- replay, the file needs to be turned into a blkparse binary data file first
- (``blkparse <device> -o /dev/null -d file_for_fio.bin``).
- You can specify a number of files by separating the names with a ':'
- character. See the :option:`filename` option for information on how to
- escape ':' characters within the file names. These files will
- be sequentially assigned to job clones created by :option:`numjobs`.
- '-' is a reserved name, meaning read from stdin, notably if
- :option:`filename` is set to '-' which means stdin as well, then
- this flag can't be set to '-'.
-
-.. option:: read_iolog_chunked=bool
-
- Determines how iolog is read. If false(default) entire :option:`read_iolog`
- will be read at once. If selected true, input from iolog will be read
- gradually. Useful when iolog is very large, or it is generated.
-
-.. option:: merge_blktrace_file=str
-
- When specified, rather than replaying the logs passed to :option:`read_iolog`,
- the logs go through a merge phase which aggregates them into a single
- blktrace. The resulting file is then passed on as the :option:`read_iolog`
- parameter. The intention here is to make the order of events consistent.
- This limits the influence of the scheduler compared to replaying multiple
- blktraces via concurrent jobs.
-
-.. option:: merge_blktrace_scalars=float_list
-
- This is a percentage based option that is index paired with the list of
- files passed to :option:`read_iolog`. When merging is performed, scale
- the time of each event by the corresponding amount. For example,
- ``--merge_blktrace_scalars="50:100"`` runs the first trace in halftime
- and the second trace in realtime. This knob is separately tunable from
- :option:`replay_time_scale` which scales the trace during runtime and
- does not change the output of the merge unlike this option.
-
-.. option:: merge_blktrace_iters=float_list
-
- This is a whole number option that is index paired with the list of files
- passed to :option:`read_iolog`. When merging is performed, run each trace
- for the specified number of iterations. For example,
- ``--merge_blktrace_iters="2:1"`` runs the first trace for two iterations
- and the second trace for one iteration.
-
-.. option:: replay_no_stall=bool
-
- When replaying I/O with :option:`read_iolog` the default behavior is to
- attempt to respect the timestamps within the log and replay them with the
- appropriate delay between IOPS. By setting this variable fio will not
- respect the timestamps and attempt to replay them as fast as possible while
- still respecting ordering. The result is the same I/O pattern to a given
- device, but different timings.
-
-.. option:: replay_time_scale=int
-
- When replaying I/O with :option:`read_iolog`, fio will honor the
- original timing in the trace. With this option, it's possible to scale
- the time. It's a percentage option, if set to 50 it means run at 50%
- the original IO rate in the trace. If set to 200, run at twice the
- original IO rate. Defaults to 100.
-
-.. option:: replay_redirect=str
-
- While replaying I/O patterns using :option:`read_iolog` the default behavior
- is to replay the IOPS onto the major/minor device that each IOP was recorded
- from. This is sometimes undesirable because on a different machine those
- major/minor numbers can map to a different device. Changing hardware on the
- same system can also result in a different major/minor mapping.
- ``replay_redirect`` causes all I/Os to be replayed onto the single specified
- device regardless of the device it was recorded
- from. i.e. :option:`replay_redirect`\= :file:`/dev/sdc` would cause all I/O
- in the blktrace or iolog to be replayed onto :file:`/dev/sdc`. This means
- multiple devices will be replayed onto a single device, if the trace
- contains multiple devices. If you want multiple devices to be replayed
- concurrently to multiple redirected devices you must blkparse your trace
- into separate traces and replay them with independent fio invocations.
- Unfortunately this also breaks the strict time ordering between multiple
- device accesses.
-
-.. option:: replay_align=int
-
- Force alignment of the byte offsets in a trace to this value. The value
- must be a power of 2.
-
-.. option:: replay_scale=int
-
- Scale byte offsets down by this factor when replaying traces. Should most
- likely use :option:`replay_align` as well.
-
-.. option:: replay_skip=str
-
- Sometimes it's useful to skip certain IO types in a replay trace.
- This could be, for instance, eliminating the writes in the trace.
- Or not replaying the trims/discards, if you are redirecting to
- a device that doesn't support them. This option takes a comma
- separated list of read, write, trim, sync.
-
-
-Threads, processes and job synchronization
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. option:: thread
-
- Fio defaults to creating jobs by using fork, however if this option is
- given, fio will create jobs by using POSIX Threads' function
- :manpage:`pthread_create(3)` to create threads instead.
-
-.. option:: wait_for=str
-
- If set, the current job won't be started until all workers of the specified
- waitee job are done.
-
- ``wait_for`` operates on the job name basis, so there are a few
- limitations. First, the waitee must be defined prior to the waiter job
- (meaning no forward references). Second, if a job is being referenced as a
- waitee, it must have a unique name (no duplicate waitees).
-
-.. option:: nice=int
-
- Run the job with the given nice value. See man :manpage:`nice(2)`.
-
- On Windows, values less than -15 set the process class to "High"; -1 through
- -15 set "Above Normal"; 1 through 15 "Below Normal"; and above 15 "Idle"
- priority class.
-
-.. option:: prio=int
-
- Set the I/O priority value of this job. Linux limits us to a positive value
- between 0 and 7, with 0 being the highest. See man
- :manpage:`ionice(1)`. Refer to an appropriate manpage for other operating
- systems since meaning of priority may differ. For per-command priority
- setting, see I/O engine specific :option:`cmdprio_percentage` and
- :option:`cmdprio` options.
-
-.. option:: prioclass=int
-
- Set the I/O priority class. See man :manpage:`ionice(1)`. For per-command
- priority setting, see I/O engine specific :option:`cmdprio_percentage`
- and :option:`cmdprio_class` options.
-
-.. option:: cpus_allowed=str
-
- Controls the same options as :option:`cpumask`, but accepts a textual
- specification of the permitted CPUs instead and CPUs are indexed from 0. So
- to use CPUs 0 and 5 you would specify ``cpus_allowed=0,5``. This option also
- allows a range of CPUs to be specified -- say you wanted a binding to CPUs
- 0, 5, and 8 to 15, you would set ``cpus_allowed=0,5,8-15``.
-
- On Windows, when ``cpus_allowed`` is unset only CPUs from fio's current
- processor group will be used and affinity settings are inherited from the
- system. An fio build configured to target Windows 7 makes options that set
- CPUs processor group aware and values will set both the processor group
- and a CPU from within that group. For example, on a system where processor
- group 0 has 40 CPUs and processor group 1 has 32 CPUs, ``cpus_allowed``
- values between 0 and 39 will bind CPUs from processor group 0 and
- ``cpus_allowed`` values between 40 and 71 will bind CPUs from processor
- group 1. When using ``cpus_allowed_policy=shared`` all CPUs specified by a
- single ``cpus_allowed`` option must be from the same processor group. For
- Windows fio builds not built for Windows 7, CPUs will only be selected from
- (and be relative to) whatever processor group fio happens to be running in
- and CPUs from other processor groups cannot be used.
-
-.. option:: cpus_allowed_policy=str
-
- Set the policy of how fio distributes the CPUs specified by
- :option:`cpus_allowed` or :option:`cpumask`. Two policies are supported:
-
- **shared**
- All jobs will share the CPU set specified.
- **split**
- Each job will get a unique CPU from the CPU set.
-
- **shared** is the default behavior, if the option isn't specified. If
- **split** is specified, then fio will assign one cpu per job. If not
- enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
- in the set.
-
-.. option:: cpumask=int
-
- Set the CPU affinity of this job. The parameter given is a bit mask of
- allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
- and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
- :manpage:`sched_setaffinity(2)`. This may not work on all supported
- operating systems or kernel versions. This option doesn't work well for a
- higher CPU count than what you can store in an integer mask, so it can only
- control cpus 1-32. For boxes with larger CPU counts, use
- :option:`cpus_allowed`.
-
-.. option:: numa_cpu_nodes=str
-
- Set this job running on specified NUMA nodes' CPUs. The arguments allow
- comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable
- NUMA options support, fio must be built on a system with libnuma-dev(el)
- installed.
-
-.. option:: numa_mem_policy=str
-
- Set this job's memory policy and corresponding NUMA nodes. Format of the
- arguments::
-
- <mode>[:<nodelist>]
-
- ``mode`` is one of the following memory policies: ``default``, ``prefer``,
- ``bind``, ``interleave`` or ``local``. For ``default`` and ``local`` memory
- policies, no node needs to be specified. For ``prefer``, only one node is
- allowed. For ``bind`` and ``interleave`` the ``nodelist`` may be as
- follows: a comma delimited list of numbers, A-B ranges, or `all`.
-
-.. option:: cgroup=str
-
- Add job to this control group. If it doesn't exist, it will be created. The
- system must have a mounted cgroup blkio mount point for this to work. If
- your system doesn't have it mounted, you can do so with::
-
- # mount -t cgroup -o blkio none /cgroup
-
-.. option:: cgroup_weight=int
-
- Set the weight of the cgroup to this value. See the documentation that comes
- with the kernel, allowed values are in the range of 100..1000.
-
-.. option:: cgroup_nodelete=bool
-
- Normally fio will delete the cgroups it has created after the job
- completion. To override this behavior and to leave cgroups around after the
- job completion, set ``cgroup_nodelete=1``. This can be useful if one wants
- to inspect various cgroup files after job completion. Default: false.
-
-.. option:: flow_id=int
-
- The ID of the flow. If not specified, it defaults to being a global
- flow. See :option:`flow`.
-
-.. option:: flow=int
-
- Weight in token-based flow control. If this value is used, then there is a
- 'flow counter' which is used to regulate the proportion of activity between
- two or more jobs. Fio attempts to keep this flow counter near zero. The
- ``flow`` parameter stands for how much should be added or subtracted to the
- flow counter on each iteration of the main I/O loop. That is, if one job has
- ``flow=8`` and another job has ``flow=-1``, then there will be a roughly 1:8
- ratio in how much one runs vs the other.
-
-.. option:: flow_sleep=int
-
- The period of time, in microseconds, to wait after the flow counter
- has exceeded its proportion before retrying operations.
-
-.. option:: stonewall, wait_for_previous
-
- Wait for preceding jobs in the job file to exit, before starting this
- one. Can be used to insert serialization points in the job file. A stone
- wall also implies starting a new reporting group, see
- :option:`group_reporting`.
-
-.. option:: exitall
-
- By default, fio will continue running all other jobs when one job finishes.
- Sometimes this is not the desired action. Setting ``exitall`` will instead
- make fio terminate all jobs in the same group, as soon as one job of that
- group finishes.
-
-.. option:: exit_what
-
- By default, fio will continue running all other jobs when one job finishes.
- Sometimes this is not the desired action. Setting ``exit_all`` will
- instead make fio terminate all jobs in the same group. The option
- ``exit_what`` allows to control which jobs get terminated when ``exitall`` is
- enabled. The default is ``group`` and does not change the behaviour of
- ``exitall``. The setting ``all`` terminates all jobs. The setting ``stonewall``
- terminates all currently running jobs across all groups and continues execution
- with the next stonewalled group.
-
-.. option:: exec_prerun=str
-
- Before running this job, issue the command specified through
- :manpage:`system(3)`. Output is redirected in a file called
- :file:`jobname.prerun.txt`.
-
-.. option:: exec_postrun=str
-
- After the job completes, issue the command specified though
- :manpage:`system(3)`. Output is redirected in a file called
- :file:`jobname.postrun.txt`.
-
-.. option:: uid=int
-
- Instead of running as the invoking user, set the user ID to this value
- before the thread/process does any work.
-
-.. option:: gid=int
-
- Set group ID, see :option:`uid`.
-
-
-Verification
-~~~~~~~~~~~~
-
-.. option:: verify_only
-
- Do not perform specified workload, only verify data still matches previous
- invocation of this workload. This option allows one to check data multiple
- times at a later date without overwriting it. This option makes sense only
- for workloads that write data, and does not support workloads with the
- :option:`time_based` option set.
-
-.. option:: do_verify=bool
-
- Run the verify phase after a write phase. Only valid if :option:`verify` is
- set. Default: true.
-
-.. option:: verify=str
-
- If writing to a file, fio can verify the file contents after each iteration
- of the job. Each verification method also implies verification of special
- header, which is written to the beginning of each block. This header also
- includes meta information, like offset of the block, block number, timestamp
- when block was written, etc. :option:`verify` can be combined with
- :option:`verify_pattern` option. The allowed values are:
-
- **md5**
- Use an md5 sum of the data area and store it in the header of
- each block.
-
- **crc64**
- Use an experimental crc64 sum of the data area and store it in the
- header of each block.
-
- **crc32c**
- Use a crc32c sum of the data area and store it in the header of
- each block. This will automatically use hardware acceleration
- (e.g. SSE4.2 on an x86 or CRC crypto extensions on ARM64) but will
- fall back to software crc32c if none is found. Generally the
- fastest checksum fio supports when hardware accelerated.
-
- **crc32c-intel**
- Synonym for crc32c.
-
- **crc32**
- Use a crc32 sum of the data area and store it in the header of each
- block.
-
- **crc16**
- Use a crc16 sum of the data area and store it in the header of each
- block.
-
- **crc7**
- Use a crc7 sum of the data area and store it in the header of each
- block.
-
- **xxhash**
- Use xxhash as the checksum function. Generally the fastest software
- checksum that fio supports.
-
- **sha512**
- Use sha512 as the checksum function.
-
- **sha256**
- Use sha256 as the checksum function.
-
- **sha1**
- Use optimized sha1 as the checksum function.
-
- **sha3-224**
- Use optimized sha3-224 as the checksum function.
-
- **sha3-256**
- Use optimized sha3-256 as the checksum function.
-
- **sha3-384**
- Use optimized sha3-384 as the checksum function.
-
- **sha3-512**
- Use optimized sha3-512 as the checksum function.
-
- **meta**
- This option is deprecated, since now meta information is included in
- generic verification header and meta verification happens by
- default. For detailed information see the description of the
- :option:`verify` setting. This option is kept because of
- compatibility's sake with old configurations. Do not use it.
-
- **pattern**
- Verify a strict pattern. Normally fio includes a header with some
- basic information and checksumming, but if this option is set, only
- the specific pattern set with :option:`verify_pattern` is verified.
-
- **null**
- Only pretend to verify. Useful for testing internals with
- :option:`ioengine`\=null, not for much else.
-
- This option can be used for repeated burn-in tests of a system to make sure
- that the written data is also correctly read back. If the data direction
- given is a read or random read, fio will assume that it should verify a
- previously written file. If the data direction includes any form of write,
- the verify will be of the newly written data.
-
- To avoid false verification errors, do not use the norandommap option when
- verifying data with async I/O engines and I/O depths > 1. Or use the
- norandommap and the lfsr random generator together to avoid writing to the
- same offset with muliple outstanding I/Os.
-
-.. option:: verify_offset=int
-
- Swap the verification header with data somewhere else in the block before
- writing. It is swapped back before verifying.
-
-.. option:: verify_interval=int
-
- Write the verification header at a finer granularity than the
- :option:`blocksize`. It will be written for chunks the size of
- ``verify_interval``. :option:`blocksize` should divide this evenly.
-
-.. option:: verify_pattern=str
-
- If set, fio will fill the I/O buffers with this pattern. Fio defaults to
- filling with totally random bytes, but sometimes it's interesting to fill
- with a known pattern for I/O verification purposes. Depending on the width
- of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it can
- be either a decimal or a hex number). The ``verify_pattern`` if larger than
- a 32-bit quantity has to be a hex number that starts with either "0x" or
- "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o
- format, which means that for each block offset will be written and then
- verified back, e.g.::
-
- verify_pattern=%o
-
- Or use combination of everything::
-
- verify_pattern=0xff%o"abcd"-12
-
-.. option:: verify_fatal=bool
-
- Normally fio will keep checking the entire contents before quitting on a
- block verification failure. If this option is set, fio will exit the job on
- the first observed failure. Default: false.
-
-.. option:: verify_dump=bool
-
- If set, dump the contents of both the original data block and the data block
- we read off disk to files. This allows later analysis to inspect just what
- kind of data corruption occurred. Off by default.
-
-.. option:: verify_async=int
-
- Fio will normally verify I/O inline from the submitting thread. This option
- takes an integer describing how many async offload threads to create for I/O
- verification instead, causing fio to offload the duty of verifying I/O
- contents to one or more separate threads. If using this offload option, even
- sync I/O engines can benefit from using an :option:`iodepth` setting higher
- than 1, as it allows them to have I/O in flight while verifies are running.
- Defaults to 0 async threads, i.e. verification is not asynchronous.
-
-.. option:: verify_async_cpus=str
-
- Tell fio to set the given CPU affinity on the async I/O verification
- threads. See :option:`cpus_allowed` for the format used.
-
-.. option:: verify_backlog=int
-
- Fio will normally verify the written contents of a job that utilizes verify
- once that job has completed. In other words, everything is written then
- everything is read back and verified. You may want to verify continually
- instead for a variety of reasons. Fio stores the meta data associated with
- an I/O block in memory, so for large verify workloads, quite a bit of memory
- would be used up holding this meta data. If this option is enabled, fio will
- write only N blocks before verifying these blocks.
-
-.. option:: verify_backlog_batch=int
-
- Control how many blocks fio will verify if :option:`verify_backlog` is
- set. If not set, will default to the value of :option:`verify_backlog`
- (meaning the entire queue is read back and verified). If
- ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all
- blocks will be verified, if ``verify_backlog_batch`` is larger than
- :option:`verify_backlog`, some blocks will be verified more than once.
-
-.. option:: verify_state_save=bool
-
- When a job exits during the write phase of a verify workload, save its
- current state. This allows fio to replay up until that point, if the verify
- state is loaded for the verify read phase. The format of the filename is,
- roughly::
-
- <type>-<jobname>-<jobindex>-verify.state.
-
- <type> is "local" for a local run, "sock" for a client/server socket
- connection, and "ip" (192.168.0.1, for instance) for a networked
- client/server connection. Defaults to true.
-
-.. option:: verify_state_load=bool
-
- If a verify termination trigger was used, fio stores the current write state
- of each thread. This can be used at verification time so that fio knows how
- far it should verify. Without this information, fio will run a full
- verification pass, according to the settings in the job file used. Default
- false.
-
-.. option:: trim_percentage=int
-
- Number of verify blocks to discard/trim.
-
-.. option:: trim_verify_zero=bool
-
- Verify that trim/discarded blocks are returned as zeros.
-
-.. option:: trim_backlog=int
-
- Trim after this number of blocks are written.
-
-.. option:: trim_backlog_batch=int
-
- Trim this number of I/O blocks.
-
-.. option:: experimental_verify=bool
-
- Enable experimental verification.
-
-Steady state
-~~~~~~~~~~~~
-
-.. option:: steadystate=str:float, ss=str:float
-
- Define the criterion and limit for assessing steady state performance. The
- first parameter designates the criterion whereas the second parameter sets
- the threshold. When the criterion falls below the threshold for the
- specified duration, the job will stop. For example, `iops_slope:0.1%` will
- direct fio to terminate the job when the least squares regression slope
- falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled
- this will apply to all jobs in the group. Below is the list of available
- steady state assessment criteria. All assessments are carried out using only
- data from the rolling collection window. Threshold limits can be expressed
- as a fixed value or as a percentage of the mean in the collection window.
-
- When using this feature, most jobs should include the :option:`time_based`
- and :option:`runtime` options or the :option:`loops` option so that fio does not
- stop running after it has covered the full size of the specified file(s) or device(s).
-
- **iops**
- Collect IOPS data. Stop the job if all individual IOPS measurements
- are within the specified limit of the mean IOPS (e.g., ``iops:2``
- means that all individual IOPS values must be within 2 of the mean,
- whereas ``iops:0.2%`` means that all individual IOPS values must be
- within 0.2% of the mean IOPS to terminate the job).
-
- **iops_slope**
- Collect IOPS data and calculate the least squares regression
- slope. Stop the job if the slope falls below the specified limit.
-
- **bw**
- Collect bandwidth data. Stop the job if all individual bandwidth
- measurements are within the specified limit of the mean bandwidth.
-
- **bw_slope**
- Collect bandwidth data and calculate the least squares regression
- slope. Stop the job if the slope falls below the specified limit.
-
-.. option:: steadystate_duration=time, ss_dur=time
-
- A rolling window of this duration will be used to judge whether steady state
- has been reached. Data will be collected once per second. The default is 0
- which disables steady state detection. When the unit is omitted, the
- value is interpreted in seconds.
-
-.. option:: steadystate_ramp_time=time, ss_ramp=time
-
- Allow the job to run for the specified duration before beginning data
- collection for checking the steady state job termination criterion. The
- default is 0. When the unit is omitted, the value is interpreted in seconds.
-
-
-Measurements and reporting
-~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. option:: per_job_logs=bool
-
- If set, this generates bw/clat/iops log with per file private filenames. If
- not set, jobs with identical names will share the log filename. Default:
- true.
-
-.. option:: group_reporting
-
- It may sometimes be interesting to display statistics for groups of jobs as
- a whole instead of for each individual job. This is especially true if
- :option:`numjobs` is used; looking at individual thread/process output
- quickly becomes unwieldy. To see the final report per-group instead of
- per-job, use :option:`group_reporting`. Jobs in a file will be part of the
- same reporting group, unless if separated by a :option:`stonewall`, or by
- using :option:`new_group`.
-
-.. option:: new_group
-
- Start a new reporting group. See: :option:`group_reporting`. If not given,
- all jobs in a file will be part of the same reporting group, unless
- separated by a :option:`stonewall`.
-
-.. option:: stats=bool
-
- By default, fio collects and shows final output results for all jobs
- that run. If this option is set to 0, then fio will ignore it in
- the final stat output.
-
-.. option:: write_bw_log=str
-
- If given, write a bandwidth log for this job. Can be used to store data of
- the bandwidth of the jobs in their lifetime.
-
- If no str argument is given, the default filename of
- :file:`jobname_type.x.log` is used. Even when the argument is given, fio
- will still append the type of log. So if one specifies::
-
- write_bw_log=foo
-
- The actual log name will be :file:`foo_bw.x.log` where `x` is the index
- of the job (`1..N`, where `N` is the number of jobs). If
- :option:`per_job_logs` is false, then the filename will not include the
- `.x` job index.
-
- The included :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
- text files into nice graphs. See `Log File Formats`_ for how data is
- structured within the file.
-
-.. option:: write_lat_log=str
-
- Same as :option:`write_bw_log`, except this option creates I/O
- submission (e.g., :file:`name_slat.x.log`), completion (e.g.,
- :file:`name_clat.x.log`), and total (e.g., :file:`name_lat.x.log`)
- latency files instead. See :option:`write_bw_log` for details about
- the filename format and `Log File Formats`_ for how data is structured
- within the files.
-
-.. option:: write_hist_log=str
-
- Same as :option:`write_bw_log` but writes an I/O completion latency
- histogram file (e.g., :file:`name_hist.x.log`) instead. Note that this
- file will be empty unless :option:`log_hist_msec` has also been set.
- See :option:`write_bw_log` for details about the filename format and
- `Log File Formats`_ for how data is structured within the file.
-
-.. option:: write_iops_log=str
-
- Same as :option:`write_bw_log`, but writes an IOPS file (e.g.
- :file:`name_iops.x.log`) instead. Because fio defaults to individual
- I/O logging, the value entry in the IOPS log will be 1 unless windowed
- logging (see :option:`log_avg_msec`) has been enabled. See
- :option:`write_bw_log` for details about the filename format and `Log
- File Formats`_ for how data is structured within the file.
-
-.. option:: log_entries=int
-
- By default, fio will log an entry in the iops, latency, or bw log for
- every I/O that completes. The initial number of I/O log entries is 1024.
- When the log entries are all used, new log entries are dynamically
- allocated. This dynamic log entry allocation may negatively impact
- time-related statistics such as I/O tail latencies (e.g. 99.9th percentile
- completion latency). This option allows specifying a larger initial
- number of log entries to avoid run-time allocations of new log entries,
- resulting in more precise time-related I/O statistics.
- Also see :option:`log_avg_msec`. Defaults to 1024.
-
-.. option:: log_avg_msec=int
-
- By default, fio will log an entry in the iops, latency, or bw log for every
- I/O that completes. When writing to the disk log, that can quickly grow to a
- very large size. Setting this option makes fio average the each log entry
- over the specified period of time, reducing the resolution of the log. See
- :option:`log_max_value` as well. Defaults to 0, logging all entries.
- Also see `Log File Formats`_.
-
-.. option:: log_hist_msec=int
-
- Same as :option:`log_avg_msec`, but logs entries for completion latency
- histograms. Computing latency percentiles from averages of intervals using
- :option:`log_avg_msec` is inaccurate. Setting this option makes fio log
- histogram entries over the specified period of time, reducing log sizes for
- high IOPS devices while retaining percentile accuracy. See
- :option:`log_hist_coarseness` and :option:`write_hist_log` as well.
- Defaults to 0, meaning histogram logging is disabled.
-
-.. option:: log_hist_coarseness=int
-
- Integer ranging from 0 to 6, defining the coarseness of the resolution of
- the histogram logs enabled with :option:`log_hist_msec`. For each increment
- in coarseness, fio outputs half as many bins. Defaults to 0, for which
- histogram logs contain 1216 latency bins. See :option:`write_hist_log`
- and `Log File Formats`_.
-
-.. option:: log_max_value=bool
-
- If :option:`log_avg_msec` is set, fio logs the average over that window. If
- you instead want to log the maximum value, set this option to 1. Defaults to
- 0, meaning that averaged values are logged.
-
-.. option:: log_offset=bool
-
- If this is set, the iolog options will include the byte offset for the I/O
- entry as well as the other data values. Defaults to 0 meaning that
- offsets are not present in logs. Also see `Log File Formats`_.
-
-.. option:: log_compression=int
-
- If this is set, fio will compress the I/O logs as it goes, to keep the
- memory footprint lower. When a log reaches the specified size, that chunk is
- removed and compressed in the background. Given that I/O logs are fairly
- highly compressible, this yields a nice memory savings for longer runs. The
- downside is that the compression will consume some background CPU cycles, so
- it may impact the run. This, however, is also true if the logging ends up
- consuming most of the system memory. So pick your poison. The I/O logs are
- saved normally at the end of a run, by decompressing the chunks and storing
- them in the specified log file. This feature depends on the availability of
- zlib.
-
-.. option:: log_compression_cpus=str
-
- Define the set of CPUs that are allowed to handle online log compression for
- the I/O jobs. This can provide better isolation between performance
- sensitive jobs, and background compression work. See
- :option:`cpus_allowed` for the format used.
-
-.. option:: log_store_compressed=bool
-
- If set, fio will store the log files in a compressed format. They can be
- decompressed with fio, using the :option:`--inflate-log` command line
- parameter. The files will be stored with a :file:`.fz` suffix.
-
-.. option:: log_unix_epoch=bool
-
- If set, fio will log Unix timestamps to the log files produced by enabling
- write_type_log for each log type, instead of the default zero-based
- timestamps.
-
-.. option:: log_alternate_epoch=bool
-
- If set, fio will log timestamps based on the epoch used by the clock specified
- in the log_alternate_epoch_clock_id option, to the log files produced by
- enabling write_type_log for each log type, instead of the default zero-based
- timestamps.
-
-.. option:: log_alternate_epoch_clock_id=int
-
- Specifies the clock_id to be used by clock_gettime to obtain the alternate epoch
- if either log_unix_epoch or log_alternate_epoch are true. Otherwise has no
- effect. Default value is 0, or CLOCK_REALTIME.
-
-.. option:: block_error_percentiles=bool
-
- If set, record errors in trim block-sized units from writes and trims and
- output a histogram of how many trims it took to get to errors, and what kind
- of error was encountered.
-
-.. option:: bwavgtime=int
-
- Average the calculated bandwidth over the given time. Value is specified in
- milliseconds. If the job also does bandwidth logging through
- :option:`write_bw_log`, then the minimum of this option and
- :option:`log_avg_msec` will be used. Default: 500ms.
-
-.. option:: iopsavgtime=int
-
- Average the calculated IOPS over the given time. Value is specified in
- milliseconds. If the job also does IOPS logging through
- :option:`write_iops_log`, then the minimum of this option and
- :option:`log_avg_msec` will be used. Default: 500ms.
-
-.. option:: disk_util=bool
-
- Generate disk utilization statistics, if the platform supports it.
- Default: true.
-
-.. option:: disable_lat=bool
-
- Disable measurements of total latency numbers. Useful only for cutting back
- the number of calls to :manpage:`gettimeofday(2)`, as that does impact
- performance at really high IOPS rates. Note that to really get rid of a
- large amount of these calls, this option must be used with
- :option:`disable_slat` and :option:`disable_bw_measurement` as well.
-
-.. option:: disable_clat=bool
-
- Disable measurements of completion latency numbers. See
- :option:`disable_lat`.
-
-.. option:: disable_slat=bool
-
- Disable measurements of submission latency numbers. See
- :option:`disable_lat`.
-
-.. option:: disable_bw_measurement=bool, disable_bw=bool
-
- Disable measurements of throughput/bandwidth numbers. See
- :option:`disable_lat`.
-
-.. option:: slat_percentiles=bool
-
- Report submission latency percentiles. Submission latency is not recorded
- for synchronous ioengines.
-
-.. option:: clat_percentiles=bool
-
- Report completion latency percentiles.
-
-.. option:: lat_percentiles=bool
-
- Report total latency percentiles. Total latency is the sum of submission
- latency and completion latency.
-
-.. option:: percentile_list=float_list
-
- Overwrite the default list of percentiles for latencies and the block error
- histogram. Each number is a floating point number in the range (0,100], and
- the maximum length of the list is 20. Use ``:`` to separate the numbers. For
- example, ``--percentile_list=99.5:99.9`` will cause fio to report the
- latency durations below which 99.5% and 99.9% of the observed latencies fell,
- respectively.
-
-.. option:: significant_figures=int
-
- If using :option:`--output-format` of `normal`, set the significant
- figures to this value. Higher values will yield more precise IOPS and
- throughput units, while lower values will round. Requires a minimum
- value of 1 and a maximum value of 10. Defaults to 4.
-
-
-Error handling
-~~~~~~~~~~~~~~
-
-.. option:: exitall_on_error
-
- When one job finishes in error, terminate the rest. The default is to wait
- for each job to finish.
-
-.. option:: continue_on_error=str
-
- Normally fio will exit the job on the first observed failure. If this option
- is set, fio will continue the job when there is a 'non-fatal error' (EIO or
- EILSEQ) until the runtime is exceeded or the I/O size specified is
- completed. If this option is used, there are two more stats that are
- appended, the total error count and the first error. The error field given
- in the stats is the first error that was hit during the run.
-
- The allowed values are:
-
- **none**
- Exit on any I/O or verify errors.
-
- **read**
- Continue on read errors, exit on all others.
-
- **write**
- Continue on write errors, exit on all others.
-
- **io**
- Continue on any I/O error, exit on all others.
-
- **verify**
- Continue on verify errors, exit on all others.
-
- **all**
- Continue on all errors.
-
- **0**
- Backward-compatible alias for 'none'.
-
- **1**
- Backward-compatible alias for 'all'.
-
-.. option:: ignore_error=str
-
- Sometimes you want to ignore some errors during test in that case you can
- specify error list for each error type, instead of only being able to
- ignore the default 'non-fatal error' using :option:`continue_on_error`.
- ``ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST`` errors for
- given error type is separated with ':'. Error may be symbol ('ENOSPC',
- 'ENOMEM') or integer. Example::
-
- ignore_error=EAGAIN,ENOSPC:122
-
- This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from
- WRITE. This option works by overriding :option:`continue_on_error` with
- the list of errors for each error type if any.
-
-.. option:: error_dump=bool
-
- If set dump every error even if it is non fatal, true by default. If
- disabled only fatal error will be dumped.
-
-Running predefined workloads
-----------------------------
-
-Fio includes predefined profiles that mimic the I/O workloads generated by
-other tools.
-
-.. option:: profile=str
-
- The predefined workload to run. Current profiles are:
-
- **tiobench**
- Threaded I/O bench (tiotest/tiobench) like workload.
-
- **act**
- Aerospike Certification Tool (ACT) like workload.
-
-To view a profile's additional options use :option:`--cmdhelp` after specifying
-the profile. For example::
-
- $ fio --profile=act --cmdhelp
-
-Act profile options
-~~~~~~~~~~~~~~~~~~~
-
-.. option:: device-names=str
- :noindex:
-
- Devices to use.
-
-.. option:: load=int
- :noindex:
-
- ACT load multiplier. Default: 1.
-
-.. option:: test-duration=time
- :noindex:
-
- How long the entire test takes to run. When the unit is omitted, the value
- is given in seconds. Default: 24h.
-
-.. option:: threads-per-queue=int
- :noindex:
-
- Number of read I/O threads per device. Default: 8.
-
-.. option:: read-req-num-512-blocks=int
- :noindex:
-
- Number of 512B blocks to read at the time. Default: 3.
-
-.. option:: large-block-op-kbytes=int
- :noindex:
-
- Size of large block ops in KiB (writes). Default: 131072.
-
-.. option:: prep
- :noindex:
-
- Set to run ACT prep phase.
-
-Tiobench profile options
-~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. option:: size=str
- :noindex:
-
- Size in MiB.
-
-.. option:: block=int
- :noindex:
-
- Block size in bytes. Default: 4096.
-
-.. option:: numruns=int
- :noindex:
-
- Number of runs.
-
-.. option:: dir=str
- :noindex:
-
- Test directory.
-
-.. option:: threads=int
- :noindex:
-
- Number of threads.
-
-Interpreting the output
------------------------
-
-..
- Example output was based on the following:
- TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --time_based \
- --rate=1256k --bs=14K --name=quick --runtime=1s --name=mixed \
- --runtime=2m --rw=rw
-
-Fio spits out a lot of output. While running, fio will display the status of the
-jobs created. An example of that would be::
-
- Jobs: 1 (f=1): [_(1),M(1)][24.8%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 01m:31s]
-
-The characters inside the first set of square brackets denote the current status of
-each thread. The first character is the first job defined in the job file, and so
-forth. The possible values (in typical life cycle order) are:
-
-+------+-----+-----------------------------------------------------------+
-| Idle | Run | |
-+======+=====+===========================================================+
-| P | | Thread setup, but not started. |
-+------+-----+-----------------------------------------------------------+
-| C | | Thread created. |
-+------+-----+-----------------------------------------------------------+
-| I | | Thread initialized, waiting or generating necessary data. |
-+------+-----+-----------------------------------------------------------+
-| | p | Thread running pre-reading file(s). |
-+------+-----+-----------------------------------------------------------+
-| | / | Thread is in ramp period. |
-+------+-----+-----------------------------------------------------------+
-| | R | Running, doing sequential reads. |
-+------+-----+-----------------------------------------------------------+
-| | r | Running, doing random reads. |
-+------+-----+-----------------------------------------------------------+
-| | W | Running, doing sequential writes. |
-+------+-----+-----------------------------------------------------------+
-| | w | Running, doing random writes. |
-+------+-----+-----------------------------------------------------------+
-| | M | Running, doing mixed sequential reads/writes. |
-+------+-----+-----------------------------------------------------------+
-| | m | Running, doing mixed random reads/writes. |
-+------+-----+-----------------------------------------------------------+
-| | D | Running, doing sequential trims. |
-+------+-----+-----------------------------------------------------------+
-| | d | Running, doing random trims. |
-+------+-----+-----------------------------------------------------------+
-| | F | Running, currently waiting for :manpage:`fsync(2)`. |
-+------+-----+-----------------------------------------------------------+
-| | V | Running, doing verification of written data. |
-+------+-----+-----------------------------------------------------------+
-| f | | Thread finishing. |
-+------+-----+-----------------------------------------------------------+
-| E | | Thread exited, not reaped by main thread yet. |
-+------+-----+-----------------------------------------------------------+
-| _ | | Thread reaped. |
-+------+-----+-----------------------------------------------------------+
-| X | | Thread reaped, exited with an error. |
-+------+-----+-----------------------------------------------------------+
-| K | | Thread reaped, exited due to signal. |
-+------+-----+-----------------------------------------------------------+
-
-..
- Example output was based on the following:
- TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --runtime=58m \
- --time_based --rate=2512k --bs=256K --numjobs=10 \
- --name=readers --rw=read --name=writers --rw=write
-
-Fio will condense the thread string as not to take up more space on the command
-line than needed. For instance, if you have 10 readers and 10 writers running,
-the output would look like this::
-
- Jobs: 20 (f=20): [R(10),W(10)][4.0%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 57m:36s]
-
-Note that the status string is displayed in order, so it's possible to tell which of
-the jobs are currently doing what. In the example above this means that jobs 1--10
-are readers and 11--20 are writers.
-
-The other values are fairly self explanatory -- number of threads currently
-running and doing I/O, the number of currently open files (f=), the estimated
-completion percentage, the rate of I/O since last check (read speed listed first,
-then write speed and optionally trim speed) in terms of bandwidth and IOPS,
-and time to completion for the current running group. It's impossible to estimate
-runtime of the following groups (if any).
-
-..
- Example output was based on the following:
- TZ=UTC fio --iodepth=16 --ioengine=posixaio --filename=/tmp/fiofile \
- --direct=1 --size=100M --time_based --runtime=50s --rate_iops=89 \
- --bs=7K --name=Client1 --rw=write
-
-When fio is done (or interrupted by :kbd:`Ctrl-C`), it will show the data for
-each thread, group of threads, and disks in that order. For each overall thread (or
-group) the output looks like::
-
- Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
- write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
- slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
- clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
- lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
- clat percentiles (usec):
- | 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
- | 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
- | 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
- | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
- | 99.99th=[78119]
- bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
- iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
- lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
- lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
- lat (msec) : 100=0.65%
- cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
- IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
- submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
- complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
- issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
- latency : target=0, window=0, percentile=100.00%, depth=8
-
-The job name (or first job's name when using :option:`group_reporting`) is printed,
-along with the group id, count of jobs being aggregated, last error id seen (which
-is 0 when there are no errors), pid/tid of that thread and the time the job/group
-completed. Below are the I/O statistics for each data direction performed (showing
-writes in the example above). In the order listed, they denote:
-
-**read/write/trim**
- The string before the colon shows the I/O direction the statistics
- are for. **IOPS** is the average I/Os performed per second. **BW**
- is the average bandwidth rate shown as: value in power of 2 format
- (value in power of 10 format). The last two values show: (**total
- I/O performed** in power of 2 format / **runtime** of that thread).
-
-**slat**
- Submission latency (**min** being the minimum, **max** being the
- maximum, **avg** being the average, **stdev** being the standard
- deviation). This is the time it took to submit the I/O. For
- sync I/O this row is not displayed as the slat is really the
- completion latency (since queue/complete is one operation there).
- This value can be in nanoseconds, microseconds or milliseconds ---
- fio will choose the most appropriate base and print that (in the
- example above nanoseconds was the best scale). Note: in :option:`--minimal` mode
- latencies are always expressed in microseconds.
-
-**clat**
- Completion latency. Same names as slat, this denotes the time from
- submission to completion of the I/O pieces. For sync I/O, clat will
- usually be equal (or very close) to 0, as the time from submit to
- complete is basically just CPU time (I/O has already been done, see slat
- explanation).
-
-**lat**
- Total latency. Same names as slat and clat, this denotes the time from
- when fio created the I/O unit to completion of the I/O operation.
-
-**bw**
- Bandwidth statistics based on samples. Same names as the xlat stats,
- but also includes the number of samples taken (**samples**) and an
- approximate percentage of total aggregate bandwidth this thread
- received in its group (**per**). This last value is only really
- useful if the threads in this group are on the same disk, since they
- are then competing for disk access.
-
-**iops**
- IOPS statistics based on samples. Same names as bw.
-
-**lat (nsec/usec/msec)**
- The distribution of I/O completion latencies. This is the time from when
- I/O leaves fio and when it gets completed. Unlike the separate
- read/write/trim sections above, the data here and in the remaining
- sections apply to all I/Os for the reporting group. 250=0.04% means that
- 0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11%
- of the I/Os required 250 to 499us for completion.
-
-**cpu**
- CPU usage. User and system time, along with the number of context
- switches this thread went through, usage of system and user time, and
- finally the number of major and minor page faults. The CPU utilization
- numbers are averages for the jobs in that reporting group, while the
- context and fault counters are summed.
-
-**IO depths**
- The distribution of I/O depths over the job lifetime. The numbers are
- divided into powers of 2 and each entry covers depths from that value
- up to those that are lower than the next entry -- e.g., 16= covers
- depths from 16 to 31. Note that the range covered by a depth
- distribution entry can be different to the range covered by the
- equivalent submit/complete distribution entry.
-
-**IO submit**
- How many pieces of I/O were submitting in a single submit call. Each
- entry denotes that amount and below, until the previous entry -- e.g.,
- 16=100% means that we submitted anywhere between 9 to 16 I/Os per submit
- call. Note that the range covered by a submit distribution entry can
- be different to the range covered by the equivalent depth distribution
- entry.
-
-**IO complete**
- Like the above submit number, but for completions instead.
-
-**IO issued rwt**
- The number of read/write/trim requests issued, and how many of them were
- short or dropped.
-
-**IO latency**
- These values are for :option:`latency_target` and related options. When
- these options are engaged, this section describes the I/O depth required
- to meet the specified latency target.
-
-..
- Example output was based on the following:
- TZ=UTC fio --ioengine=null --iodepth=2 --size=100M --numjobs=2 \
- --rate_process=poisson --io_limit=32M --name=read --bs=128k \
- --rate=11M --name=write --rw=write --bs=2k --rate=700k
-
-After each client has been listed, the group statistics are printed. They
-will look like this::
-
- Run status group 0 (all jobs):
- READ: bw=20.9MiB/s (21.9MB/s), 10.4MiB/s-10.8MiB/s (10.9MB/s-11.3MB/s), io=64.0MiB (67.1MB), run=2973-3069msec
- WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
-
-For each data direction it prints:
-
-**bw**
- Aggregate bandwidth of threads in this group followed by the
- minimum and maximum bandwidth of all the threads in this group.
- Values outside of brackets are power-of-2 format and those
- within are the equivalent value in a power-of-10 format.
-**io**
- Aggregate I/O performed of all threads in this group. The
- format is the same as bw.
-**run**
- The smallest and longest runtimes of the threads in this group.
-
-And finally, the disk statistics are printed. This is Linux specific. They will look like this::
-
- Disk stats (read/write):
- sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
-
-Each value is printed for both reads and writes, with reads first. The
-numbers denote:
-
-**ios**
- Number of I/Os performed by all groups.
-**merge**
- Number of merges performed by the I/O scheduler.
-**ticks**
- Number of ticks we kept the disk busy.
-**in_queue**
- Total time spent in the disk queue.
-**util**
- The disk utilization. A value of 100% means we kept the disk
- busy constantly, 50% would be a disk idling half of the time.
-
-It is also possible to get fio to dump the current output while it is running,
-without terminating the job. To do that, send fio the **USR1** signal. You can
-also get regularly timed dumps by using the :option:`--status-interval`
-parameter, or by creating a file in :file:`/tmp` named
-:file:`fio-dump-status`. If fio sees this file, it will unlink it and dump the
-current output status.
-
-
-Terse output
-------------
-
-For scripted usage where you typically want to generate tables or graphs of the
-results, fio can output the results in a semicolon separated format. The format
-is one long line of values, such as::
-
- 2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
- A description of this job goes here.
-
-The job description (if provided) follows on a second line for terse v2.
-It appears on the same line for other terse versions.
-
-To enable terse output, use the :option:`--minimal` or
-:option:`--output-format`\=terse command line options. The
-first value is the version of the terse output format. If the output has to be
-changed for some reason, this number will be incremented by 1 to signify that
-change.
-
-Split up, the format is as follows (comments in brackets denote when a
-field was introduced or whether it's specific to some terse version):
-
- ::
-
- terse version, fio version [v3], jobname, groupid, error
-
- READ status::
-
- Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
- Submission latency: min, max, mean, stdev (usec)
- Completion latency: min, max, mean, stdev (usec)
- Completion latency percentiles: 20 fields (see below)
- Total latency: min, max, mean, stdev (usec)
- Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
- IOPS [v5]: min, max, mean, stdev, number of samples
-
- WRITE status:
-
- ::
-
- Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
- Submission latency: min, max, mean, stdev (usec)
- Completion latency: min, max, mean, stdev (usec)
- Completion latency percentiles: 20 fields (see below)
- Total latency: min, max, mean, stdev (usec)
- Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
- IOPS [v5]: min, max, mean, stdev, number of samples
-
- TRIM status [all but version 3]:
-
- Fields are similar to READ/WRITE status.
-
- CPU usage::
-
- user, system, context switches, major faults, minor faults
-
- I/O depths::
-
- <=1, 2, 4, 8, 16, 32, >=64
-
- I/O latencies microseconds::
-
- <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
-
- I/O latencies milliseconds::
-
- <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
-
- Disk utilization [v3]::
-
- disk name, read ios, write ios, read merges, write merges, read ticks, write ticks,
- time spent in queue, disk utilization percentage
-
- Additional Info (dependent on continue_on_error, default off)::
-
- total # errors, first error code
-
- Additional Info (dependent on description being set)::
-
- Text description
-
-Completion latency percentiles can be a grouping of up to 20 sets, so for the
-terse output fio writes all of them. Each field will look like this::
-
- 1.00%=6112
-
-which is the Xth percentile, and the `usec` latency associated with it.
-
-For `Disk utilization`, all disks used by fio are shown. So for each disk there
-will be a disk utilization section.
-
-Below is a single line containing short names for each of the fields in the
-minimal output v3, separated by semicolons::
-
- terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth_kb;read_iops;read_runtime_ms;read_slat_min_us;read_slat_max_us;read_slat_mean_us;read_slat_dev_us;read_clat_min_us;read_clat_max_us;read_clat_mean_us;read_clat_dev_us;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min_us;read_lat_max_us;read_lat_mean_us;read_lat_dev_us;read_bw_min_kb;read_bw_max_kb;read_bw_agg_pct;read_bw_mean_kb;read_bw_dev_kb;write_kb;write_bandwidth_kb;write_iops;write_runtime_ms;write_slat_min_us;write_slat_max_us;write_slat_mean_us;write_slat_dev_us;write_clat_min_us;write_clat_max_us;write_clat_mean_us;write_clat_dev_us;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min_us;write_lat_max_us;write_lat_mean_us;write_lat_dev_us;write_bw_min_kb;write_bw_max_kb;write_bw_agg_pct;write_bw_mean_kb;write_bw_dev_kb;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
-
-In client/server mode terse output differs from what appears when jobs are run
-locally. Disk utilization data is omitted from the standard terse output and
-for v3 and later appears on its own separate line at the end of each terse
-reporting cycle.
-
-
-JSON output
-------------
-
-The `json` output format is intended to be both human readable and convenient
-for automated parsing. For the most part its sections mirror those of the
-`normal` output. The `runtime` value is reported in msec and the `bw` value is
-reported in 1024 bytes per second units.
-
-
-JSON+ output
-------------
-
-The `json+` output format is identical to the `json` output format except that it
-adds a full dump of the completion latency bins. Each `bins` object contains a
-set of (key, value) pairs where keys are latency durations and values count how
-many I/Os had completion latencies of the corresponding duration. For example,
-consider:
-
- "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... }
-
-This data indicates that one I/O required 87,552ns to complete, two I/Os required
-100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
-
-Also included with fio is a Python script `fio_jsonplus_clat2csv` that takes
-json+ output and generates CSV-formatted latency data suitable for plotting.
-
-The latency durations actually represent the midpoints of latency intervals.
-For details refer to :file:`stat.h`.
-
-
-Trace file format
------------------
-
-There are two trace file format that you can encounter. The older (v1) format is
-unsupported since version 1.20-rc3 (March 2008). It will still be described
-below in case that you get an old trace and want to understand it.
-
-In any case the trace is a simple text file with a single action per line.
-
-
-Trace file format v1
-~~~~~~~~~~~~~~~~~~~~
-
-Each line represents a single I/O action in the following format::
-
- rw, offset, length
-
-where `rw=0/1` for read/write, and the `offset` and `length` entries being in bytes.
-
-This format is not supported in fio versions >= 1.20-rc3.
-
-
-Trace file format v2
-~~~~~~~~~~~~~~~~~~~~
-
-The second version of the trace file format was added in fio version 1.17. It
-allows to access more then one file per trace and has a bigger set of possible
-file actions.
-
-The first line of the trace file has to be::
-
- fio version 2 iolog
-
-Following this can be lines in two different formats, which are described below.
-
-The file management format::
-
- filename action
-
-The `filename` is given as an absolute path. The `action` can be one of these:
-
-**add**
- Add the given `filename` to the trace.
-**open**
- Open the file with the given `filename`. The `filename` has to have
- been added with the **add** action before.
-**close**
- Close the file with the given `filename`. The file has to have been
- opened before.
-
-
-The file I/O action format::
-
- filename action offset length
-
-The `filename` is given as an absolute path, and has to have been added and
-opened before it can be used with this format. The `offset` and `length` are
-given in bytes. The `action` can be one of these:
-
-**wait**
- Wait for `offset` microseconds. Everything below 100 is discarded.
- The time is relative to the previous `wait` statement.
-**read**
- Read `length` bytes beginning from `offset`.
-**write**
- Write `length` bytes beginning from `offset`.
-**sync**
- :manpage:`fsync(2)` the file.
-**datasync**
- :manpage:`fdatasync(2)` the file.
-**trim**
- Trim the given file from the given `offset` for `length` bytes.
-
-
-I/O Replay - Merging Traces
----------------------------
-
-Colocation is a common practice used to get the most out of a machine.
-Knowing which workloads play nicely with each other and which ones don't is
-a much harder task. While fio can replay workloads concurrently via multiple
-jobs, it leaves some variability up to the scheduler making results harder to
-reproduce. Merging is a way to make the order of events consistent.
-
-Merging is integrated into I/O replay and done when a
-:option:`merge_blktrace_file` is specified. The list of files passed to
-:option:`read_iolog` go through the merge process and output a single file
-stored to the specified file. The output file is passed on as if it were the
-only file passed to :option:`read_iolog`. An example would look like::
-
- $ fio --read_iolog="<file1>:<file2>" --merge_blktrace_file="<output_file>"
-
-Creating only the merged file can be done by passing the command line argument
-:option:`--merge-blktrace-only`.
-
-Scaling traces can be done to see the relative impact of any particular trace
-being slowed down or sped up. :option:`merge_blktrace_scalars` takes in a colon
-separated list of percentage scalars. It is index paired with the files passed
-to :option:`read_iolog`.
-
-With scaling, it may be desirable to match the running time of all traces.
-This can be done with :option:`merge_blktrace_iters`. It is index paired with
-:option:`read_iolog` just like :option:`merge_blktrace_scalars`.
-
-In an example, given two traces, A and B, each 60s long. If we want to see
-the impact of trace A issuing IOs twice as fast and repeat trace A over the
-runtime of trace B, the following can be done::
-
- $ fio --read_iolog="<trace_a>:"<trace_b>" --merge_blktrace_file"<output_file>" --merge_blktrace_scalars="50:100" --merge_blktrace_iters="2:1"
-
-This runs trace A at 2x the speed twice for approximately the same runtime as
-a single run of trace B.
-
-
-CPU idleness profiling
-----------------------
-
-In some cases, we want to understand CPU overhead in a test. For example, we
-test patches for the specific goodness of whether they reduce CPU usage.
-Fio implements a balloon approach to create a thread per CPU that runs at idle
-priority, meaning that it only runs when nobody else needs the cpu.
-By measuring the amount of work completed by the thread, idleness of each CPU
-can be derived accordingly.
-
-An unit work is defined as touching a full page of unsigned characters. Mean and
-standard deviation of time to complete an unit work is reported in "unit work"
-section. Options can be chosen to report detailed percpu idleness or overall
-system idleness by aggregating percpu stats.
-
-
-Verification and triggers
--------------------------
-
-Fio is usually run in one of two ways, when data verification is done. The first
-is a normal write job of some sort with verify enabled. When the write phase has
-completed, fio switches to reads and verifies everything it wrote. The second
-model is running just the write phase, and then later on running the same job
-(but with reads instead of writes) to repeat the same I/O patterns and verify
-the contents. Both of these methods depend on the write phase being completed,
-as fio otherwise has no idea how much data was written.
-
-With verification triggers, fio supports dumping the current write state to
-local files. Then a subsequent read verify workload can load this state and know
-exactly where to stop. This is useful for testing cases where power is cut to a
-server in a managed fashion, for instance.
-
-A verification trigger consists of two things:
-
-1) Storing the write state of each job.
-2) Executing a trigger command.
-
-The write state is relatively small, on the order of hundreds of bytes to single
-kilobytes. It contains information on the number of completions done, the last X
-completions, etc.
-
-A trigger is invoked either through creation ('touch') of a specified file in
-the system, or through a timeout setting. If fio is run with
-:option:`--trigger-file`\= :file:`/tmp/trigger-file`, then it will continually
-check for the existence of :file:`/tmp/trigger-file`. When it sees this file, it
-will fire off the trigger (thus saving state, and executing the trigger
-command).
-
-For client/server runs, there's both a local and remote trigger. If fio is
-running as a server backend, it will send the job states back to the client for
-safe storage, then execute the remote trigger, if specified. If a local trigger
-is specified, the server will still send back the write state, but the client
-will then execute the trigger.
-
-Verification trigger example
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Let's say we want to run a powercut test on the remote Linux machine 'server'.
-Our write workload is in :file:`write-test.fio`. We want to cut power to 'server' at
-some point during the run, and we'll run this test from the safety or our local
-machine, 'localbox'. On the server, we'll start the fio backend normally::
-
- server# fio --server
-
-and on the client, we'll fire off the workload::
-
- localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
-
-We set :file:`/tmp/my-trigger` as the trigger file, and we tell fio to execute::
-
- echo b > /proc/sysrq-trigger
-
-on the server once it has received the trigger and sent us the write state. This
-will work, but it's not **really** cutting power to the server, it's merely
-abruptly rebooting it. If we have a remote way of cutting power to the server
-through IPMI or similar, we could do that through a local trigger command
-instead. Let's assume we have a script that does IPMI reboot of a given hostname,
-ipmi-reboot. On localbox, we could then have run fio with a local trigger
-instead::
-
- localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
-
-For this case, fio would wait for the server to send us the write state, then
-execute ``ipmi-reboot server`` when that happened.
-
-Loading verify state
-~~~~~~~~~~~~~~~~~~~~
-
-To load stored write state, a read verification job file must contain the
-:option:`verify_state_load` option. If that is set, fio will load the previously
-stored state. For a local fio run this is done by loading the files directly,
-and on a client/server run, the server backend will ask the client to send the
-files over and load them from there.
-
-
-Log File Formats
-----------------
-
-Fio supports a variety of log file formats, for logging latencies, bandwidth,
-and IOPS. The logs share a common format, which looks like this:
-
- *time* (`msec`), *value*, *data direction*, *block size* (`bytes`),
- *offset* (`bytes`), *command priority*
-
-*Time* for the log entry is always in milliseconds. The *value* logged depends
-on the type of log, it will be one of the following:
-
- **Latency log**
- Value is latency in nsecs
- **Bandwidth log**
- Value is in KiB/sec
- **IOPS log**
- Value is IOPS
-
-*Data direction* is one of the following:
-
- **0**
- I/O is a READ
- **1**
- I/O is a WRITE
- **2**
- I/O is a TRIM
-
-The entry's *block size* is always in bytes. The *offset* is the position in bytes
-from the start of the file for that particular I/O. The logging of the offset can be
-toggled with :option:`log_offset`.
-
-*Command priority* is 0 for normal priority and 1 for high priority. This is controlled
-by the ioengine specific :option:`cmdprio_percentage`.
-
-Fio defaults to logging every individual I/O but when windowed logging is set
-through :option:`log_avg_msec`, either the average (by default) or the maximum
-(:option:`log_max_value` is set) *value* seen over the specified period of time
-is recorded. Each *data direction* seen within the window period will aggregate
-its values in a separate row. Further, when using windowed logging the *block
-size* and *offset* entries will always contain 0.
-
-
-Client/Server
--------------
-
-Normally fio is invoked as a stand-alone application on the machine where the
-I/O workload should be generated. However, the backend and frontend of fio can
-be run separately i.e., the fio server can generate an I/O workload on the "Device
-Under Test" while being controlled by a client on another machine.
-
-Start the server on the machine which has access to the storage DUT::
-
- $ fio --server=args
-
-where `args` defines what fio listens to. The arguments are of the form
-``type,hostname`` or ``IP,port``. *type* is either ``ip`` (or ip4) for TCP/IP
-v4, ``ip6`` for TCP/IP v6, or ``sock`` for a local unix domain socket.
-*hostname* is either a hostname or IP address, and *port* is the port to listen
-to (only valid for TCP/IP, not a local socket). Some examples:
-
-1) ``fio --server``
-
- Start a fio server, listening on all interfaces on the default port (8765).
-
-2) ``fio --server=ip:hostname,4444``
-
- Start a fio server, listening on IP belonging to hostname and on port 4444.
-
-3) ``fio --server=ip6:::1,4444``
-
- Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
-
-4) ``fio --server=,4444``
-
- Start a fio server, listening on all interfaces on port 4444.
-
-5) ``fio --server=1.2.3.4``
-
- Start a fio server, listening on IP 1.2.3.4 on the default port.
-
-6) ``fio --server=sock:/tmp/fio.sock``
-
- Start a fio server, listening on the local socket :file:`/tmp/fio.sock`.
-
-Once a server is running, a "client" can connect to the fio server with::
-
- fio <local-args> --client=<server> <remote-args> <job file(s)>
-
-where `local-args` are arguments for the client where it is running, `server`
-is the connect string, and `remote-args` and `job file(s)` are sent to the
-server. The `server` string follows the same format as it does on the server
-side, to allow IP/hostname/socket and port strings.
-
-Fio can connect to multiple servers this way::
-
- fio --client=<server1> <job file(s)> --client=<server2> <job file(s)>
-
-If the job file is located on the fio server, then you can tell the server to
-load a local file as well. This is done by using :option:`--remote-config` ::
-
- fio --client=server --remote-config /path/to/file.fio
-
-Then fio will open this local (to the server) job file instead of being passed
-one from the client.
-
-If you have many servers (example: 100 VMs/containers), you can input a pathname
-of a file containing host IPs/names as the parameter value for the
-:option:`--client` option. For example, here is an example :file:`host.list`
-file containing 2 hostnames::
-
- host1.your.dns.domain
- host2.your.dns.domain
-
-The fio command would then be::
-
- fio --client=host.list <job file(s)>
-
-In this mode, you cannot input server-specific parameters or job files -- all
-servers receive the same job file.
-
-In order to let ``fio --client`` runs use a shared filesystem from multiple
-hosts, ``fio --client`` now prepends the IP address of the server to the
-filename. For example, if fio is using the directory :file:`/mnt/nfs/fio` and is
-writing filename :file:`fileio.tmp`, with a :option:`--client` `hostfile`
-containing two hostnames ``h1`` and ``h2`` with IP addresses 192.168.10.120 and
-192.168.10.121, then fio will create two files::
-
- /mnt/nfs/fio/192.168.10.120.fileio.tmp
- /mnt/nfs/fio/192.168.10.121.fileio.tmp
-
-Terse output in client/server mode will differ slightly from what is produced
-when fio is run in stand-alone mode. See the terse output section for details.
--- /dev/null
+How fio works
+-------------
+
+The first step in getting fio to simulate a desired I/O workload, is writing a
+job file describing that specific setup. A job file may contain any number of
+threads and/or files -- the typical contents of the job file is a *global*
+section defining shared parameters, and one or more job sections describing the
+jobs involved. When run, fio parses this file and sets everything up as
+described. If we break down a job from top to bottom, it contains the following
+basic parameters:
+
+`I/O type`_
+
+ Defines the I/O pattern issued to the file(s). We may only be reading
+ sequentially from this file(s), or we may be writing randomly. Or even
+ mixing reads and writes, sequentially or randomly.
+ Should we be doing buffered I/O, or direct/raw I/O?
+
+`Block size`_
+
+ In how large chunks are we issuing I/O? This may be a single value,
+ or it may describe a range of block sizes.
+
+`I/O size`_
+
+ How much data are we going to be reading/writing.
+
+`I/O engine`_
+
+ How do we issue I/O? We could be memory mapping the file, we could be
+ using regular read/write, we could be using splice, async I/O, or even
+ SG (SCSI generic sg).
+
+`I/O depth`_
+
+ If the I/O engine is async, how large a queuing depth do we want to
+ maintain?
+
+
+`Target file/device`_
+
+ How many files are we spreading the workload over.
+
+`Threads, processes and job synchronization`_
+
+ How many threads or processes should we spread this workload over.
+
+The above are the basic parameters defined for a workload, in addition there's a
+multitude of parameters that modify other aspects of how this job behaves.
+
+
+Command line options
+--------------------
+
+.. option:: --debug=type
+
+ Enable verbose tracing `type` of various fio actions. May be ``all`` for all types
+ or individual types separated by a comma (e.g. ``--debug=file,mem`` will
+ enable file and memory debugging). Currently, additional logging is
+ available for:
+
+ *process*
+ Dump info related to processes.
+ *file*
+ Dump info related to file actions.
+ *io*
+ Dump info related to I/O queuing.
+ *mem*
+ Dump info related to memory allocations.
+ *blktrace*
+ Dump info related to blktrace setup.
+ *verify*
+ Dump info related to I/O verification.
+ *all*
+ Enable all debug options.
+ *random*
+ Dump info related to random offset generation.
+ *parse*
+ Dump info related to option matching and parsing.
+ *diskutil*
+ Dump info related to disk utilization updates.
+ *job:x*
+ Dump info only related to job number x.
+ *mutex*
+ Dump info only related to mutex up/down ops.
+ *profile*
+ Dump info related to profile extensions.
+ *time*
+ Dump info related to internal time keeping.
+ *net*
+ Dump info related to networking connections.
+ *rate*
+ Dump info related to I/O rate switching.
+ *compress*
+ Dump info related to log compress/decompress.
+ *steadystate*
+ Dump info related to steadystate detection.
+ *helperthread*
+ Dump info related to the helper thread.
+ *zbd*
+ Dump info related to support for zoned block devices.
+ *?* or *help*
+ Show available debug options.
+
+.. option:: --parse-only
+
+ Parse options only, don't start any I/O.
+
+.. option:: --merge-blktrace-only
+
+ Merge blktraces only, don't start any I/O.
+
+.. option:: --output=filename
+
+ Write output to file `filename`.
+
+.. option:: --output-format=format
+
+ Set the reporting `format` to `normal`, `terse`, `json`, or `json+`. Multiple
+ formats can be selected, separated by a comma. `terse` is a CSV based
+ format. `json+` is like `json`, except it adds a full dump of the latency
+ buckets.
+
+.. option:: --bandwidth-log
+
+ Generate aggregate bandwidth logs.
+
+.. option:: --minimal
+
+ Print statistics in a terse, semicolon-delimited format.
+
+.. option:: --append-terse
+
+ Print statistics in selected mode AND terse, semicolon-delimited format.
+ **Deprecated**, use :option:`--output-format` instead to select multiple
+ formats.
+
+.. option:: --terse-version=version
+
+ Set terse `version` output format (default 3, or 2 or 4 or 5).
+
+.. option:: --version
+
+ Print version information and exit.
+
+.. option:: --help
+
+ Print a summary of the command line options and exit.
+
+.. option:: --cpuclock-test
+
+ Perform test and validation of internal CPU clock.
+
+.. option:: --crctest=[test]
+
+ Test the speed of the built-in checksumming functions. If no argument is
+ given, all of them are tested. Alternatively, a comma separated list can
+ be passed, in which case the given ones are tested.
+
+.. option:: --cmdhelp=command
+
+ Print help information for `command`. May be ``all`` for all commands.
+
+.. option:: --enghelp=[ioengine[,command]]
+
+ List all commands defined by `ioengine`, or print help for `command`
+ defined by `ioengine`. If no `ioengine` is given, list all
+ available ioengines.
+
+.. option:: --showcmd=jobfile
+
+ Convert `jobfile` to a set of command-line options.
+
+.. option:: --readonly
+
+ Turn on safety read-only checks, preventing writes and trims. The
+ ``--readonly`` option is an extra safety guard to prevent users from
+ accidentally starting a write or trim workload when that is not desired.
+ Fio will only modify the device under test if
+ `rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite` is given. This
+ safety net can be used as an extra precaution.
+
+.. option:: --eta=when
+
+ Specifies when real-time ETA estimate should be printed. `when` may be
+ `always`, `never` or `auto`. `auto` is the default, it prints ETA
+ when requested if the output is a TTY. `always` disregards the output
+ type, and prints ETA when requested. `never` never prints ETA.
+
+.. option:: --eta-interval=time
+
+ By default, fio requests client ETA status roughly every second. With
+ this option, the interval is configurable. Fio imposes a minimum
+ allowed time to avoid flooding the console, less than 250 msec is
+ not supported.
+
+.. option:: --eta-newline=time
+
+ Force a new line for every `time` period passed. When the unit is omitted,
+ the value is interpreted in seconds.
+
+.. option:: --status-interval=time
+
+ Force a full status dump of cumulative (from job start) values at `time`
+ intervals. This option does *not* provide per-period measurements. So
+ values such as bandwidth are running averages. When the time unit is omitted,
+ `time` is interpreted in seconds. Note that using this option with
+ ``--output-format=json`` will yield output that technically isn't valid
+ json, since the output will be collated sets of valid json. It will need
+ to be split into valid sets of json after the run.
+
+.. option:: --section=name
+
+ Only run specified section `name` in job file. Multiple sections can be specified.
+ The ``--section`` option allows one to combine related jobs into one file.
+ E.g. one job file could define light, moderate, and heavy sections. Tell
+ fio to run only the "heavy" section by giving ``--section=heavy``
+ command line option. One can also specify the "write" operations in one
+ section and "verify" operation in another section. The ``--section`` option
+ only applies to job sections. The reserved *global* section is always
+ parsed and used.
+
+.. option:: --alloc-size=kb
+
+ Allocate additional internal smalloc pools of size `kb` in KiB. The
+ ``--alloc-size`` option increases shared memory set aside for use by fio.
+ If running large jobs with randommap enabled, fio can run out of memory.
+ Smalloc is an internal allocator for shared structures from a fixed size
+ memory pool and can grow to 16 pools. The pool size defaults to 16MiB.
+
+ NOTE: While running :file:`.fio_smalloc.*` backing store files are visible
+ in :file:`/tmp`.
+
+.. option:: --warnings-fatal
+
+ All fio parser warnings are fatal, causing fio to exit with an
+ error.
+
+.. option:: --max-jobs=nr
+
+ Set the maximum number of threads/processes to support to `nr`.
+ NOTE: On Linux, it may be necessary to increase the shared-memory
+ limit (:file:`/proc/sys/kernel/shmmax`) if fio runs into errors while
+ creating jobs.
+
+.. option:: --server=args
+
+ Start a backend server, with `args` specifying what to listen to.
+ See `Client/Server`_ section.
+
+.. option:: --daemonize=pidfile
+
+ Background a fio server, writing the pid to the given `pidfile` file.
+
+.. option:: --client=hostname
+
+ Instead of running the jobs locally, send and run them on the given `hostname`
+ or set of `hostname`\s. See `Client/Server`_ section.
+
+.. option:: --remote-config=file
+
+ Tell fio server to load this local `file`.
+
+.. option:: --idle-prof=option
+
+ Report CPU idleness. `option` is one of the following:
+
+ **calibrate**
+ Run unit work calibration only and exit.
+
+ **system**
+ Show aggregate system idleness and unit work.
+
+ **percpu**
+ As **system** but also show per CPU idleness.
+
+.. option:: --inflate-log=log
+
+ Inflate and output compressed `log`.
+
+.. option:: --trigger-file=file
+
+ Execute trigger command when `file` exists.
+
+.. option:: --trigger-timeout=time
+
+ Execute trigger at this `time`.
+
+.. option:: --trigger=command
+
+ Set this `command` as local trigger.
+
+.. option:: --trigger-remote=command
+
+ Set this `command` as remote trigger.
+
+.. option:: --aux-path=path
+
+ Use the directory specified by `path` for generated state files instead
+ of the current working directory.
+
+Any parameters following the options will be assumed to be job files, unless
+they match a job file parameter. Multiple job files can be listed and each job
+file will be regarded as a separate group. Fio will :option:`stonewall`
+execution between each group.
+
+
+Job file format
+---------------
+
+As previously described, fio accepts one or more job files describing what it is
+supposed to do. The job file format is the classic ini file, where the names
+enclosed in [] brackets define the job name. You are free to use any ASCII name
+you want, except *global* which has special meaning. Following the job name is
+a sequence of zero or more parameters, one per line, that define the behavior of
+the job. If the first character in a line is a ';' or a '#', the entire line is
+discarded as a comment.
+
+A *global* section sets defaults for the jobs described in that file. A job may
+override a *global* section parameter, and a job file may even have several
+*global* sections if so desired. A job is only affected by a *global* section
+residing above it.
+
+The :option:`--cmdhelp` option also lists all options. If used with a `command`
+argument, :option:`--cmdhelp` will detail the given `command`.
+
+See the `examples/` directory for inspiration on how to write job files. Note
+the copyright and license requirements currently apply to `examples/` files.
+
+So let's look at a really simple job file that defines two processes, each
+randomly reading from a 128MiB file:
+
+.. code-block:: ini
+
+ ; -- start job file --
+ [global]
+ rw=randread
+ size=128m
+
+ [job1]
+
+ [job2]
+
+ ; -- end job file --
+
+As you can see, the job file sections themselves are empty as all the described
+parameters are shared. As no :option:`filename` option is given, fio makes up a
+`filename` for each of the jobs as it sees fit. On the command line, this job
+would look as follows::
+
+$ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
+
+
+Let's look at an example that has a number of processes writing randomly to
+files:
+
+.. code-block:: ini
+
+ ; -- start job file --
+ [random-writers]
+ ioengine=libaio
+ iodepth=4
+ rw=randwrite
+ bs=32k
+ direct=0
+ size=64m
+ numjobs=4
+ ; -- end job file --
+
+Here we have no *global* section, as we only have one job defined anyway. We
+want to use async I/O here, with a depth of 4 for each file. We also increased
+the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical
+jobs. The result is 4 processes each randomly writing to their own 64MiB
+file. Instead of using the above job file, you could have given the parameters
+on the command line. For this case, you would specify::
+
+$ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
+
+When fio is utilized as a basis of any reasonably large test suite, it might be
+desirable to share a set of standardized settings across multiple job files.
+Instead of copy/pasting such settings, any section may pull in an external
+:file:`filename.fio` file with *include filename* directive, as in the following
+example::
+
+ ; -- start job file including.fio --
+ [global]
+ filename=/tmp/test
+ filesize=1m
+ include glob-include.fio
+
+ [test]
+ rw=randread
+ bs=4k
+ time_based=1
+ runtime=10
+ include test-include.fio
+ ; -- end job file including.fio --
+
+.. code-block:: ini
+
+ ; -- start job file glob-include.fio --
+ thread=1
+ group_reporting=1
+ ; -- end job file glob-include.fio --
+
+.. code-block:: ini
+
+ ; -- start job file test-include.fio --
+ ioengine=libaio
+ iodepth=4
+ ; -- end job file test-include.fio --
+
+Settings pulled into a section apply to that section only (except *global*
+section). Include directives may be nested in that any included file may contain
+further include directive(s). Include files may not contain [] sections.
+
+
+Environment variables
+~~~~~~~~~~~~~~~~~~~~~
+
+Fio also supports environment variable expansion in job files. Any sub-string of
+the form ``${VARNAME}`` as part of an option value (in other words, on the right
+of the '='), will be expanded to the value of the environment variable called
+`VARNAME`. If no such environment variable is defined, or `VARNAME` is the
+empty string, the empty string will be substituted.
+
+As an example, let's look at a sample fio invocation and job file::
+
+$ SIZE=64m NUMJOBS=4 fio jobfile.fio
+
+.. code-block:: ini
+
+ ; -- start job file --
+ [random-writers]
+ rw=randwrite
+ size=${SIZE}
+ numjobs=${NUMJOBS}
+ ; -- end job file --
+
+This will expand to the following equivalent job file at runtime:
+
+.. code-block:: ini
+
+ ; -- start job file --
+ [random-writers]
+ rw=randwrite
+ size=64m
+ numjobs=4
+ ; -- end job file --
+
+Fio ships with a few example job files, you can also look there for inspiration.
+
+Reserved keywords
+~~~~~~~~~~~~~~~~~
+
+Additionally, fio has a set of reserved keywords that will be replaced
+internally with the appropriate value. Those keywords are:
+
+**$pagesize**
+
+ The architecture page size of the running system.
+
+**$mb_memory**
+
+ Megabytes of total memory in the system.
+
+**$ncpus**
+
+ Number of online available CPUs.
+
+These can be used on the command line or in the job file, and will be
+automatically substituted with the current system values when the job is
+run. Simple math is also supported on these keywords, so you can perform actions
+like::
+
+ size=8*$mb_memory
+
+and get that properly expanded to 8 times the size of memory in the machine.
+
+
+Job file parameters
+-------------------
+
+This section describes in details each parameter associated with a job. Some
+parameters take an option of a given type, such as an integer or a
+string. Anywhere a numeric value is required, an arithmetic expression may be
+used, provided it is surrounded by parentheses. Supported operators are:
+
+ - addition (+)
+ - subtraction (-)
+ - multiplication (*)
+ - division (/)
+ - modulus (%)
+ - exponentiation (^)
+
+For time values in expressions, units are microseconds by default. This is
+different than for time values not in expressions (not enclosed in
+parentheses). The following types are used:
+
+
+Parameter types
+~~~~~~~~~~~~~~~
+
+**str**
+ String: A sequence of alphanumeric characters.
+
+**time**
+ Integer with possible time suffix. Without a unit value is interpreted as
+ seconds unless otherwise specified. Accepts a suffix of 'd' for days, 'h' for
+ hours, 'm' for minutes, 's' for seconds, 'ms' (or 'msec') for milliseconds and
+ 'us' (or 'usec') for microseconds. For example, use 10m for 10 minutes.
+
+.. _int:
+
+**int**
+ Integer. A whole number value, which may contain an integer prefix
+ and an integer suffix:
+
+ [*integer prefix*] **number** [*integer suffix*]
+
+ The optional *integer prefix* specifies the number's base. The default
+ is decimal. *0x* specifies hexadecimal.
+
+ The optional *integer suffix* specifies the number's units, and includes an
+ optional unit prefix and an optional unit. For quantities of data, the
+ default unit is bytes. For quantities of time, the default unit is seconds
+ unless otherwise specified.
+
+ With :option:`kb_base`\=1000, fio follows international standards for unit
+ prefixes. To specify power-of-10 decimal values defined in the
+ International System of Units (SI):
+
+ * *K* -- means kilo (K) or 1000
+ * *M* -- means mega (M) or 1000**2
+ * *G* -- means giga (G) or 1000**3
+ * *T* -- means tera (T) or 1000**4
+ * *P* -- means peta (P) or 1000**5
+
+ To specify power-of-2 binary values defined in IEC 80000-13:
+
+ * *Ki* -- means kibi (Ki) or 1024
+ * *Mi* -- means mebi (Mi) or 1024**2
+ * *Gi* -- means gibi (Gi) or 1024**3
+ * *Ti* -- means tebi (Ti) or 1024**4
+ * *Pi* -- means pebi (Pi) or 1024**5
+
+ For Zone Block Device Mode:
+ * *z* -- means Zone
+
+ With :option:`kb_base`\=1024 (the default), the unit prefixes are opposite
+ from those specified in the SI and IEC 80000-13 standards to provide
+ compatibility with old scripts. For example, 4k means 4096.
+
+ For quantities of data, an optional unit of 'B' may be included
+ (e.g., 'kB' is the same as 'k').
+
+ The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega,
+ not milli). 'b' and 'B' both mean byte, not bit.
+
+ Examples with :option:`kb_base`\=1000:
+
+ * *4 KiB*: 4096, 4096b, 4096B, 4ki, 4kib, 4kiB, 4Ki, 4KiB
+ * *1 MiB*: 1048576, 1mi, 1024ki
+ * *1 MB*: 1000000, 1m, 1000k
+ * *1 TiB*: 1099511627776, 1ti, 1024gi, 1048576mi
+ * *1 TB*: 1000000000, 1t, 1000m, 1000000k
+
+ Examples with :option:`kb_base`\=1024 (default):
+
+ * *4 KiB*: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
+ * *1 MiB*: 1048576, 1m, 1024k
+ * *1 MB*: 1000000, 1mi, 1000ki
+ * *1 TiB*: 1099511627776, 1t, 1024g, 1048576m
+ * *1 TB*: 1000000000, 1ti, 1000mi, 1000000ki
+
+ To specify times (units are not case sensitive):
+
+ * *D* -- means days
+ * *H* -- means hours
+ * *M* -- means minutes
+ * *s* -- or sec means seconds (default)
+ * *ms* -- or *msec* means milliseconds
+ * *us* -- or *usec* means microseconds
+
+ If the option accepts an upper and lower range, use a colon ':' or
+ minus '-' to separate such values. See :ref:`irange <irange>`.
+ If the lower value specified happens to be larger than the upper value
+ the two values are swapped.
+
+.. _bool:
+
+**bool**
+ Boolean. Usually parsed as an integer, however only defined for
+ true and false (1 and 0).
+
+.. _irange:
+
+**irange**
+ Integer range with suffix. Allows value range to be given, such as
+ 1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the
+ option allows two sets of ranges, they can be specified with a ',' or '/'
+ delimiter: 1k-4k/8k-32k. Also see :ref:`int <int>`.
+
+**float_list**
+ A list of floating point numbers, separated by a ':' character.
+
+With the above in mind, here follows the complete list of fio job parameters.
+
+
+Units
+~~~~~
+
+.. option:: kb_base=int
+
+ Select the interpretation of unit prefixes in input parameters.
+
+ **1000**
+ Inputs comply with IEC 80000-13 and the International
+ System of Units (SI). Use:
+
+ - power-of-2 values with IEC prefixes (e.g., KiB)
+ - power-of-10 values with SI prefixes (e.g., kB)
+
+ **1024**
+ Compatibility mode (default). To avoid breaking old scripts:
+
+ - power-of-2 values with SI prefixes
+ - power-of-10 values with IEC prefixes
+
+ See :option:`bs` for more details on input parameters.
+
+ Outputs always use correct prefixes. Most outputs include both
+ side-by-side, like::
+
+ bw=2383.3kB/s (2327.4KiB/s)
+
+ If only one value is reported, then kb_base selects the one to use:
+
+ **1000** -- SI prefixes
+
+ **1024** -- IEC prefixes
+
+.. option:: unit_base=int
+
+ Base unit for reporting. Allowed values are:
+
+ **0**
+ Use auto-detection (default).
+ **8**
+ Byte based.
+ **1**
+ Bit based.
+
+
+Job description
+~~~~~~~~~~~~~~~
+
+.. option:: name=str
+
+ ASCII name of the job. This may be used to override the name printed by fio
+ for this job. Otherwise the job name is used. On the command line this
+ parameter has the special purpose of also signaling the start of a new job.
+
+.. option:: description=str
+
+ Text description of the job. Doesn't do anything except dump this text
+ description when this job is run. It's not parsed.
+
+.. option:: loops=int
+
+ Run the specified number of iterations of this job. Used to repeat the same
+ workload a given number of times. Defaults to 1.
+
+.. option:: numjobs=int
+
+ Create the specified number of clones of this job. Each clone of job
+ is spawned as an independent thread or process. May be used to setup a
+ larger number of threads/processes doing the same thing. Each thread is
+ reported separately; to see statistics for all clones as a whole, use
+ :option:`group_reporting` in conjunction with :option:`new_group`.
+ See :option:`--max-jobs`. Default: 1.
+
+
+Time related parameters
+~~~~~~~~~~~~~~~~~~~~~~~
+
+.. option:: runtime=time
+
+ Tell fio to terminate processing after the specified period of time. It
+ can be quite hard to determine for how long a specified job will run, so
+ this parameter is handy to cap the total runtime to a given time. When
+ the unit is omitted, the value is interpreted in seconds.
+
+.. option:: time_based
+
+ If set, fio will run for the duration of the :option:`runtime` specified
+ even if the file(s) are completely read or written. It will simply loop over
+ the same workload as many times as the :option:`runtime` allows.
+
+.. option:: startdelay=irange(time)
+
+ Delay the start of job for the specified amount of time. Can be a single
+ value or a range. When given as a range, each thread will choose a value
+ randomly from within the range. Value is in seconds if a unit is omitted.
+
+.. option:: ramp_time=time
+
+ If set, fio will run the specified workload for this amount of time before
+ logging any performance numbers. Useful for letting performance settle
+ before logging results, thus minimizing the runtime required for stable
+ results. Note that the ``ramp_time`` is considered lead in time for a job,
+ thus it will increase the total runtime if a special timeout or
+ :option:`runtime` is specified. When the unit is omitted, the value is
+ given in seconds.
+
+.. option:: clocksource=str
+
+ Use the given clocksource as the base of timing. The supported options are:
+
+ **gettimeofday**
+ :manpage:`gettimeofday(2)`
+
+ **clock_gettime**
+ :manpage:`clock_gettime(2)`
+
+ **cpu**
+ Internal CPU clock source
+
+ cpu is the preferred clocksource if it is reliable, as it is very fast (and
+ fio is heavy on time calls). Fio will automatically use this clocksource if
+ it's supported and considered reliable on the system it is running on,
+ unless another clocksource is specifically set. For x86/x86-64 CPUs, this
+ means supporting TSC Invariant.
+
+.. option:: gtod_reduce=bool
+
+ Enable all of the :manpage:`gettimeofday(2)` reducing options
+ (:option:`disable_clat`, :option:`disable_slat`, :option:`disable_bw_measurement`) plus
+ reduce precision of the timeout somewhat to really shrink the
+ :manpage:`gettimeofday(2)` call count. With this option enabled, we only do
+ about 0.4% of the :manpage:`gettimeofday(2)` calls we would have done if all
+ time keeping was enabled.
+
+.. option:: gtod_cpu=int
+
+ Sometimes it's cheaper to dedicate a single thread of execution to just
+ getting the current time. Fio (and databases, for instance) are very
+ intensive on :manpage:`gettimeofday(2)` calls. With this option, you can set
+ one CPU aside for doing nothing but logging current time to a shared memory
+ location. Then the other threads/processes that run I/O workloads need only
+ copy that segment, instead of entering the kernel with a
+ :manpage:`gettimeofday(2)` call. The CPU set aside for doing these time
+ calls will be excluded from other uses. Fio will manually clear it from the
+ CPU mask of other jobs.
+
+
+Target file/device
+~~~~~~~~~~~~~~~~~~
+
+.. option:: directory=str
+
+ Prefix filenames with this directory. Used to place files in a different
+ location than :file:`./`. You can specify a number of directories by
+ separating the names with a ':' character. These directories will be
+ assigned equally distributed to job clones created by :option:`numjobs` as
+ long as they are using generated filenames. If specific `filename(s)` are
+ set fio will use the first listed directory, and thereby matching the
+ `filename` semantic (which generates a file for each clone if not
+ specified, but lets all clones use the same file if set).
+
+ See the :option:`filename` option for information on how to escape "``:``"
+ characters within the directory path itself.
+
+ Note: To control the directory fio will use for internal state files
+ use :option:`--aux-path`.
+
+.. option:: filename=str
+
+ Fio normally makes up a `filename` based on the job name, thread number, and
+ file number (see :option:`filename_format`). If you want to share files
+ between threads in a job or several
+ jobs with fixed file paths, specify a `filename` for each of them to override
+ the default. If the ioengine is file based, you can specify a number of files
+ by separating the names with a ':' colon. So if you wanted a job to open
+ :file:`/dev/sda` and :file:`/dev/sdb` as the two working files, you would use
+ ``filename=/dev/sda:/dev/sdb``. This also means that whenever this option is
+ specified, :option:`nrfiles` is ignored. The size of regular files specified
+ by this option will be :option:`size` divided by number of files unless an
+ explicit size is specified by :option:`filesize`.
+
+ Each colon in the wanted path must be escaped with a ``\``
+ character. For instance, if the path is :file:`/dev/dsk/foo@3,0:c` then you
+ would use ``filename=/dev/dsk/foo@3,0\:c`` and if the path is
+ :file:`F:\\filename` then you would use ``filename=F\:\filename``.
+
+ On Windows, disk devices are accessed as :file:`\\\\.\\PhysicalDrive0` for
+ the first device, :file:`\\\\.\\PhysicalDrive1` for the second etc.
+ Note: Windows and FreeBSD prevent write access to areas
+ of the disk containing in-use data (e.g. filesystems).
+
+ The filename "`-`" is a reserved name, meaning *stdin* or *stdout*. Which
+ of the two depends on the read/write direction set.
+
+.. option:: filename_format=str
+
+ If sharing multiple files between jobs, it is usually necessary to have fio
+ generate the exact names that you want. By default, fio will name a file
+ based on the default file format specification of
+ :file:`jobname.jobnumber.filenumber`. With this option, that can be
+ customized. Fio will recognize and replace the following keywords in this
+ string:
+
+ **$jobname**
+ The name of the worker thread or process.
+ **$clientuid**
+ IP of the fio process when using client/server mode.
+ **$jobnum**
+ The incremental number of the worker thread or process.
+ **$filenum**
+ The incremental number of the file for that worker thread or
+ process.
+
+ To have dependent jobs share a set of files, this option can be set to have
+ fio generate filenames that are shared between the two. For instance, if
+ :file:`testfiles.$filenum` is specified, file number 4 for any job will be
+ named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
+ will be used if no other format specifier is given.
+
+ If you specify a path then the directories will be created up to the
+ main directory for the file. So for example if you specify
+ ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
+ created before the file setup part of the job. If you specify
+ :option:`directory` then the path will be relative that directory,
+ otherwise it is treated as the absolute path.
+
+.. option:: unique_filename=bool
+
+ To avoid collisions between networked clients, fio defaults to prefixing any
+ generated filenames (with a directory specified) with the source of the
+ client connecting. To disable this behavior, set this option to 0.
+
+.. option:: opendir=str
+
+ Recursively open any files below directory `str`.
+
+.. option:: lockfile=str
+
+ Fio defaults to not locking any files before it does I/O to them. If a file
+ or file descriptor is shared, fio can serialize I/O to that file to make the
+ end result consistent. This is usual for emulating real workloads that share
+ files. The lock modes are:
+
+ **none**
+ No locking. The default.
+ **exclusive**
+ Only one thread or process may do I/O at a time, excluding all
+ others.
+ **readwrite**
+ Read-write locking on the file. Many readers may
+ access the file at the same time, but writes get exclusive access.
+
+.. option:: nrfiles=int
+
+ Number of files to use for this job. Defaults to 1. The size of files
+ will be :option:`size` divided by this unless explicit size is specified by
+ :option:`filesize`. Files are created for each thread separately, and each
+ file will have a file number within its name by default, as explained in
+ :option:`filename` section.
+
+
+.. option:: openfiles=int
+
+ Number of files to keep open at the same time. Defaults to the same as
+ :option:`nrfiles`, can be set smaller to limit the number simultaneous
+ opens.
+
+.. option:: file_service_type=str
+
+ Defines how fio decides which file from a job to service next. The following
+ types are defined:
+
+ **random**
+ Choose a file at random.
+
+ **roundrobin**
+ Round robin over opened files. This is the default.
+
+ **sequential**
+ Finish one file before moving on to the next. Multiple files can
+ still be open depending on :option:`openfiles`.
+
+ **zipf**
+ Use a *Zipf* distribution to decide what file to access.
+
+ **pareto**
+ Use a *Pareto* distribution to decide what file to access.
+
+ **normal**
+ Use a *Gaussian* (normal) distribution to decide what file to
+ access.
+
+ **gauss**
+ Alias for normal.
+
+ For *random*, *roundrobin*, and *sequential*, a postfix can be appended to
+ tell fio how many I/Os to issue before switching to a new file. For example,
+ specifying ``file_service_type=random:8`` would cause fio to issue
+ 8 I/Os before selecting a new file at random. For the non-uniform
+ distributions, a floating point postfix can be given to influence how the
+ distribution is skewed. See :option:`random_distribution` for a description
+ of how that would work.
+
+.. option:: ioscheduler=str
+
+ Attempt to switch the device hosting the file to the specified I/O scheduler
+ before running.
+
+.. option:: create_serialize=bool
+
+ If true, serialize the file creation for the jobs. This may be handy to
+ avoid interleaving of data files, which may greatly depend on the filesystem
+ used and even the number of processors in the system. Default: true.
+
+.. option:: create_fsync=bool
+
+ :manpage:`fsync(2)` the data file after creation. This is the default.
+
+.. option:: create_on_open=bool
+
+ If true, don't pre-create files but allow the job's open() to create a file
+ when it's time to do I/O. Default: false -- pre-create all necessary files
+ when the job starts.
+
+.. option:: create_only=bool
+
+ If true, fio will only run the setup phase of the job. If files need to be
+ laid out or updated on disk, only that will be done -- the actual job contents
+ are not executed. Default: false.
+
+.. option:: allow_file_create=bool
+
+ If true, fio is permitted to create files as part of its workload. If this
+ option is false, then fio will error out if
+ the files it needs to use don't already exist. Default: true.
+
+.. option:: allow_mounted_write=bool
+
+ If this isn't set, fio will abort jobs that are destructive (e.g. that write)
+ to what appears to be a mounted device or partition. This should help catch
+ creating inadvertently destructive tests, not realizing that the test will
+ destroy data on the mounted file system. Note that some platforms don't allow
+ writing against a mounted device regardless of this option. Default: false.
+
+.. option:: pre_read=bool
+
+ If this is given, files will be pre-read into memory before starting the
+ given I/O operation. This will also clear the :option:`invalidate` flag,
+ since it is pointless to pre-read and then drop the cache. This will only
+ work for I/O engines that are seek-able, since they allow you to read the
+ same data multiple times. Thus it will not work on non-seekable I/O engines
+ (e.g. network, splice). Default: false.
+
+.. option:: unlink=bool
+
+ Unlink the job files when done. Not the default, as repeated runs of that
+ job would then waste time recreating the file set again and again. Default:
+ false.
+
+.. option:: unlink_each_loop=bool
+
+ Unlink job files after each iteration or loop. Default: false.
+
+.. option:: zonemode=str
+
+ Accepted values are:
+
+ **none**
+ The :option:`zonerange`, :option:`zonesize`,
+ :option `zonecapacity` and option:`zoneskip`
+ parameters are ignored.
+ **strided**
+ I/O happens in a single zone until
+ :option:`zonesize` bytes have been transferred.
+ After that number of bytes has been
+ transferred processing of the next zone
+ starts. :option `zonecapacity` is ignored.
+ **zbd**
+ Zoned block device mode. I/O happens
+ sequentially in each zone, even if random I/O
+ has been selected. Random I/O happens across
+ all zones instead of being restricted to a
+ single zone. The :option:`zoneskip` parameter
+ is ignored. :option:`zonerange` and
+ :option:`zonesize` must be identical.
+ Trim is handled using a zone reset operation.
+ Trim only considers non-empty sequential write
+ required and sequential write preferred zones.
+
+.. option:: zonerange=int
+
+ Size of a single zone. See also :option:`zonesize` and
+ :option:`zoneskip`.
+
+.. option:: zonesize=int
+
+ For :option:`zonemode` =strided, this is the number of bytes to
+ transfer before skipping :option:`zoneskip` bytes. If this parameter
+ is smaller than :option:`zonerange` then only a fraction of each zone
+ with :option:`zonerange` bytes will be accessed. If this parameter is
+ larger than :option:`zonerange` then each zone will be accessed
+ multiple times before skipping to the next zone.
+
+ For :option:`zonemode` =zbd, this is the size of a single zone. The
+ :option:`zonerange` parameter is ignored in this mode.
+
+
+.. option:: zonecapacity=int
+
+ For :option:`zonemode` =zbd, this defines the capacity of a single zone,
+ which is the accessible area starting from the zone start address.
+ This parameter only applies when using :option:`zonemode` =zbd in
+ combination with regular block devices. If not specified it defaults to
+ the zone size. If the target device is a zoned block device, the zone
+ capacity is obtained from the device information and this option is
+ ignored.
+
+.. option:: zoneskip=int
+
+ For :option:`zonemode` =strided, the number of bytes to skip after
+ :option:`zonesize` bytes of data have been transferred. This parameter
+ must be zero for :option:`zonemode` =zbd.
+
+.. option:: read_beyond_wp=bool
+
+ This parameter applies to :option:`zonemode` =zbd only.
+
+ Zoned block devices are block devices that consist of multiple zones.
+ Each zone has a type, e.g. conventional or sequential. A conventional
+ zone can be written at any offset that is a multiple of the block
+ size. Sequential zones must be written sequentially. The position at
+ which a write must occur is called the write pointer. A zoned block
+ device can be either drive managed, host managed or host aware. For
+ host managed devices the host must ensure that writes happen
+ sequentially. Fio recognizes host managed devices and serializes
+ writes to sequential zones for these devices.
+
+ If a read occurs in a sequential zone beyond the write pointer then
+ the zoned block device will complete the read without reading any data
+ from the storage medium. Since such reads lead to unrealistically high
+ bandwidth and IOPS numbers fio only reads beyond the write pointer if
+ explicitly told to do so. Default: false.
+
+.. option:: max_open_zones=int
+
+ When running a random write test across an entire drive many more
+ zones will be open than in a typical application workload. Hence this
+ command line option that allows to limit the number of open zones. The
+ number of open zones is defined as the number of zones to which write
+ commands are issued.
+
+.. option:: job_max_open_zones=int
+
+ Limit on the number of simultaneously opened zones per single
+ thread/process.
+
+.. option:: ignore_zone_limits=bool
+ If this option is used, fio will ignore the maximum number of open
+ zones limit of the zoned block device in use, thus allowing the
+ option :option:`max_open_zones` value to be larger than the device
+ reported limit. Default: false.
+
+.. option:: zone_reset_threshold=float
+
+ A number between zero and one that indicates the ratio of logical
+ blocks with data to the total number of logical blocks in the test
+ above which zones should be reset periodically.
+
+.. option:: zone_reset_frequency=float
+
+ A number between zero and one that indicates how often a zone reset
+ should be issued if the zone reset threshold has been exceeded. A zone
+ reset is submitted after each (1 / zone_reset_frequency) write
+ requests. This and the previous parameter can be used to simulate
+ garbage collection activity.
+
+
+I/O type
+~~~~~~~~
+
+.. option:: direct=bool
+
+ If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that
+ OpenBSD and ZFS on Solaris don't support direct I/O. On Windows the synchronous
+ ioengines don't support direct I/O. Default: false.
+
+.. option:: atomic=bool
+
+ If value is true, attempt to use atomic direct I/O. Atomic writes are
+ guaranteed to be stable once acknowledged by the operating system. Only
+ Linux supports O_ATOMIC right now.
+
+.. option:: buffered=bool
+
+ If value is true, use buffered I/O. This is the opposite of the
+ :option:`direct` option. Defaults to true.
+
+.. option:: readwrite=str, rw=str
+
+ Type of I/O pattern. Accepted values are:
+
+ **read**
+ Sequential reads.
+ **write**
+ Sequential writes.
+ **trim**
+ Sequential trims (Linux block devices and SCSI
+ character devices only).
+ **randread**
+ Random reads.
+ **randwrite**
+ Random writes.
+ **randtrim**
+ Random trims (Linux block devices and SCSI
+ character devices only).
+ **rw,readwrite**
+ Sequential mixed reads and writes.
+ **randrw**
+ Random mixed reads and writes.
+ **trimwrite**
+ Sequential trim+write sequences. Blocks will be trimmed first,
+ then the same blocks will be written to.
+
+ Fio defaults to read if the option is not specified. For the mixed I/O
+ types, the default is to split them 50/50. For certain types of I/O the
+ result may still be skewed a bit, since the speed may be different.
+
+ It is possible to specify the number of I/Os to do before getting a new
+ offset by appending ``:<nr>`` to the end of the string given. For a
+ random read, it would look like ``rw=randread:8`` for passing in an offset
+ modifier with a value of 8. If the suffix is used with a sequential I/O
+ pattern, then the *<nr>* value specified will be **added** to the generated
+ offset for each I/O turning sequential I/O into sequential I/O with holes.
+ For instance, using ``rw=write:4k`` will skip 4k for every write. Also see
+ the :option:`rw_sequencer` option.
+
+.. option:: rw_sequencer=str
+
+ If an offset modifier is given by appending a number to the ``rw=<str>``
+ line, then this option controls how that number modifies the I/O offset
+ being generated. Accepted values are:
+
+ **sequential**
+ Generate sequential offset.
+ **identical**
+ Generate the same offset.
+
+ ``sequential`` is only useful for random I/O, where fio would normally
+ generate a new random offset for every I/O. If you append e.g. 8 to randread,
+ you would get a new random offset for every 8 I/Os. The result would be a
+ seek for only every 8 I/Os, instead of for every I/O. Use ``rw=randread:8``
+ to specify that. As sequential I/O is already sequential, setting
+ ``sequential`` for that would not result in any differences. ``identical``
+ behaves in a similar fashion, except it sends the same offset 8 number of
+ times before generating a new offset.
+
+.. option:: unified_rw_reporting=str
+
+ Fio normally reports statistics on a per data direction basis, meaning that
+ reads, writes, and trims are accounted and reported separately. This option
+ determines whether fio reports the results normally, summed together, or as
+ both options.
+ Accepted values are:
+
+ **none**
+ Normal statistics reporting.
+
+ **mixed**
+ Statistics are summed per data direction and reported together.
+
+ **both**
+ Statistics are reported normally, followed by the mixed statistics.
+
+ **0**
+ Backward-compatible alias for **none**.
+
+ **1**
+ Backward-compatible alias for **mixed**.
+
+ **2**
+ Alias for **both**.
+
+.. option:: randrepeat=bool
+
+ Seed the random number generator used for random I/O patterns in a
+ predictable way so the pattern is repeatable across runs. Default: true.
+
+.. option:: allrandrepeat=bool
+
+ Seed all random number generators in a predictable way so results are
+ repeatable across runs. Default: false.
+
+.. option:: randseed=int
+
+ Seed the random number generators based on this seed value, to be able to
+ control what sequence of output is being generated. If not set, the random
+ sequence depends on the :option:`randrepeat` setting.
+
+.. option:: fallocate=str
+
+ Whether pre-allocation is performed when laying down files.
+ Accepted values are:
+
+ **none**
+ Do not pre-allocate space.
+
+ **native**
+ Use a platform's native pre-allocation call but fall back to
+ **none** behavior if it fails/is not implemented.
+
+ **posix**
+ Pre-allocate via :manpage:`posix_fallocate(3)`.
+
+ **keep**
+ Pre-allocate via :manpage:`fallocate(2)` with
+ FALLOC_FL_KEEP_SIZE set.
+
+ **truncate**
+ Extend file to final size via :manpage:`ftruncate(2)`
+ instead of allocating.
+
+ **0**
+ Backward-compatible alias for **none**.
+
+ **1**
+ Backward-compatible alias for **posix**.
+
+ May not be available on all supported platforms. **keep** is only available
+ on Linux. If using ZFS on Solaris this cannot be set to **posix**
+ because ZFS doesn't support pre-allocation. Default: **native** if any
+ pre-allocation methods except **truncate** are available, **none** if not.
+
+ Note that using **truncate** on Windows will interact surprisingly
+ with non-sequential write patterns. When writing to a file that has
+ been extended by setting the end-of-file information, Windows will
+ backfill the unwritten portion of the file up to that offset with
+ zeroes before issuing the new write. This means that a single small
+ write to the end of an extended file will stall until the entire
+ file has been filled with zeroes.
+
+.. option:: fadvise_hint=str
+
+ Use :manpage:`posix_fadvise(2)` or :manpage:`posix_fadvise(2)` to
+ advise the kernel on what I/O patterns are likely to be issued.
+ Accepted values are:
+
+ **0**
+ Backwards-compatible hint for "no hint".
+
+ **1**
+ Backwards compatible hint for "advise with fio workload type". This
+ uses **FADV_RANDOM** for a random workload, and **FADV_SEQUENTIAL**
+ for a sequential workload.
+
+ **sequential**
+ Advise using **FADV_SEQUENTIAL**.
+
+ **random**
+ Advise using **FADV_RANDOM**.
+
+.. option:: write_hint=str
+
+ Use :manpage:`fcntl(2)` to advise the kernel what life time to expect
+ from a write. Only supported on Linux, as of version 4.13. Accepted
+ values are:
+
+ **none**
+ No particular life time associated with this file.
+
+ **short**
+ Data written to this file has a short life time.
+
+ **medium**
+ Data written to this file has a medium life time.
+
+ **long**
+ Data written to this file has a long life time.
+
+ **extreme**
+ Data written to this file has a very long life time.
+
+ The values are all relative to each other, and no absolute meaning
+ should be associated with them.
+
+.. option:: offset=int
+
+ Start I/O at the provided offset in the file, given as either a fixed size in
+ bytes, zones or a percentage. If a percentage is given, the generated offset will be
+ aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
+ provided. Data before the given offset will not be touched. This
+ effectively caps the file size at `real_size - offset`. Can be combined with
+ :option:`size` to constrain the start and end range of the I/O workload.
+ A percentage can be specified by a number between 1 and 100 followed by '%',
+ for example, ``offset=20%`` to specify 20%. In ZBD mode, value can be set as
+ number of zones using 'z'.
+
+.. option:: offset_align=int
+
+ If set to non-zero value, the byte offset generated by a percentage ``offset``
+ is aligned upwards to this value. Defaults to 0 meaning that a percentage
+ offset is aligned to the minimum block size.
+
+.. option:: offset_increment=int
+
+ If this is provided, then the real offset becomes `offset + offset_increment
+ * thread_number`, where the thread number is a counter that starts at 0 and
+ is incremented for each sub-job (i.e. when :option:`numjobs` option is
+ specified). This option is useful if there are several jobs which are
+ intended to operate on a file in parallel disjoint segments, with even
+ spacing between the starting points. Percentages can be used for this option.
+ If a percentage is given, the generated offset will be aligned to the minimum
+ ``blocksize`` or to the value of ``offset_align`` if provided. In ZBD mode, value can
+ also be set as number of zones using 'z'.
+
+.. option:: number_ios=int
+
+ Fio will normally perform I/Os until it has exhausted the size of the region
+ set by :option:`size`, or if it exhaust the allocated time (or hits an error
+ condition). With this setting, the range/size can be set independently of
+ the number of I/Os to perform. When fio reaches this number, it will exit
+ normally and report status. Note that this does not extend the amount of I/O
+ that will be done, it will only stop fio if this condition is met before
+ other end-of-job criteria.
+
+.. option:: fsync=int
+
+ If writing to a file, issue an :manpage:`fsync(2)` (or its equivalent) of
+ the dirty data for every number of blocks given. For example, if you give 32
+ as a parameter, fio will sync the file after every 32 writes issued. If fio is
+ using non-buffered I/O, we may not sync the file. The exception is the sg
+ I/O engine, which synchronizes the disk cache anyway. Defaults to 0, which
+ means fio does not periodically issue and wait for a sync to complete. Also
+ see :option:`end_fsync` and :option:`fsync_on_close`.
+
+.. option:: fdatasync=int
+
+ Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and
+ not metadata blocks. In Windows, DragonFlyBSD or OSX there is no
+ :manpage:`fdatasync(2)` so this falls back to using :manpage:`fsync(2)`.
+ Defaults to 0, which means fio does not periodically issue and wait for a
+ data-only sync to complete.
+
+.. option:: write_barrier=int
+
+ Make every `N-th` write a barrier write.
+
+.. option:: sync_file_range=str:int
+
+ Use :manpage:`sync_file_range(2)` for every `int` number of write
+ operations. Fio will track range of writes that have happened since the last
+ :manpage:`sync_file_range(2)` call. `str` can currently be one or more of:
+
+ **wait_before**
+ SYNC_FILE_RANGE_WAIT_BEFORE
+ **write**
+ SYNC_FILE_RANGE_WRITE
+ **wait_after**
+ SYNC_FILE_RANGE_WAIT_AFTER
+
+ So if you do ``sync_file_range=wait_before,write:8``, fio would use
+ ``SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE`` for every 8
+ writes. Also see the :manpage:`sync_file_range(2)` man page. This option is
+ Linux specific.
+
+.. option:: overwrite=bool
+
+ If true, writes to a file will always overwrite existing data. If the file
+ doesn't already exist, it will be created before the write phase begins. If
+ the file exists and is large enough for the specified write phase, nothing
+ will be done. Default: false.
+
+.. option:: end_fsync=bool
+
+ If true, :manpage:`fsync(2)` file contents when a write stage has completed.
+ Default: false.
+
+.. option:: fsync_on_close=bool
+
+ If true, fio will :manpage:`fsync(2)` a dirty file on close. This differs
+ from :option:`end_fsync` in that it will happen on every file close, not
+ just at the end of the job. Default: false.
+
+.. option:: rwmixread=int
+
+ Percentage of a mixed workload that should be reads. Default: 50.
+
+.. option:: rwmixwrite=int
+
+ Percentage of a mixed workload that should be writes. If both
+ :option:`rwmixread` and :option:`rwmixwrite` is given and the values do not
+ add up to 100%, the latter of the two will be used to override the
+ first. This may interfere with a given rate setting, if fio is asked to
+ limit reads or writes to a certain rate. If that is the case, then the
+ distribution may be skewed. Default: 50.
+
+.. option:: random_distribution=str:float[:float][,str:float][,str:float]
+
+ By default, fio will use a completely uniform random distribution when asked
+ to perform random I/O. Sometimes it is useful to skew the distribution in
+ specific ways, ensuring that some parts of the data is more hot than others.
+ fio includes the following distribution models:
+
+ **random**
+ Uniform random distribution
+
+ **zipf**
+ Zipf distribution
+
+ **pareto**
+ Pareto distribution
+
+ **normal**
+ Normal (Gaussian) distribution
+
+ **zoned**
+ Zoned random distribution
+
+ **zoned_abs**
+ Zone absolute random distribution
+
+ When using a **zipf** or **pareto** distribution, an input value is also
+ needed to define the access pattern. For **zipf**, this is the `Zipf
+ theta`. For **pareto**, it's the `Pareto power`. Fio includes a test
+ program, :command:`fio-genzipf`, that can be used visualize what the given input
+ values will yield in terms of hit rates. If you wanted to use **zipf** with
+ a `theta` of 1.2, you would use ``random_distribution=zipf:1.2`` as the
+ option. If a non-uniform model is used, fio will disable use of the random
+ map. For the **normal** distribution, a normal (Gaussian) deviation is
+ supplied as a value between 0 and 100.
+
+ The second, optional float is allowed for **pareto**, **zipf** and **normal** distributions.
+ It allows to set base of distribution in non-default place, giving more control
+ over most probable outcome. This value is in range [0-1] which maps linearly to
+ range of possible random values.
+ Defaults are: random for **pareto** and **zipf**, and 0.5 for **normal**.
+ If you wanted to use **zipf** with a `theta` of 1.2 centered on 1/4 of allowed value range,
+ you would use ``random_distibution=zipf:1.2:0.25``.
+
+ For a **zoned** distribution, fio supports specifying percentages of I/O
+ access that should fall within what range of the file or device. For
+ example, given a criteria of:
+
+ * 60% of accesses should be to the first 10%
+ * 30% of accesses should be to the next 20%
+ * 8% of accesses should be to the next 30%
+ * 2% of accesses should be to the next 40%
+
+ we can define that through zoning of the random accesses. For the above
+ example, the user would do::
+
+ random_distribution=zoned:60/10:30/20:8/30:2/40
+
+ A **zoned_abs** distribution works exactly like the **zoned**, except
+ that it takes absolute sizes. For example, let's say you wanted to
+ define access according to the following criteria:
+
+ * 60% of accesses should be to the first 20G
+ * 30% of accesses should be to the next 100G
+ * 10% of accesses should be to the next 500G
+
+ we can define an absolute zoning distribution with:
+
+ random_distribution=zoned_abs=60/20G:30/100G:10/500g
+
+ For both **zoned** and **zoned_abs**, fio supports defining up to
+ 256 separate zones.
+
+ Similarly to how :option:`bssplit` works for setting ranges and
+ percentages of block sizes. Like :option:`bssplit`, it's possible to
+ specify separate zones for reads, writes, and trims. If just one set
+ is given, it'll apply to all of them. This goes for both **zoned**
+ **zoned_abs** distributions.
+
+.. option:: percentage_random=int[,int][,int]
+
+ For a random workload, set how big a percentage should be random. This
+ defaults to 100%, in which case the workload is fully random. It can be set
+ from anywhere from 0 to 100. Setting it to 0 would make the workload fully
+ sequential. Any setting in between will result in a random mix of sequential
+ and random I/O, at the given percentages. Comma-separated values may be
+ specified for reads, writes, and trims as described in :option:`blocksize`.
+
+.. option:: norandommap
+
+ Normally fio will cover every block of the file when doing random I/O. If
+ this option is given, fio will just get a new random offset without looking
+ at past I/O history. This means that some blocks may not be read or written,
+ and that some blocks may be read/written more than once. If this option is
+ used with :option:`verify` and multiple blocksizes (via :option:`bsrange`),
+ only intact blocks are verified, i.e., partially-overwritten blocks are
+ ignored. With an async I/O engine and an I/O depth > 1, it is possible for
+ the same block to be overwritten, which can cause verification errors. Either
+ do not use norandommap in this case, or also use the lfsr random generator.
+
+.. option:: softrandommap=bool
+
+ See :option:`norandommap`. If fio runs with the random block map enabled and
+ it fails to allocate the map, if this option is set it will continue without
+ a random block map. As coverage will not be as complete as with random maps,
+ this option is disabled by default.
+
+.. option:: random_generator=str
+
+ Fio supports the following engines for generating I/O offsets for random I/O:
+
+ **tausworthe**
+ Strong 2^88 cycle random number generator.
+ **lfsr**
+ Linear feedback shift register generator.
+ **tausworthe64**
+ Strong 64-bit 2^258 cycle random number generator.
+
+ **tausworthe** is a strong random number generator, but it requires tracking
+ on the side if we want to ensure that blocks are only read or written
+ once. **lfsr** guarantees that we never generate the same offset twice, and
+ it's also less computationally expensive. It's not a true random generator,
+ however, though for I/O purposes it's typically good enough. **lfsr** only
+ works with single block sizes, not with workloads that use multiple block
+ sizes. If used with such a workload, fio may read or write some blocks
+ multiple times. The default value is **tausworthe**, unless the required
+ space exceeds 2^32 blocks. If it does, then **tausworthe64** is
+ selected automatically.
+
+
+Block size
+~~~~~~~~~~
+
+.. option:: blocksize=int[,int][,int], bs=int[,int][,int]
+
+ The block size in bytes used for I/O units. Default: 4096. A single value
+ applies to reads, writes, and trims. Comma-separated values may be
+ specified for reads, writes, and trims. A value not terminated in a comma
+ applies to subsequent types.
+
+ Examples:
+
+ **bs=256k**
+ means 256k for reads, writes and trims.
+
+ **bs=8k,32k**
+ means 8k for reads, 32k for writes and trims.
+
+ **bs=8k,32k,**
+ means 8k for reads, 32k for writes, and default for trims.
+
+ **bs=,8k**
+ means default for reads, 8k for writes and trims.
+
+ **bs=,8k,**
+ means default for reads, 8k for writes, and default for trims.
+
+.. option:: blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
+
+ A range of block sizes in bytes for I/O units. The issued I/O unit will
+ always be a multiple of the minimum size, unless
+ :option:`blocksize_unaligned` is set.
+
+ Comma-separated ranges may be specified for reads, writes, and trims as
+ described in :option:`blocksize`.
+
+ Example: ``bsrange=1k-4k,2k-8k``.
+
+.. option:: bssplit=str[,str][,str]
+
+ Sometimes you want even finer grained control of the block sizes
+ issued, not just an even split between them. This option allows you to
+ weight various block sizes, so that you are able to define a specific
+ amount of block sizes issued. The format for this option is::
+
+ bssplit=blocksize/percentage:blocksize/percentage
+
+ for as many block sizes as needed. So if you want to define a workload
+ that has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you would
+ write::
+
+ bssplit=4k/10:64k/50:32k/40
+
+ Ordering does not matter. If the percentage is left blank, fio will
+ fill in the remaining values evenly. So a bssplit option like this one::
+
+ bssplit=4k/50:1k/:32k/
+
+ would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always
+ add up to 100, if bssplit is given a range that adds up to more, it
+ will error out.
+
+ Comma-separated values may be specified for reads, writes, and trims as
+ described in :option:`blocksize`.
+
+ If you want a workload that has 50% 2k reads and 50% 4k reads, while
+ having 90% 4k writes and 10% 8k writes, you would specify::
+
+ bssplit=2k/50:4k/50,4k/90:8k/10
+
+ Fio supports defining up to 64 different weights for each data
+ direction.
+
+.. option:: blocksize_unaligned, bs_unaligned
+
+ If set, fio will issue I/O units with any size within
+ :option:`blocksize_range`, not just multiples of the minimum size. This
+ typically won't work with direct I/O, as that normally requires sector
+ alignment.
+
+.. option:: bs_is_seq_rand=bool
+
+ If this option is set, fio will use the normal read,write blocksize settings
+ as sequential,random blocksize settings instead. Any random read or write
+ will use the WRITE blocksize settings, and any sequential read or write will
+ use the READ blocksize settings.
+
+.. option:: blockalign=int[,int][,int], ba=int[,int][,int]
+
+ Boundary to which fio will align random I/O units. Default:
+ :option:`blocksize`. Minimum alignment is typically 512b for using direct
+ I/O, though it usually depends on the hardware block size. This option is
+ mutually exclusive with using a random map for files, so it will turn off
+ that option. Comma-separated values may be specified for reads, writes, and
+ trims as described in :option:`blocksize`.
+
+
+Buffers and memory
+~~~~~~~~~~~~~~~~~~
+
+.. option:: zero_buffers
+
+ Initialize buffers with all zeros. Default: fill buffers with random data.
+
+.. option:: refill_buffers
+
+ If this option is given, fio will refill the I/O buffers on every
+ submit. Only makes sense if :option:`zero_buffers` isn't specified,
+ naturally. Defaults to being unset i.e., the buffer is only filled at
+ init time and the data in it is reused when possible but if any of
+ :option:`verify`, :option:`buffer_compress_percentage` or
+ :option:`dedupe_percentage` are enabled then `refill_buffers` is also
+ automatically enabled.
+
+.. option:: scramble_buffers=bool
+
+ If :option:`refill_buffers` is too costly and the target is using data
+ deduplication, then setting this option will slightly modify the I/O buffer
+ contents to defeat normal de-dupe attempts. This is not enough to defeat
+ more clever block compression attempts, but it will stop naive dedupe of
+ blocks. Default: true.
+
+.. option:: buffer_compress_percentage=int
+
+ If this is set, then fio will attempt to provide I/O buffer content
+ (on WRITEs) that compresses to the specified level. Fio does this by
+ providing a mix of random data followed by fixed pattern data. The
+ fixed pattern is either zeros, or the pattern specified by
+ :option:`buffer_pattern`. If the `buffer_pattern` option is used, it
+ might skew the compression ratio slightly. Setting
+ `buffer_compress_percentage` to a value other than 100 will also
+ enable :option:`refill_buffers` in order to reduce the likelihood that
+ adjacent blocks are so similar that they over compress when seen
+ together. See :option:`buffer_compress_chunk` for how to set a finer or
+ coarser granularity for the random/fixed data region. Defaults to unset
+ i.e., buffer data will not adhere to any compression level.
+
+.. option:: buffer_compress_chunk=int
+
+ This setting allows fio to manage how big the random/fixed data region
+ is when using :option:`buffer_compress_percentage`. When
+ `buffer_compress_chunk` is set to some non-zero value smaller than the
+ block size, fio can repeat the random/fixed region throughout the I/O
+ buffer at the specified interval (which particularly useful when
+ bigger block sizes are used for a job). When set to 0, fio will use a
+ chunk size that matches the block size resulting in a single
+ random/fixed region within the I/O buffer. Defaults to 512. When the
+ unit is omitted, the value is interpreted in bytes.
+
+.. option:: buffer_pattern=str
+
+ If set, fio will fill the I/O buffers with this pattern or with the contents
+ of a file. If not set, the contents of I/O buffers are defined by the other
+ options related to buffer contents. The setting can be any pattern of bytes,
+ and can be prefixed with 0x for hex values. It may also be a string, where
+ the string must then be wrapped with ``""``. Or it may also be a filename,
+ where the filename must be wrapped with ``''`` in which case the file is
+ opened and read. Note that not all the file contents will be read if that
+ would cause the buffers to overflow. So, for example::
+
+ buffer_pattern='filename'
+
+ or::
+
+ buffer_pattern="abcd"
+
+ or::
+
+ buffer_pattern=-12
+
+ or::
+
+ buffer_pattern=0xdeadface
+
+ Also you can combine everything together in any order::
+
+ buffer_pattern=0xdeadface"abcd"-12'filename'
+
+.. option:: dedupe_percentage=int
+
+ If set, fio will generate this percentage of identical buffers when
+ writing. These buffers will be naturally dedupable. The contents of the
+ buffers depend on what other buffer compression settings have been set. It's
+ possible to have the individual buffers either fully compressible, or not at
+ all -- this option only controls the distribution of unique buffers. Setting
+ this option will also enable :option:`refill_buffers` to prevent every buffer
+ being identical.
+
+.. option:: dedupe_mode=str
+
+ If ``dedupe_percentage=<int>`` is given, then this option controls how fio
+ generates the dedupe buffers.
+
+ **repeat**
+ Generate dedupe buffers by repeating previous writes
+ **working_set**
+ Generate dedupe buffers from working set
+
+ ``repeat`` is the default option for fio. Dedupe buffers are generated
+ by repeating previous unique write.
+
+ ``working_set`` is a more realistic workload.
+ With ``working_set``, ``dedupe_working_set_percentage=<int>`` should be provided.
+ Given that, fio will use the initial unique write buffers as its working set.
+ Upon deciding to dedupe, fio will randomly choose a buffer from the working set.
+ Note that by using ``working_set`` the dedupe percentage will converge
+ to the desired over time while ``repeat`` maintains the desired percentage
+ throughout the job.
+
+.. option:: dedupe_working_set_percentage=int
+
+ If ``dedupe_mode=<str>`` is set to ``working_set``, then this controls
+ the percentage of size of the file or device used as the buffers
+ fio will choose to generate the dedupe buffers from
+
+ Note that size needs to be explicitly provided and only 1 file per
+ job is supported
+
+.. option:: invalidate=bool
+
+ Invalidate the buffer/page cache parts of the files to be used prior to
+ starting I/O if the platform and file type support it. Defaults to true.
+ This will be ignored if :option:`pre_read` is also specified for the
+ same job.
+
+.. option:: sync=str
+
+ Whether, and what type, of synchronous I/O to use for writes. The allowed
+ values are:
+
+ **none**
+ Do not use synchronous IO, the default.
+
+ **0**
+ Same as **none**.
+
+ **sync**
+ Use synchronous file IO. For the majority of I/O engines,
+ this means using O_SYNC.
+
+ **1**
+ Same as **sync**.
+
+ **dsync**
+ Use synchronous data IO. For the majority of I/O engines,
+ this means using O_DSYNC.
+
+
+.. option:: iomem=str, mem=str
+
+ Fio can use various types of memory as the I/O unit buffer. The allowed
+ values are:
+
+ **malloc**
+ Use memory from :manpage:`malloc(3)` as the buffers. Default memory
+ type.
+
+ **shm**
+ Use shared memory as the buffers. Allocated through
+ :manpage:`shmget(2)`.
+
+ **shmhuge**
+ Same as shm, but use huge pages as backing.
+
+ **mmap**
+ Use :manpage:`mmap(2)` to allocate buffers. May either be anonymous memory, or can
+ be file backed if a filename is given after the option. The format
+ is `mem=mmap:/path/to/file`.
+
+ **mmaphuge**
+ Use a memory mapped huge file as the buffer backing. Append filename
+ after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file`.
+
+ **mmapshared**
+ Same as mmap, but use a MMAP_SHARED mapping.
+
+ **cudamalloc**
+ Use GPU memory as the buffers for GPUDirect RDMA benchmark.
+ The :option:`ioengine` must be `rdma`.
+
+ The area allocated is a function of the maximum allowed bs size for the job,
+ multiplied by the I/O depth given. Note that for **shmhuge** and
+ **mmaphuge** to work, the system must have free huge pages allocated. This
+ can normally be checked and set by reading/writing
+ :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page
+ is 4MiB in size. So to calculate the number of huge pages you need for a
+ given job file, add up the I/O depth of all jobs (normally one unless
+ :option:`iodepth` is used) and multiply by the maximum bs set. Then divide
+ that number by the huge page size. You can see the size of the huge pages in
+ :file:`/proc/meminfo`. If no huge pages are allocated by having a non-zero
+ number in `nr_hugepages`, using **mmaphuge** or **shmhuge** will fail. Also
+ see :option:`hugepage-size`.
+
+ **mmaphuge** also needs to have hugetlbfs mounted and the file location
+ should point there. So if it's mounted in :file:`/huge`, you would use
+ `mem=mmaphuge:/huge/somefile`.
+
+.. option:: iomem_align=int, mem_align=int
+
+ This indicates the memory alignment of the I/O memory buffers. Note that
+ the given alignment is applied to the first I/O unit buffer, if using
+ :option:`iodepth` the alignment of the following buffers are given by the
+ :option:`bs` used. In other words, if using a :option:`bs` that is a
+ multiple of the page sized in the system, all buffers will be aligned to
+ this value. If using a :option:`bs` that is not page aligned, the alignment
+ of subsequent I/O memory buffers is the sum of the :option:`iomem_align` and
+ :option:`bs` used.
+
+.. option:: hugepage-size=int
+
+ Defines the size of a huge page. Must at least be equal to the system
+ setting, see :file:`/proc/meminfo`. Defaults to 4MiB. Should probably
+ always be a multiple of megabytes, so using ``hugepage-size=Xm`` is the
+ preferred way to set this to avoid setting a non-pow-2 bad value.
+
+.. option:: lockmem=int
+
+ Pin the specified amount of memory with :manpage:`mlock(2)`. Can be used to
+ simulate a smaller amount of memory. The amount specified is per worker.
+
+
+I/O size
+~~~~~~~~
+
+.. option:: size=int
+
+ The total size of file I/O for each thread of this job. Fio will run until
+ this many bytes has been transferred, unless runtime is limited by other options
+ (such as :option:`runtime`, for instance, or increased/decreased by :option:`io_size`).
+ Fio will divide this size between the available files determined by options
+ such as :option:`nrfiles`, :option:`filename`, unless :option:`filesize` is
+ specified by the job. If the result of division happens to be 0, the size is
+ set to the physical size of the given files or devices if they exist.
+ If this option is not specified, fio will use the full size of the given
+ files or devices. If the files do not exist, size must be given. It is also
+ possible to give size as a percentage between 1 and 100. If ``size=20%`` is
+ given, fio will use 20% of the full size of the given files or devices.
+ In ZBD mode, value can also be set as number of zones using 'z'.
+ Can be combined with :option:`offset` to constrain the start and end range
+ that I/O will be done within.
+
+.. option:: io_size=int, io_limit=int
+
+ Normally fio operates within the region set by :option:`size`, which means
+ that the :option:`size` option sets both the region and size of I/O to be
+ performed. Sometimes that is not what you want. With this option, it is
+ possible to define just the amount of I/O that fio should do. For instance,
+ if :option:`size` is set to 20GiB and :option:`io_size` is set to 5GiB, fio
+ will perform I/O within the first 20GiB but exit when 5GiB have been
+ done. The opposite is also possible -- if :option:`size` is set to 20GiB,
+ and :option:`io_size` is set to 40GiB, then fio will do 40GiB of I/O within
+ the 0..20GiB region.
+
+.. option:: filesize=irange(int)
+
+ Individual file sizes. May be a range, in which case fio will select sizes for
+ files at random within the given range. If not given, each created file is the
+ same size. This option overrides :option:`size` in terms of file size, i.e. if
+ :option:`filesize` is specified then :option:`size` becomes merely the default
+ for :option:`io_size` and has no effect at all if :option:`io_size` is set
+ explicitly.
+
+.. option:: file_append=bool
+
+ Perform I/O after the end of the file. Normally fio will operate within the
+ size of a file. If this option is set, then fio will append to the file
+ instead. This has identical behavior to setting :option:`offset` to the size
+ of a file. This option is ignored on non-regular files.
+
+.. option:: fill_device=bool, fill_fs=bool
+
+ Sets size to something really large and waits for ENOSPC (no space left on
+ device) or EDQUOT (disk quota exceeded)
+ as the terminating condition. Only makes sense with sequential
+ write. For a read workload, the mount point will be filled first then I/O
+ started on the result. This option doesn't make sense if operating on a raw
+ device node, since the size of that is already known by the file system.
+ Additionally, writing beyond end-of-device will not return ENOSPC there.
+
+
+I/O engine
+~~~~~~~~~~
+
+.. option:: ioengine=str
+
+ Defines how the job issues I/O to the file. The following types are defined:
+
+ **sync**
+ Basic :manpage:`read(2)` or :manpage:`write(2)`
+ I/O. :manpage:`lseek(2)` is used to position the I/O location.
+ See :option:`fsync` and :option:`fdatasync` for syncing write I/Os.
+
+ **psync**
+ Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O. Default on
+ all supported operating systems except for Windows.
+
+ **vsync**
+ Basic :manpage:`readv(2)` or :manpage:`writev(2)` I/O. Will emulate
+ queuing by coalescing adjacent I/Os into a single submission.
+
+ **pvsync**
+ Basic :manpage:`preadv(2)` or :manpage:`pwritev(2)` I/O.
+
+ **pvsync2**
+ Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O.
+
+ **io_uring**
+ Fast Linux native asynchronous I/O. Supports async IO
+ for both direct and buffered IO.
+ This engine defines engine specific options.
+
+ **libaio**
+ Linux native asynchronous I/O. Note that Linux may only support
+ queued behavior with non-buffered I/O (set ``direct=1`` or
+ ``buffered=0``).
+ This engine defines engine specific options.
+
+ **posixaio**
+ POSIX asynchronous I/O using :manpage:`aio_read(3)` and
+ :manpage:`aio_write(3)`.
+
+ **solarisaio**
+ Solaris native asynchronous I/O.
+
+ **windowsaio**
+ Windows native asynchronous I/O. Default on Windows.
+
+ **mmap**
+ File is memory mapped with :manpage:`mmap(2)` and data copied
+ to/from using :manpage:`memcpy(3)`.
+
+ **splice**
+ :manpage:`splice(2)` is used to transfer the data and
+ :manpage:`vmsplice(2)` to transfer data from user space to the
+ kernel.
+
+ **sg**
+ SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
+ ioctl, or if the target is an sg character device we use
+ :manpage:`read(2)` and :manpage:`write(2)` for asynchronous
+ I/O. Requires :option:`filename` option to specify either block or
+ character devices. This engine supports trim operations.
+ The sg engine includes engine specific options.
+
+ **libzbc**
+ Read, write, trim and ZBC/ZAC operations to a zoned
+ block device using libzbc library. The target can be
+ either an SG character device or a block device file.
+
+ **null**
+ Doesn't transfer any data, just pretends to. This is mainly used to
+ exercise fio itself and for debugging/testing purposes.
+
+ **net**
+ Transfer over the network to given ``host:port``. Depending on the
+ :option:`protocol` used, the :option:`hostname`, :option:`port`,
+ :option:`listen` and :option:`filename` options are used to specify
+ what sort of connection to make, while the :option:`protocol` option
+ determines which protocol will be used. This engine defines engine
+ specific options.
+
+ **netsplice**
+ Like **net**, but uses :manpage:`splice(2)` and
+ :manpage:`vmsplice(2)` to map data and send/receive.
+ This engine defines engine specific options.
+
+ **cpuio**
+ Doesn't transfer any data, but burns CPU cycles according to the
+ :option:`cpuload`, :option:`cpuchunks` and :option:`cpumode` options.
+ Setting :option:`cpuload`\=85 will cause that job to do nothing but burn 85%
+ of the CPU. In case of SMP machines, use :option:`numjobs`\=<nr_of_cpu>
+ to get desired CPU usage, as the cpuload only loads a
+ single CPU at the desired rate. A job never finishes unless there is
+ at least one non-cpuio job.
+ Setting :option:`cpumode`\=qsort replace the default noop instructions loop
+ by a qsort algorithm to consume more energy.
+
+ **rdma**
+ The RDMA I/O engine supports both RDMA memory semantics
+ (RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
+ InfiniBand, RoCE and iWARP protocols. This engine defines engine
+ specific options.
+
+ **falloc**
+ I/O engine that does regular fallocate to simulate data transfer as
+ fio ioengine.
+
+ DDIR_READ
+ does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
+
+ DDIR_WRITE
+ does fallocate(,mode = 0).
+
+ DDIR_TRIM
+ does fallocate(,mode = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
+
+ **ftruncate**
+ I/O engine that sends :manpage:`ftruncate(2)` operations in response
+ to write (DDIR_WRITE) events. Each ftruncate issued sets the file's
+ size to the current block offset. :option:`blocksize` is ignored.
+
+ **e4defrag**
+ I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
+ defragment activity in request to DDIR_WRITE event.
+
+ **rados**
+ I/O engine supporting direct access to Ceph Reliable Autonomic
+ Distributed Object Store (RADOS) via librados. This ioengine
+ defines engine specific options.
+
+ **rbd**
+ I/O engine supporting direct access to Ceph Rados Block Devices
+ (RBD) via librbd without the need to use the kernel rbd driver. This
+ ioengine defines engine specific options.
+
+ **http**
+ I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to
+ a WebDAV or S3 endpoint. This ioengine defines engine specific options.
+
+ This engine only supports direct IO of iodepth=1; you need to scale this
+ via numjobs. blocksize defines the size of the objects to be created.
+
+ TRIM is translated to object deletion.
+
+ **gfapi**
+ Using GlusterFS libgfapi sync interface to direct access to
+ GlusterFS volumes without having to go through FUSE. This ioengine
+ defines engine specific options.
+
+ **gfapi_async**
+ Using GlusterFS libgfapi async interface to direct access to
+ GlusterFS volumes without having to go through FUSE. This ioengine
+ defines engine specific options.
+
+ **libhdfs**
+ Read and write through Hadoop (HDFS). The :option:`filename` option
+ is used to specify host,port of the hdfs name-node to connect. This
+ engine interprets offsets a little differently. In HDFS, files once
+ created cannot be modified so random writes are not possible. To
+ imitate this the libhdfs engine expects a bunch of small files to be
+ created over HDFS and will randomly pick a file from them
+ based on the offset generated by fio backend (see the example
+ job file to create such files, use ``rw=write`` option). Please
+ note, it may be necessary to set environment variables to work
+ with HDFS/libhdfs properly. Each job uses its own connection to
+ HDFS.
+
+ **mtd**
+ Read, write and erase an MTD character device (e.g.,
+ :file:`/dev/mtd0`). Discards are treated as erases. Depending on the
+ underlying device type, the I/O may have to go in a certain pattern,
+ e.g., on NAND, writing sequentially to erase blocks and discarding
+ before overwriting. The `trimwrite` mode works well for this
+ constraint.
+
+ **pmemblk**
+ Read and write using filesystem DAX to a file on a filesystem
+ mounted with DAX on a persistent memory device through the PMDK
+ libpmemblk library.
+
+ **dev-dax**
+ Read and write using device DAX to a persistent memory device (e.g.,
+ /dev/dax0.0) through the PMDK libpmem library.
+
+ **external**
+ Prefix to specify loading an external I/O engine object file. Append
+ the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load
+ ioengine :file:`foo.o` in :file:`/tmp`. The path can be either
+ absolute or relative. See :file:`engines/skeleton_external.c` for
+ details of writing an external I/O engine.
+
+ **filecreate**
+ Simply create the files and do no I/O to them. You still need to
+ set `filesize` so that all the accounting still occurs, but no
+ actual I/O will be done other than creating the file.
+
+ **filestat**
+ Simply do stat() and do no I/O to the file. You need to set 'filesize'
+ and 'nrfiles', so that files will be created.
+ This engine is to measure file lookup and meta data access.
+
+ **filedelete**
+ Simply delete the files by unlink() and do no I/O to them. You need to set 'filesize'
+ and 'nrfiles', so that the files will be created.
+ This engine is to measure file delete.
+
+ **libpmem**
+ Read and write using mmap I/O to a file on a filesystem
+ mounted with DAX on a persistent memory device through the PMDK
+ libpmem library.
+
+ **ime_psync**
+ Synchronous read and write using DDN's Infinite Memory Engine (IME).
+ This engine is very basic and issues calls to IME whenever an IO is
+ queued.
+
+ **ime_psyncv**
+ Synchronous read and write using DDN's Infinite Memory Engine (IME).
+ This engine uses iovecs and will try to stack as much IOs as possible
+ (if the IOs are "contiguous" and the IO depth is not exceeded)
+ before issuing a call to IME.
+
+ **ime_aio**
+ Asynchronous read and write using DDN's Infinite Memory Engine (IME).
+ This engine will try to stack as much IOs as possible by creating
+ requests for IME. FIO will then decide when to commit these requests.
+ **libiscsi**
+ Read and write iscsi lun with libiscsi.
+ **nbd**
+ Read and write a Network Block Device (NBD).
+
+ **libcufile**
+ I/O engine supporting libcufile synchronous access to nvidia-fs and a
+ GPUDirect Storage-supported filesystem. This engine performs
+ I/O without transferring buffers between user-space and the kernel,
+ unless :option:`verify` is set or :option:`cuda_io` is `posix`.
+ :option:`iomem` must not be `cudamalloc`. This ioengine defines
+ engine specific options.
+ **dfs**
+ I/O engine supporting asynchronous read and write operations to the
+ DAOS File System (DFS) via libdfs.
+
+ **nfs**
+ I/O engine supporting asynchronous read and write operations to
+ NFS filesystems from userspace via libnfs. This is useful for
+ achieving higher concurrency and thus throughput than is possible
+ via kernel NFS.
+
+ **exec**
+ Execute 3rd party tools. Could be used to perform monitoring during jobs runtime.
+
+I/O engine specific parameters
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In addition, there are some parameters which are only valid when a specific
+:option:`ioengine` is in use. These are used identically to normal parameters,
+with the caveat that when used on the command line, they must come after the
+:option:`ioengine` that defines them is selected.
+
+.. option:: cmdprio_percentage=int[,int] : [io_uring] [libaio]
+
+ Set the percentage of I/O that will be issued with the highest priority.
+ Default: 0. A single value applies to reads and writes. Comma-separated
+ values may be specified for reads and writes. For this option to be
+ effective, NCQ priority must be supported and enabled, and `direct=1'
+ option must be used. fio must also be run as the root user. Unlike
+ slat/clat/lat stats, which can be tracked and reported independently, per
+ priority stats only track and report a single type of latency. By default,
+ completion latency (clat) will be reported, if :option:`lat_percentiles` is
+ set, total latency (lat) will be reported.
+
+.. option:: cmdprio_class=int[,int] : [io_uring] [libaio]
+
+ Set the I/O priority class to use for I/Os that must be issued with
+ a priority when :option:`cmdprio_percentage` or
+ :option:`cmdprio_bssplit` is set. If not specified when
+ :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
+ this defaults to the highest priority class. A single value applies
+ to reads and writes. Comma-separated values may be specified for
+ reads and writes. See :manpage:`ionice(1)`. See also the
+ :option:`prioclass` option.
+
+.. option:: cmdprio=int[,int] : [io_uring] [libaio]
+
+ Set the I/O priority value to use for I/Os that must be issued with
+ a priority when :option:`cmdprio_percentage` or
+ :option:`cmdprio_bssplit` is set. If not specified when
+ :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
+ this defaults to 0.
+ Linux limits us to a positive value between 0 and 7, with 0 being the
+ highest. A single value applies to reads and writes. Comma-separated
+ values may be specified for reads and writes. See :manpage:`ionice(1)`.
+ Refer to an appropriate manpage for other operating systems since
+ meaning of priority may differ. See also the :option:`prio` option.
+
+.. option:: cmdprio_bssplit=str[,str] : [io_uring] [libaio]
+ To get a finer control over I/O priority, this option allows
+ specifying the percentage of IOs that must have a priority set
+ depending on the block size of the IO. This option is useful only
+ when used together with the :option:`bssplit` option, that is,
+ multiple different block sizes are used for reads and writes.
+
+ The first accepted format for this option is the same as the format of
+ the :option:`bssplit` option:
+
+ cmdprio_bssplit=blocksize/percentage:blocksize/percentage
+
+ In this case, each entry will use the priority class and priority
+ level defined by the options :option:`cmdprio_class` and
+ :option:`cmdprio` respectively.
+
+ The second accepted format for this option is:
+
+ cmdprio_bssplit=blocksize/percentage/class/level:blocksize/percentage/class/level
+
+ In this case, the priority class and priority level is defined inside
+ each entry. In comparison with the first accepted format, the second
+ accepted format does not restrict all entries to have the same priority
+ class and priority level.
+
+ For both formats, only the read and write data directions are supported,
+ values for trim IOs are ignored. This option is mutually exclusive with
+ the :option:`cmdprio_percentage` option.
+
+.. option:: fixedbufs : [io_uring]
+
+ If fio is asked to do direct IO, then Linux will map pages for each
+ IO call, and release them when IO is done. If this option is set, the
+ pages are pre-mapped before IO is started. This eliminates the need to
+ map and release for each IO. This is more efficient, and reduces the
+ IO latency as well.
+
+.. option:: hipri : [io_uring]
+
+ If this option is set, fio will attempt to use polled IO completions.
+ Normal IO completions generate interrupts to signal the completion of
+ IO, polled completions do not. Hence they are require active reaping
+ by the application. The benefits are more efficient IO for high IOPS
+ scenarios, and lower latencies for low queue depth IO.
+
+.. option:: registerfiles : [io_uring]
+
+ With this option, fio registers the set of files being used with the
+ kernel. This avoids the overhead of managing file counts in the kernel,
+ making the submission and completion part more lightweight. Required
+ for the below :option:`sqthread_poll` option.
+
+.. option:: sqthread_poll : [io_uring]
+
+ Normally fio will submit IO by issuing a system call to notify the
+ kernel of available items in the SQ ring. If this option is set, the
+ act of submitting IO will be done by a polling thread in the kernel.
+ This frees up cycles for fio, at the cost of using more CPU in the
+ system.
+
+.. option:: sqthread_poll_cpu : [io_uring]
+
+ When :option:`sqthread_poll` is set, this option provides a way to
+ define which CPU should be used for the polling thread.
+
+.. option:: userspace_reap : [libaio]
+
+ Normally, with the libaio engine in use, fio will use the
+ :manpage:`io_getevents(2)` system call to reap newly returned events. With
+ this flag turned on, the AIO ring will be read directly from user-space to
+ reap events. The reaping mode is only enabled when polling for a minimum of
+ 0 events (e.g. when :option:`iodepth_batch_complete` `=0`).
+
+.. option:: hipri : [pvsync2]
+
+ Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority
+ than normal.
+
+.. option:: hipri_percentage : [pvsync2]
+
+ When hipri is set this determines the probability of a pvsync2 I/O being high
+ priority. The default is 100%.
+
+.. option:: nowait : [pvsync2] [libaio] [io_uring]
+
+ By default if a request cannot be executed immediately (e.g. resource starvation,
+ waiting on locks) it is queued and the initiating process will be blocked until
+ the required resource becomes free.
+
+ This option sets the RWF_NOWAIT flag (supported from the 4.14 Linux kernel) and
+ the call will return instantly with EAGAIN or a partial result rather than waiting.
+
+ It is useful to also use ignore_error=EAGAIN when using this option.
+
+ Note: glibc 2.27, 2.28 have a bug in syscall wrappers preadv2, pwritev2.
+ They return EOPNOTSUP instead of EAGAIN.
+
+ For cached I/O, using this option usually means a request operates only with
+ cached data. Currently the RWF_NOWAIT flag does not supported for cached write.
+
+ For direct I/O, requests will only succeed if cache invalidation isn't required,
+ file blocks are fully allocated and the disk request could be issued immediately.
+
+.. option:: cpuload=int : [cpuio]
+
+ Attempt to use the specified percentage of CPU cycles. This is a mandatory
+ option when using cpuio I/O engine.
+
+.. option:: cpuchunks=int : [cpuio]
+
+ Split the load into cycles of the given time. In microseconds.
+
+.. option:: cpumode=str : [cpuio]
+
+ Specify how to stress the CPU. It can take these two values:
+
+ **noop**
+ This is the default where the CPU executes noop instructions.
+ **qsort**
+ Replace the default noop instructions loop with a qsort algorithm to
+ consume more energy.
+
+.. option:: exit_on_io_done=bool : [cpuio]
+
+ Detect when I/O threads are done, then exit.
+
+.. option:: namenode=str : [libhdfs]
+
+ The hostname or IP address of a HDFS cluster namenode to contact.
+
+.. option:: port=int
+
+ [libhdfs]
+
+ The listening port of the HFDS cluster namenode.
+
+ [netsplice], [net]
+
+ The TCP or UDP port to bind to or connect to. If this is used with
+ :option:`numjobs` to spawn multiple instances of the same job type, then
+ this will be the starting port number since fio will use a range of
+ ports.
+
+ [rdma], [librpma_*]
+
+ The port to use for RDMA-CM communication. This should be the same value
+ on the client and the server side.
+
+.. option:: hostname=str : [netsplice] [net] [rdma]
+
+ The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If the job
+ is a TCP listener or UDP reader, the hostname is not used and must be omitted
+ unless it is a valid UDP multicast address.
+
+.. option:: serverip=str : [librpma_*]
+
+ The IP address to be used for RDMA-CM based I/O.
+
+.. option:: direct_write_to_pmem=bool : [librpma_*]
+
+ Set to 1 only when Direct Write to PMem from the remote host is possible.
+ Otherwise, set to 0.
+
+.. option:: busy_wait_polling=bool : [librpma_*_server]
+
+ Set to 0 to wait for completion instead of busy-wait polling completion.
+ Default: 1.
+
+.. option:: interface=str : [netsplice] [net]
+
+ The IP address of the network interface used to send or receive UDP
+ multicast.
+
+.. option:: ttl=int : [netsplice] [net]
+
+ Time-to-live value for outgoing UDP multicast packets. Default: 1.
+
+.. option:: nodelay=bool : [netsplice] [net]
+
+ Set TCP_NODELAY on TCP connections.
+
+.. option:: protocol=str, proto=str : [netsplice] [net]
+
+ The network protocol to use. Accepted values are:
+
+ **tcp**
+ Transmission control protocol.
+ **tcpv6**
+ Transmission control protocol V6.
+ **udp**
+ User datagram protocol.
+ **udpv6**
+ User datagram protocol V6.
+ **unix**
+ UNIX domain socket.
+
+ When the protocol is TCP or UDP, the port must also be given, as well as the
+ hostname if the job is a TCP listener or UDP reader. For unix sockets, the
+ normal :option:`filename` option should be used and the port is invalid.
+
+.. option:: listen : [netsplice] [net]
+
+ For TCP network connections, tell fio to listen for incoming connections
+ rather than initiating an outgoing connection. The :option:`hostname` must
+ be omitted if this option is used.
+
+.. option:: pingpong : [netsplice] [net]
+
+ Normally a network writer will just continue writing data, and a network
+ reader will just consume packages. If ``pingpong=1`` is set, a writer will
+ send its normal payload to the reader, then wait for the reader to send the
+ same payload back. This allows fio to measure network latencies. The
+ submission and completion latencies then measure local time spent sending or
+ receiving, and the completion latency measures how long it took for the
+ other end to receive and send back. For UDP multicast traffic
+ ``pingpong=1`` should only be set for a single reader when multiple readers
+ are listening to the same address.
+
+.. option:: window_size : [netsplice] [net]
+
+ Set the desired socket buffer size for the connection.
+
+.. option:: mss : [netsplice] [net]
+
+ Set the TCP maximum segment size (TCP_MAXSEG).
+
+.. option:: donorname=str : [e4defrag]
+
+ File will be used as a block donor (swap extents between files).
+
+.. option:: inplace=int : [e4defrag]
+
+ Configure donor file blocks allocation strategy:
+
+ **0**
+ Default. Preallocate donor's file on init.
+ **1**
+ Allocate space immediately inside defragment event, and free right
+ after event.
+
+.. option:: clustername=str : [rbd,rados]
+
+ Specifies the name of the Ceph cluster.
+
+.. option:: rbdname=str : [rbd]
+
+ Specifies the name of the RBD.
+
+.. option:: pool=str : [rbd,rados]
+
+ Specifies the name of the Ceph pool containing RBD or RADOS data.
+
+.. option:: clientname=str : [rbd,rados]
+
+ Specifies the username (without the 'client.' prefix) used to access the
+ Ceph cluster. If the *clustername* is specified, the *clientname* shall be
+ the full *type.id* string. If no type. prefix is given, fio will add
+ 'client.' by default.
+
+.. option:: busy_poll=bool : [rbd,rados]
+
+ Poll store instead of waiting for completion. Usually this provides better
+ throughput at cost of higher(up to 100%) CPU utilization.
+
+.. option:: touch_objects=bool : [rados]
+
+ During initialization, touch (create if do not exist) all objects (files).
+ Touching all objects affects ceph caches and likely impacts test results.
+ Enabled by default.
+
+.. option:: skip_bad=bool : [mtd]
+
+ Skip operations against known bad blocks.
+
+.. option:: hdfsdirectory : [libhdfs]
+
+ libhdfs will create chunk in this HDFS directory.
+
+.. option:: chunk_size : [libhdfs]
+
+ The size of the chunk to use for each file.
+
+.. option:: verb=str : [rdma]
+
+ The RDMA verb to use on this side of the RDMA ioengine connection. Valid
+ values are write, read, send and recv. These correspond to the equivalent
+ RDMA verbs (e.g. write = rdma_write etc.). Note that this only needs to be
+ specified on the client side of the connection. See the examples folder.
+
+.. option:: bindname=str : [rdma]
+
+ The name to use to bind the local RDMA-CM connection to a local RDMA device.
+ This could be a hostname or an IPv4 or IPv6 address. On the server side this
+ will be passed into the rdma_bind_addr() function and on the client site it
+ will be used in the rdma_resolve_add() function. This can be useful when
+ multiple paths exist between the client and the server or in certain loopback
+ configurations.
+
+.. option:: stat_type=str : [filestat]
+
+ Specify stat system call type to measure lookup/getattr performance.
+ Default is **stat** for :manpage:`stat(2)`.
+
+.. option:: readfua=bool : [sg]
+
+ With readfua option set to 1, read operations include
+ the force unit access (fua) flag. Default is 0.
+
+.. option:: writefua=bool : [sg]
+
+ With writefua option set to 1, write operations include
+ the force unit access (fua) flag. Default is 0.
+
+.. option:: sg_write_mode=str : [sg]
+
+ Specify the type of write commands to issue. This option can take three values:
+
+ **write**
+ This is the default where write opcodes are issued as usual.
+ **write_and_verify**
+ Issue WRITE AND VERIFY commands. The BYTCHK bit is set to 0. This
+ directs the device to carry out a medium verification with no data
+ comparison. The writefua option is ignored with this selection.
+ **verify**
+ This option is deprecated. Use write_and_verify instead.
+ **write_same**
+ Issue WRITE SAME commands. This transfers a single block to the device
+ and writes this same block of data to a contiguous sequence of LBAs
+ beginning at the specified offset. fio's block size parameter specifies
+ the amount of data written with each command. However, the amount of data
+ actually transferred to the device is equal to the device's block
+ (sector) size. For a device with 512 byte sectors, blocksize=8k will
+ write 16 sectors with each command. fio will still generate 8k of data
+ for each command but only the first 512 bytes will be used and
+ transferred to the device. The writefua option is ignored with this
+ selection.
+ **same**
+ This option is deprecated. Use write_same instead.
+ **write_same_ndob**
+ Issue WRITE SAME(16) commands as above but with the No Data Output
+ Buffer (NDOB) bit set. No data will be transferred to the device with
+ this bit set. Data written will be a pre-determined pattern such as
+ all zeroes.
+ **write_stream**
+ Issue WRITE STREAM(16) commands. Use the **stream_id** option to specify
+ the stream identifier.
+ **verify_bytchk_00**
+ Issue VERIFY commands with BYTCHK set to 00. This directs the
+ device to carry out a medium verification with no data comparison.
+ **verify_bytchk_01**
+ Issue VERIFY commands with BYTCHK set to 01. This directs the device to
+ compare the data on the device with the data transferred to the device.
+ **verify_bytchk_11**
+ Issue VERIFY commands with BYTCHK set to 11. This transfers a
+ single block to the device and compares the contents of this block with the
+ data on the device beginning at the specified offset. fio's block size
+ parameter specifies the total amount of data compared with this command.
+ However, only one block (sector) worth of data is transferred to the device.
+ This is similar to the WRITE SAME command except that data is compared instead
+ of written.
+
+.. option:: stream_id=int : [sg]
+
+ Set the stream identifier for WRITE STREAM commands. If this is set to 0 (which is not
+ a valid stream identifier) fio will open a stream and then close it when done. Default
+ is 0.
+
+.. option:: hipri : [sg]
+
+ If this option is set, fio will attempt to use polled IO completions.
+ This will have a similar effect as (io_uring)hipri. Only SCSI READ and
+ WRITE commands will have the SGV4_FLAG_HIPRI set (not UNMAP (trim) nor
+ VERIFY). Older versions of the Linux sg driver that do not support
+ hipri will simply ignore this flag and do normal IO. The Linux SCSI
+ Low Level Driver (LLD) that "owns" the device also needs to support
+ hipri (also known as iopoll and mq_poll). The MegaRAID driver is an
+ example of a SCSI LLD. Default: clear (0) which does normal
+ (interrupted based) IO.
+
+.. option:: http_host=str : [http]
+
+ Hostname to connect to. For S3, this could be the bucket hostname.
+ Default is **localhost**
+
+.. option:: http_user=str : [http]
+
+ Username for HTTP authentication.
+
+.. option:: http_pass=str : [http]
+
+ Password for HTTP authentication.
+
+.. option:: https=str : [http]
+
+ Enable HTTPS instead of http. *on* enables HTTPS; *insecure*
+ will enable HTTPS, but disable SSL peer verification (use with
+ caution!). Default is **off**
+
+.. option:: http_mode=str : [http]
+
+ Which HTTP access mode to use: *webdav*, *swift*, or *s3*.
+ Default is **webdav**
+
+.. option:: http_s3_region=str : [http]
+
+ The S3 region/zone string.
+ Default is **us-east-1**
+
+.. option:: http_s3_key=str : [http]
+
+ The S3 secret key.
+
+.. option:: http_s3_keyid=str : [http]
+
+ The S3 key/access id.
+
+.. option:: http_swift_auth_token=str : [http]
+
+ The Swift auth token. See the example configuration file on how
+ to retrieve this.
+
+.. option:: http_verbose=int : [http]
+
+ Enable verbose requests from libcurl. Useful for debugging. 1
+ turns on verbose logging from libcurl, 2 additionally enables
+ HTTP IO tracing. Default is **0**
+
+.. option:: uri=str : [nbd]
+
+ Specify the NBD URI of the server to test. The string
+ is a standard NBD URI
+ (see https://github.com/NetworkBlockDevice/nbd/tree/master/doc).
+ Example URIs: nbd://localhost:10809
+ nbd+unix:///?socket=/tmp/socket
+ nbds://tlshost/exportname
+
+.. option:: gpu_dev_ids=str : [libcufile]
+
+ Specify the GPU IDs to use with CUDA. This is a colon-separated list of
+ int. GPUs are assigned to workers roundrobin. Default is 0.
+
+.. option:: cuda_io=str : [libcufile]
+
+ Specify the type of I/O to use with CUDA. Default is **cufile**.
+
+ **cufile**
+ Use libcufile and nvidia-fs. This option performs I/O directly
+ between a GPUDirect Storage filesystem and GPU buffers,
+ avoiding use of a bounce buffer. If :option:`verify` is set,
+ cudaMemcpy is used to copy verificaton data between RAM and GPU.
+ Verification data is copied from RAM to GPU before a write
+ and from GPU to RAM after a read. :option:`direct` must be 1.
+ **posix**
+ Use POSIX to perform I/O with a RAM buffer, and use cudaMemcpy
+ to transfer data between RAM and the GPUs. Data is copied from
+ GPU to RAM before a write and copied from RAM to GPU after a
+ read. :option:`verify` does not affect use of cudaMemcpy.
+
+.. option:: pool=str : [dfs]
+
+ Specify the label or UUID of the DAOS pool to connect to.
+
+.. option:: cont=str : [dfs]
+
+ Specify the label or UUID of the DAOS container to open.
+
+.. option:: chunk_size=int : [dfs]
+
+ Specificy a different chunk size (in bytes) for the dfs file.
+ Use DAOS container's chunk size by default.
+
+.. option:: object_class=str : [dfs]
+
+ Specificy a different object class for the dfs file.
+ Use DAOS container's object class by default.
+
+.. option:: nfs_url=str : [nfs]
+
+ URL in libnfs format, eg nfs://<server|ipv4|ipv6>/path[?arg=val[&arg=val]*]
+ Refer to the libnfs README for more details.
+
+.. option:: program=str : [exec]
+
+ Specify the program to execute.
+
+.. option:: arguments=str : [exec]
+
+ Specify arguments to pass to program.
+ Some special variables can be expanded to pass fio's job details to the program.
+
+ **%r**
+ Replaced by the duration of the job in seconds.
+ **%n**
+ Replaced by the name of the job.
+
+.. option:: grace_time=int : [exec]
+
+ Specify the time between the SIGTERM and SIGKILL signals. Default is 1 second.
+
+.. option:: std_redirect=bool : [exec]
+
+ If set, stdout and stderr streams are redirected to files named from the job name. Default is true.
+
+I/O depth
+~~~~~~~~~
+
+.. option:: iodepth=int
+
+ Number of I/O units to keep in flight against the file. Note that
+ increasing *iodepth* beyond 1 will not affect synchronous ioengines (except
+ for small degrees when :option:`verify_async` is in use). Even async
+ engines may impose OS restrictions causing the desired depth not to be
+ achieved. This may happen on Linux when using libaio and not setting
+ :option:`direct`\=1, since buffered I/O is not async on that OS. Keep an
+ eye on the I/O depth distribution in the fio output to verify that the
+ achieved depth is as expected. Default: 1.
+
+.. option:: iodepth_batch_submit=int, iodepth_batch=int
+
+ This defines how many pieces of I/O to submit at once. It defaults to 1
+ which means that we submit each I/O as soon as it is available, but can be
+ raised to submit bigger batches of I/O at the time. If it is set to 0 the
+ :option:`iodepth` value will be used.
+
+.. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int
+
+ This defines how many pieces of I/O to retrieve at once. It defaults to 1
+ which means that we'll ask for a minimum of 1 I/O in the retrieval process
+ from the kernel. The I/O retrieval will go on until we hit the limit set by
+ :option:`iodepth_low`. If this variable is set to 0, then fio will always
+ check for completed events before queuing more I/O. This helps reduce I/O
+ latency, at the cost of more retrieval system calls.
+
+.. option:: iodepth_batch_complete_max=int
+
+ This defines maximum pieces of I/O to retrieve at once. This variable should
+ be used along with :option:`iodepth_batch_complete_min`\=int variable,
+ specifying the range of min and max amount of I/O which should be
+ retrieved. By default it is equal to the :option:`iodepth_batch_complete_min`
+ value.
+
+ Example #1::
+
+ iodepth_batch_complete_min=1
+ iodepth_batch_complete_max=<iodepth>
+
+ which means that we will retrieve at least 1 I/O and up to the whole
+ submitted queue depth. If none of I/O has been completed yet, we will wait.
+
+ Example #2::
+
+ iodepth_batch_complete_min=0
+ iodepth_batch_complete_max=<iodepth>
+
+ which means that we can retrieve up to the whole submitted queue depth, but
+ if none of I/O has been completed yet, we will NOT wait and immediately exit
+ the system call. In this example we simply do polling.
+
+.. option:: iodepth_low=int
+
+ The low water mark indicating when to start filling the queue
+ again. Defaults to the same as :option:`iodepth`, meaning that fio will
+ attempt to keep the queue full at all times. If :option:`iodepth` is set to
+ e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of
+ 16 requests, it will let the depth drain down to 4 before starting to fill
+ it again.
+
+.. option:: serialize_overlap=bool
+
+ Serialize in-flight I/Os that might otherwise cause or suffer from data races.
+ When two or more I/Os are submitted simultaneously, there is no guarantee that
+ the I/Os will be processed or completed in the submitted order. Further, if
+ two or more of those I/Os are writes, any overlapping region between them can
+ become indeterminate/undefined on certain storage. These issues can cause
+ verification to fail erratically when at least one of the racing I/Os is
+ changing data and the overlapping region has a non-zero size. Setting
+ ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
+ serializing in-flight I/Os that have a non-zero overlap. Note that setting
+ this option can reduce both performance and the :option:`iodepth` achieved.
+
+ This option only applies to I/Os issued for a single job except when it is
+ enabled along with :option:`io_submit_mode`\=offload. In offload mode, fio
+ will check for overlap among all I/Os submitted by offload jobs with :option:`serialize_overlap`
+ enabled.
+
+ Default: false.
+
+.. option:: io_submit_mode=str
+
+ This option controls how fio submits the I/O to the I/O engine. The default
+ is `inline`, which means that the fio job threads submit and reap I/O
+ directly. If set to `offload`, the job threads will offload I/O submission
+ to a dedicated pool of I/O threads. This requires some coordination and thus
+ has a bit of extra overhead, especially for lower queue depth I/O where it
+ can increase latencies. The benefit is that fio can manage submission rates
+ independently of the device completion rates. This avoids skewed latency
+ reporting if I/O gets backed up on the device side (the coordinated omission
+ problem). Note that this option cannot reliably be used with async IO
+ engines.
+
+
+I/O rate
+~~~~~~~~
+
+.. option:: thinktime=time
+
+ Stall the job for the specified period of time after an I/O has completed before issuing the
+ next. May be used to simulate processing being done by an application.
+ When the unit is omitted, the value is interpreted in microseconds. See
+ :option:`thinktime_blocks`, :option:`thinktime_iotime` and :option:`thinktime_spin`.
+
+.. option:: thinktime_spin=time
+
+ Only valid if :option:`thinktime` is set - pretend to spend CPU time doing
+ something with the data received, before falling back to sleeping for the
+ rest of the period specified by :option:`thinktime`. When the unit is
+ omitted, the value is interpreted in microseconds.
+
+.. option:: thinktime_blocks=int
+
+ Only valid if :option:`thinktime` is set - control how many blocks to issue,
+ before waiting :option:`thinktime` usecs. If not set, defaults to 1 which will make
+ fio wait :option:`thinktime` usecs after every block. This effectively makes any
+ queue depth setting redundant, since no more than 1 I/O will be queued
+ before we have to complete it and do our :option:`thinktime`. In other words, this
+ setting effectively caps the queue depth if the latter is larger.
+
+.. option:: thinktime_blocks_type=str
+
+ Only valid if :option:`thinktime` is set - control how :option:`thinktime_blocks`
+ triggers. The default is `complete`, which triggers thinktime when fio completes
+ :option:`thinktime_blocks` blocks. If this is set to `issue`, then the trigger happens
+ at the issue side.
+
+.. option:: thinktime_iotime=time
+
+ Only valid if :option:`thinktime` is set - control :option:`thinktime`
+ interval by time. The :option:`thinktime` stall is repeated after IOs
+ are executed for :option:`thinktime_iotime`. For example,
+ ``--thinktime_iotime=9s --thinktime=1s`` repeat 10-second cycle with IOs
+ for 9 seconds and stall for 1 second. When the unit is omitted,
+ :option:`thinktime_iotime` is interpreted as a number of seconds. If
+ this option is used together with :option:`thinktime_blocks`, the
+ :option:`thinktime` stall is repeated after :option:`thinktime_iotime`
+ or after :option:`thinktime_blocks` IOs, whichever happens first.
+
+.. option:: rate=int[,int][,int]
+
+ Cap the bandwidth used by this job. The number is in bytes/sec, the normal
+ suffix rules apply. Comma-separated values may be specified for reads,
+ writes, and trims as described in :option:`blocksize`.
+
+ For example, using `rate=1m,500k` would limit reads to 1MiB/sec and writes to
+ 500KiB/sec. Capping only reads or writes can be done with `rate=,500k` or
+ `rate=500k,` where the former will only limit writes (to 500KiB/sec) and the
+ latter will only limit reads.
+
+.. option:: rate_min=int[,int][,int]
+
+ Tell fio to do whatever it can to maintain at least this bandwidth. Failing
+ to meet this requirement will cause the job to exit. Comma-separated values
+ may be specified for reads, writes, and trims as described in
+ :option:`blocksize`.
+
+.. option:: rate_iops=int[,int][,int]
+
+ Cap the bandwidth to this number of IOPS. Basically the same as
+ :option:`rate`, just specified independently of bandwidth. If the job is
+ given a block size range instead of a fixed value, the smallest block size
+ is used as the metric. Comma-separated values may be specified for reads,
+ writes, and trims as described in :option:`blocksize`.
+
+.. option:: rate_iops_min=int[,int][,int]
+
+ If fio doesn't meet this rate of I/O, it will cause the job to exit.
+ Comma-separated values may be specified for reads, writes, and trims as
+ described in :option:`blocksize`.
+
+.. option:: rate_process=str
+
+ This option controls how fio manages rated I/O submissions. The default is
+ `linear`, which submits I/O in a linear fashion with fixed delays between
+ I/Os that gets adjusted based on I/O completion rates. If this is set to
+ `poisson`, fio will submit I/O based on a more real world random request
+ flow, known as the Poisson process
+ (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be
+ 10^6 / IOPS for the given workload.
+
+.. option:: rate_ignore_thinktime=bool
+
+ By default, fio will attempt to catch up to the specified rate setting,
+ if any kind of thinktime setting was used. If this option is set, then
+ fio will ignore the thinktime and continue doing IO at the specified
+ rate, instead of entering a catch-up mode after thinktime is done.
+
+
+I/O latency
+~~~~~~~~~~~
+
+.. option:: latency_target=time
+
+ If set, fio will attempt to find the max performance point that the given
+ workload will run at while maintaining a latency below this target. When
+ the unit is omitted, the value is interpreted in microseconds. See
+ :option:`latency_window` and :option:`latency_percentile`.
+
+.. option:: latency_window=time
+
+ Used with :option:`latency_target` to specify the sample window that the job
+ is run at varying queue depths to test the performance. When the unit is
+ omitted, the value is interpreted in microseconds.
+
+.. option:: latency_percentile=float
+
+ The percentage of I/Os that must fall within the criteria specified by
+ :option:`latency_target` and :option:`latency_window`. If not set, this
+ defaults to 100.0, meaning that all I/Os must be equal or below to the value
+ set by :option:`latency_target`.
+
+.. option:: latency_run=bool
+
+ Used with :option:`latency_target`. If false (default), fio will find
+ the highest queue depth that meets :option:`latency_target` and exit. If
+ true, fio will continue running and try to meet :option:`latency_target`
+ by adjusting queue depth.
+
+.. option:: max_latency=time[,time][,time]
+
+ If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
+ maximum latency. When the unit is omitted, the value is interpreted in
+ microseconds. Comma-separated values may be specified for reads, writes,
+ and trims as described in :option:`blocksize`.
+
+.. option:: rate_cycle=int
+
+ Average bandwidth for :option:`rate` and :option:`rate_min` over this number
+ of milliseconds. Defaults to 1000.
+
+
+I/O replay
+~~~~~~~~~~
+
+.. option:: write_iolog=str
+
+ Write the issued I/O patterns to the specified file. See
+ :option:`read_iolog`. Specify a separate file for each job, otherwise the
+ iologs will be interspersed and the file may be corrupt.
+
+.. option:: read_iolog=str
+
+ Open an iolog with the specified filename and replay the I/O patterns it
+ contains. This can be used to store a workload and replay it sometime
+ later. The iolog given may also be a blktrace binary file, which allows fio
+ to replay a workload captured by :command:`blktrace`. See
+ :manpage:`blktrace(8)` for how to capture such logging data. For blktrace
+ replay, the file needs to be turned into a blkparse binary data file first
+ (``blkparse <device> -o /dev/null -d file_for_fio.bin``).
+ You can specify a number of files by separating the names with a ':'
+ character. See the :option:`filename` option for information on how to
+ escape ':' characters within the file names. These files will
+ be sequentially assigned to job clones created by :option:`numjobs`.
+ '-' is a reserved name, meaning read from stdin, notably if
+ :option:`filename` is set to '-' which means stdin as well, then
+ this flag can't be set to '-'.
+
+.. option:: read_iolog_chunked=bool
+
+ Determines how iolog is read. If false(default) entire :option:`read_iolog`
+ will be read at once. If selected true, input from iolog will be read
+ gradually. Useful when iolog is very large, or it is generated.
+
+.. option:: merge_blktrace_file=str
+
+ When specified, rather than replaying the logs passed to :option:`read_iolog`,
+ the logs go through a merge phase which aggregates them into a single
+ blktrace. The resulting file is then passed on as the :option:`read_iolog`
+ parameter. The intention here is to make the order of events consistent.
+ This limits the influence of the scheduler compared to replaying multiple
+ blktraces via concurrent jobs.
+
+.. option:: merge_blktrace_scalars=float_list
+
+ This is a percentage based option that is index paired with the list of
+ files passed to :option:`read_iolog`. When merging is performed, scale
+ the time of each event by the corresponding amount. For example,
+ ``--merge_blktrace_scalars="50:100"`` runs the first trace in halftime
+ and the second trace in realtime. This knob is separately tunable from
+ :option:`replay_time_scale` which scales the trace during runtime and
+ does not change the output of the merge unlike this option.
+
+.. option:: merge_blktrace_iters=float_list
+
+ This is a whole number option that is index paired with the list of files
+ passed to :option:`read_iolog`. When merging is performed, run each trace
+ for the specified number of iterations. For example,
+ ``--merge_blktrace_iters="2:1"`` runs the first trace for two iterations
+ and the second trace for one iteration.
+
+.. option:: replay_no_stall=bool
+
+ When replaying I/O with :option:`read_iolog` the default behavior is to
+ attempt to respect the timestamps within the log and replay them with the
+ appropriate delay between IOPS. By setting this variable fio will not
+ respect the timestamps and attempt to replay them as fast as possible while
+ still respecting ordering. The result is the same I/O pattern to a given
+ device, but different timings.
+
+.. option:: replay_time_scale=int
+
+ When replaying I/O with :option:`read_iolog`, fio will honor the
+ original timing in the trace. With this option, it's possible to scale
+ the time. It's a percentage option, if set to 50 it means run at 50%
+ the original IO rate in the trace. If set to 200, run at twice the
+ original IO rate. Defaults to 100.
+
+.. option:: replay_redirect=str
+
+ While replaying I/O patterns using :option:`read_iolog` the default behavior
+ is to replay the IOPS onto the major/minor device that each IOP was recorded
+ from. This is sometimes undesirable because on a different machine those
+ major/minor numbers can map to a different device. Changing hardware on the
+ same system can also result in a different major/minor mapping.
+ ``replay_redirect`` causes all I/Os to be replayed onto the single specified
+ device regardless of the device it was recorded
+ from. i.e. :option:`replay_redirect`\= :file:`/dev/sdc` would cause all I/O
+ in the blktrace or iolog to be replayed onto :file:`/dev/sdc`. This means
+ multiple devices will be replayed onto a single device, if the trace
+ contains multiple devices. If you want multiple devices to be replayed
+ concurrently to multiple redirected devices you must blkparse your trace
+ into separate traces and replay them with independent fio invocations.
+ Unfortunately this also breaks the strict time ordering between multiple
+ device accesses.
+
+.. option:: replay_align=int
+
+ Force alignment of the byte offsets in a trace to this value. The value
+ must be a power of 2.
+
+.. option:: replay_scale=int
+
+ Scale byte offsets down by this factor when replaying traces. Should most
+ likely use :option:`replay_align` as well.
+
+.. option:: replay_skip=str
+
+ Sometimes it's useful to skip certain IO types in a replay trace.
+ This could be, for instance, eliminating the writes in the trace.
+ Or not replaying the trims/discards, if you are redirecting to
+ a device that doesn't support them. This option takes a comma
+ separated list of read, write, trim, sync.
+
+
+Threads, processes and job synchronization
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. option:: thread
+
+ Fio defaults to creating jobs by using fork, however if this option is
+ given, fio will create jobs by using POSIX Threads' function
+ :manpage:`pthread_create(3)` to create threads instead.
+
+.. option:: wait_for=str
+
+ If set, the current job won't be started until all workers of the specified
+ waitee job are done.
+
+ ``wait_for`` operates on the job name basis, so there are a few
+ limitations. First, the waitee must be defined prior to the waiter job
+ (meaning no forward references). Second, if a job is being referenced as a
+ waitee, it must have a unique name (no duplicate waitees).
+
+.. option:: nice=int
+
+ Run the job with the given nice value. See man :manpage:`nice(2)`.
+
+ On Windows, values less than -15 set the process class to "High"; -1 through
+ -15 set "Above Normal"; 1 through 15 "Below Normal"; and above 15 "Idle"
+ priority class.
+
+.. option:: prio=int
+
+ Set the I/O priority value of this job. Linux limits us to a positive value
+ between 0 and 7, with 0 being the highest. See man
+ :manpage:`ionice(1)`. Refer to an appropriate manpage for other operating
+ systems since meaning of priority may differ. For per-command priority
+ setting, see I/O engine specific :option:`cmdprio_percentage` and
+ :option:`cmdprio` options.
+
+.. option:: prioclass=int
+
+ Set the I/O priority class. See man :manpage:`ionice(1)`. For per-command
+ priority setting, see I/O engine specific :option:`cmdprio_percentage`
+ and :option:`cmdprio_class` options.
+
+.. option:: cpus_allowed=str
+
+ Controls the same options as :option:`cpumask`, but accepts a textual
+ specification of the permitted CPUs instead and CPUs are indexed from 0. So
+ to use CPUs 0 and 5 you would specify ``cpus_allowed=0,5``. This option also
+ allows a range of CPUs to be specified -- say you wanted a binding to CPUs
+ 0, 5, and 8 to 15, you would set ``cpus_allowed=0,5,8-15``.
+
+ On Windows, when ``cpus_allowed`` is unset only CPUs from fio's current
+ processor group will be used and affinity settings are inherited from the
+ system. An fio build configured to target Windows 7 makes options that set
+ CPUs processor group aware and values will set both the processor group
+ and a CPU from within that group. For example, on a system where processor
+ group 0 has 40 CPUs and processor group 1 has 32 CPUs, ``cpus_allowed``
+ values between 0 and 39 will bind CPUs from processor group 0 and
+ ``cpus_allowed`` values between 40 and 71 will bind CPUs from processor
+ group 1. When using ``cpus_allowed_policy=shared`` all CPUs specified by a
+ single ``cpus_allowed`` option must be from the same processor group. For
+ Windows fio builds not built for Windows 7, CPUs will only be selected from
+ (and be relative to) whatever processor group fio happens to be running in
+ and CPUs from other processor groups cannot be used.
+
+.. option:: cpus_allowed_policy=str
+
+ Set the policy of how fio distributes the CPUs specified by
+ :option:`cpus_allowed` or :option:`cpumask`. Two policies are supported:
+
+ **shared**
+ All jobs will share the CPU set specified.
+ **split**
+ Each job will get a unique CPU from the CPU set.
+
+ **shared** is the default behavior, if the option isn't specified. If
+ **split** is specified, then fio will assign one cpu per job. If not
+ enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
+ in the set.
+
+.. option:: cpumask=int
+
+ Set the CPU affinity of this job. The parameter given is a bit mask of
+ allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
+ and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
+ :manpage:`sched_setaffinity(2)`. This may not work on all supported
+ operating systems or kernel versions. This option doesn't work well for a
+ higher CPU count than what you can store in an integer mask, so it can only
+ control cpus 1-32. For boxes with larger CPU counts, use
+ :option:`cpus_allowed`.
+
+.. option:: numa_cpu_nodes=str
+
+ Set this job running on specified NUMA nodes' CPUs. The arguments allow
+ comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable
+ NUMA options support, fio must be built on a system with libnuma-dev(el)
+ installed.
+
+.. option:: numa_mem_policy=str
+
+ Set this job's memory policy and corresponding NUMA nodes. Format of the
+ arguments::
+
+ <mode>[:<nodelist>]
+
+ ``mode`` is one of the following memory policies: ``default``, ``prefer``,
+ ``bind``, ``interleave`` or ``local``. For ``default`` and ``local`` memory
+ policies, no node needs to be specified. For ``prefer``, only one node is
+ allowed. For ``bind`` and ``interleave`` the ``nodelist`` may be as
+ follows: a comma delimited list of numbers, A-B ranges, or `all`.
+
+.. option:: cgroup=str
+
+ Add job to this control group. If it doesn't exist, it will be created. The
+ system must have a mounted cgroup blkio mount point for this to work. If
+ your system doesn't have it mounted, you can do so with::
+
+ # mount -t cgroup -o blkio none /cgroup
+
+.. option:: cgroup_weight=int
+
+ Set the weight of the cgroup to this value. See the documentation that comes
+ with the kernel, allowed values are in the range of 100..1000.
+
+.. option:: cgroup_nodelete=bool
+
+ Normally fio will delete the cgroups it has created after the job
+ completion. To override this behavior and to leave cgroups around after the
+ job completion, set ``cgroup_nodelete=1``. This can be useful if one wants
+ to inspect various cgroup files after job completion. Default: false.
+
+.. option:: flow_id=int
+
+ The ID of the flow. If not specified, it defaults to being a global
+ flow. See :option:`flow`.
+
+.. option:: flow=int
+
+ Weight in token-based flow control. If this value is used, then there is a
+ 'flow counter' which is used to regulate the proportion of activity between
+ two or more jobs. Fio attempts to keep this flow counter near zero. The
+ ``flow`` parameter stands for how much should be added or subtracted to the
+ flow counter on each iteration of the main I/O loop. That is, if one job has
+ ``flow=8`` and another job has ``flow=-1``, then there will be a roughly 1:8
+ ratio in how much one runs vs the other.
+
+.. option:: flow_sleep=int
+
+ The period of time, in microseconds, to wait after the flow counter
+ has exceeded its proportion before retrying operations.
+
+.. option:: stonewall, wait_for_previous
+
+ Wait for preceding jobs in the job file to exit, before starting this
+ one. Can be used to insert serialization points in the job file. A stone
+ wall also implies starting a new reporting group, see
+ :option:`group_reporting`.
+
+.. option:: exitall
+
+ By default, fio will continue running all other jobs when one job finishes.
+ Sometimes this is not the desired action. Setting ``exitall`` will instead
+ make fio terminate all jobs in the same group, as soon as one job of that
+ group finishes.
+
+.. option:: exit_what
+
+ By default, fio will continue running all other jobs when one job finishes.
+ Sometimes this is not the desired action. Setting ``exit_all`` will
+ instead make fio terminate all jobs in the same group. The option
+ ``exit_what`` allows to control which jobs get terminated when ``exitall`` is
+ enabled. The default is ``group`` and does not change the behaviour of
+ ``exitall``. The setting ``all`` terminates all jobs. The setting ``stonewall``
+ terminates all currently running jobs across all groups and continues execution
+ with the next stonewalled group.
+
+.. option:: exec_prerun=str
+
+ Before running this job, issue the command specified through
+ :manpage:`system(3)`. Output is redirected in a file called
+ :file:`jobname.prerun.txt`.
+
+.. option:: exec_postrun=str
+
+ After the job completes, issue the command specified though
+ :manpage:`system(3)`. Output is redirected in a file called
+ :file:`jobname.postrun.txt`.
+
+.. option:: uid=int
+
+ Instead of running as the invoking user, set the user ID to this value
+ before the thread/process does any work.
+
+.. option:: gid=int
+
+ Set group ID, see :option:`uid`.
+
+
+Verification
+~~~~~~~~~~~~
+
+.. option:: verify_only
+
+ Do not perform specified workload, only verify data still matches previous
+ invocation of this workload. This option allows one to check data multiple
+ times at a later date without overwriting it. This option makes sense only
+ for workloads that write data, and does not support workloads with the
+ :option:`time_based` option set.
+
+.. option:: do_verify=bool
+
+ Run the verify phase after a write phase. Only valid if :option:`verify` is
+ set. Default: true.
+
+.. option:: verify=str
+
+ If writing to a file, fio can verify the file contents after each iteration
+ of the job. Each verification method also implies verification of special
+ header, which is written to the beginning of each block. This header also
+ includes meta information, like offset of the block, block number, timestamp
+ when block was written, etc. :option:`verify` can be combined with
+ :option:`verify_pattern` option. The allowed values are:
+
+ **md5**
+ Use an md5 sum of the data area and store it in the header of
+ each block.
+
+ **crc64**
+ Use an experimental crc64 sum of the data area and store it in the
+ header of each block.
+
+ **crc32c**
+ Use a crc32c sum of the data area and store it in the header of
+ each block. This will automatically use hardware acceleration
+ (e.g. SSE4.2 on an x86 or CRC crypto extensions on ARM64) but will
+ fall back to software crc32c if none is found. Generally the
+ fastest checksum fio supports when hardware accelerated.
+
+ **crc32c-intel**
+ Synonym for crc32c.
+
+ **crc32**
+ Use a crc32 sum of the data area and store it in the header of each
+ block.
+
+ **crc16**
+ Use a crc16 sum of the data area and store it in the header of each
+ block.
+
+ **crc7**
+ Use a crc7 sum of the data area and store it in the header of each
+ block.
+
+ **xxhash**
+ Use xxhash as the checksum function. Generally the fastest software
+ checksum that fio supports.
+
+ **sha512**
+ Use sha512 as the checksum function.
+
+ **sha256**
+ Use sha256 as the checksum function.
+
+ **sha1**
+ Use optimized sha1 as the checksum function.
+
+ **sha3-224**
+ Use optimized sha3-224 as the checksum function.
+
+ **sha3-256**
+ Use optimized sha3-256 as the checksum function.
+
+ **sha3-384**
+ Use optimized sha3-384 as the checksum function.
+
+ **sha3-512**
+ Use optimized sha3-512 as the checksum function.
+
+ **meta**
+ This option is deprecated, since now meta information is included in
+ generic verification header and meta verification happens by
+ default. For detailed information see the description of the
+ :option:`verify` setting. This option is kept because of
+ compatibility's sake with old configurations. Do not use it.
+
+ **pattern**
+ Verify a strict pattern. Normally fio includes a header with some
+ basic information and checksumming, but if this option is set, only
+ the specific pattern set with :option:`verify_pattern` is verified.
+
+ **null**
+ Only pretend to verify. Useful for testing internals with
+ :option:`ioengine`\=null, not for much else.
+
+ This option can be used for repeated burn-in tests of a system to make sure
+ that the written data is also correctly read back. If the data direction
+ given is a read or random read, fio will assume that it should verify a
+ previously written file. If the data direction includes any form of write,
+ the verify will be of the newly written data.
+
+ To avoid false verification errors, do not use the norandommap option when
+ verifying data with async I/O engines and I/O depths > 1. Or use the
+ norandommap and the lfsr random generator together to avoid writing to the
+ same offset with muliple outstanding I/Os.
+
+.. option:: verify_offset=int
+
+ Swap the verification header with data somewhere else in the block before
+ writing. It is swapped back before verifying.
+
+.. option:: verify_interval=int
+
+ Write the verification header at a finer granularity than the
+ :option:`blocksize`. It will be written for chunks the size of
+ ``verify_interval``. :option:`blocksize` should divide this evenly.
+
+.. option:: verify_pattern=str
+
+ If set, fio will fill the I/O buffers with this pattern. Fio defaults to
+ filling with totally random bytes, but sometimes it's interesting to fill
+ with a known pattern for I/O verification purposes. Depending on the width
+ of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it can
+ be either a decimal or a hex number). The ``verify_pattern`` if larger than
+ a 32-bit quantity has to be a hex number that starts with either "0x" or
+ "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o
+ format, which means that for each block offset will be written and then
+ verified back, e.g.::
+
+ verify_pattern=%o
+
+ Or use combination of everything::
+
+ verify_pattern=0xff%o"abcd"-12
+
+.. option:: verify_fatal=bool
+
+ Normally fio will keep checking the entire contents before quitting on a
+ block verification failure. If this option is set, fio will exit the job on
+ the first observed failure. Default: false.
+
+.. option:: verify_dump=bool
+
+ If set, dump the contents of both the original data block and the data block
+ we read off disk to files. This allows later analysis to inspect just what
+ kind of data corruption occurred. Off by default.
+
+.. option:: verify_async=int
+
+ Fio will normally verify I/O inline from the submitting thread. This option
+ takes an integer describing how many async offload threads to create for I/O
+ verification instead, causing fio to offload the duty of verifying I/O
+ contents to one or more separate threads. If using this offload option, even
+ sync I/O engines can benefit from using an :option:`iodepth` setting higher
+ than 1, as it allows them to have I/O in flight while verifies are running.
+ Defaults to 0 async threads, i.e. verification is not asynchronous.
+
+.. option:: verify_async_cpus=str
+
+ Tell fio to set the given CPU affinity on the async I/O verification
+ threads. See :option:`cpus_allowed` for the format used.
+
+.. option:: verify_backlog=int
+
+ Fio will normally verify the written contents of a job that utilizes verify
+ once that job has completed. In other words, everything is written then
+ everything is read back and verified. You may want to verify continually
+ instead for a variety of reasons. Fio stores the meta data associated with
+ an I/O block in memory, so for large verify workloads, quite a bit of memory
+ would be used up holding this meta data. If this option is enabled, fio will
+ write only N blocks before verifying these blocks.
+
+.. option:: verify_backlog_batch=int
+
+ Control how many blocks fio will verify if :option:`verify_backlog` is
+ set. If not set, will default to the value of :option:`verify_backlog`
+ (meaning the entire queue is read back and verified). If
+ ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all
+ blocks will be verified, if ``verify_backlog_batch`` is larger than
+ :option:`verify_backlog`, some blocks will be verified more than once.
+
+.. option:: verify_state_save=bool
+
+ When a job exits during the write phase of a verify workload, save its
+ current state. This allows fio to replay up until that point, if the verify
+ state is loaded for the verify read phase. The format of the filename is,
+ roughly::
+
+ <type>-<jobname>-<jobindex>-verify.state.
+
+ <type> is "local" for a local run, "sock" for a client/server socket
+ connection, and "ip" (192.168.0.1, for instance) for a networked
+ client/server connection. Defaults to true.
+
+.. option:: verify_state_load=bool
+
+ If a verify termination trigger was used, fio stores the current write state
+ of each thread. This can be used at verification time so that fio knows how
+ far it should verify. Without this information, fio will run a full
+ verification pass, according to the settings in the job file used. Default
+ false.
+
+.. option:: trim_percentage=int
+
+ Number of verify blocks to discard/trim.
+
+.. option:: trim_verify_zero=bool
+
+ Verify that trim/discarded blocks are returned as zeros.
+
+.. option:: trim_backlog=int
+
+ Trim after this number of blocks are written.
+
+.. option:: trim_backlog_batch=int
+
+ Trim this number of I/O blocks.
+
+.. option:: experimental_verify=bool
+
+ Enable experimental verification.
+
+Steady state
+~~~~~~~~~~~~
+
+.. option:: steadystate=str:float, ss=str:float
+
+ Define the criterion and limit for assessing steady state performance. The
+ first parameter designates the criterion whereas the second parameter sets
+ the threshold. When the criterion falls below the threshold for the
+ specified duration, the job will stop. For example, `iops_slope:0.1%` will
+ direct fio to terminate the job when the least squares regression slope
+ falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled
+ this will apply to all jobs in the group. Below is the list of available
+ steady state assessment criteria. All assessments are carried out using only
+ data from the rolling collection window. Threshold limits can be expressed
+ as a fixed value or as a percentage of the mean in the collection window.
+
+ When using this feature, most jobs should include the :option:`time_based`
+ and :option:`runtime` options or the :option:`loops` option so that fio does not
+ stop running after it has covered the full size of the specified file(s) or device(s).
+
+ **iops**
+ Collect IOPS data. Stop the job if all individual IOPS measurements
+ are within the specified limit of the mean IOPS (e.g., ``iops:2``
+ means that all individual IOPS values must be within 2 of the mean,
+ whereas ``iops:0.2%`` means that all individual IOPS values must be
+ within 0.2% of the mean IOPS to terminate the job).
+
+ **iops_slope**
+ Collect IOPS data and calculate the least squares regression
+ slope. Stop the job if the slope falls below the specified limit.
+
+ **bw**
+ Collect bandwidth data. Stop the job if all individual bandwidth
+ measurements are within the specified limit of the mean bandwidth.
+
+ **bw_slope**
+ Collect bandwidth data and calculate the least squares regression
+ slope. Stop the job if the slope falls below the specified limit.
+
+.. option:: steadystate_duration=time, ss_dur=time
+
+ A rolling window of this duration will be used to judge whether steady state
+ has been reached. Data will be collected once per second. The default is 0
+ which disables steady state detection. When the unit is omitted, the
+ value is interpreted in seconds.
+
+.. option:: steadystate_ramp_time=time, ss_ramp=time
+
+ Allow the job to run for the specified duration before beginning data
+ collection for checking the steady state job termination criterion. The
+ default is 0. When the unit is omitted, the value is interpreted in seconds.
+
+
+Measurements and reporting
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. option:: per_job_logs=bool
+
+ If set, this generates bw/clat/iops log with per file private filenames. If
+ not set, jobs with identical names will share the log filename. Default:
+ true.
+
+.. option:: group_reporting
+
+ It may sometimes be interesting to display statistics for groups of jobs as
+ a whole instead of for each individual job. This is especially true if
+ :option:`numjobs` is used; looking at individual thread/process output
+ quickly becomes unwieldy. To see the final report per-group instead of
+ per-job, use :option:`group_reporting`. Jobs in a file will be part of the
+ same reporting group, unless if separated by a :option:`stonewall`, or by
+ using :option:`new_group`.
+
+.. option:: new_group
+
+ Start a new reporting group. See: :option:`group_reporting`. If not given,
+ all jobs in a file will be part of the same reporting group, unless
+ separated by a :option:`stonewall`.
+
+.. option:: stats=bool
+
+ By default, fio collects and shows final output results for all jobs
+ that run. If this option is set to 0, then fio will ignore it in
+ the final stat output.
+
+.. option:: write_bw_log=str
+
+ If given, write a bandwidth log for this job. Can be used to store data of
+ the bandwidth of the jobs in their lifetime.
+
+ If no str argument is given, the default filename of
+ :file:`jobname_type.x.log` is used. Even when the argument is given, fio
+ will still append the type of log. So if one specifies::
+
+ write_bw_log=foo
+
+ The actual log name will be :file:`foo_bw.x.log` where `x` is the index
+ of the job (`1..N`, where `N` is the number of jobs). If
+ :option:`per_job_logs` is false, then the filename will not include the
+ `.x` job index.
+
+ The included :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
+ text files into nice graphs. See `Log File Formats`_ for how data is
+ structured within the file.
+
+.. option:: write_lat_log=str
+
+ Same as :option:`write_bw_log`, except this option creates I/O
+ submission (e.g., :file:`name_slat.x.log`), completion (e.g.,
+ :file:`name_clat.x.log`), and total (e.g., :file:`name_lat.x.log`)
+ latency files instead. See :option:`write_bw_log` for details about
+ the filename format and `Log File Formats`_ for how data is structured
+ within the files.
+
+.. option:: write_hist_log=str
+
+ Same as :option:`write_bw_log` but writes an I/O completion latency
+ histogram file (e.g., :file:`name_hist.x.log`) instead. Note that this
+ file will be empty unless :option:`log_hist_msec` has also been set.
+ See :option:`write_bw_log` for details about the filename format and
+ `Log File Formats`_ for how data is structured within the file.
+
+.. option:: write_iops_log=str
+
+ Same as :option:`write_bw_log`, but writes an IOPS file (e.g.
+ :file:`name_iops.x.log`) instead. Because fio defaults to individual
+ I/O logging, the value entry in the IOPS log will be 1 unless windowed
+ logging (see :option:`log_avg_msec`) has been enabled. See
+ :option:`write_bw_log` for details about the filename format and `Log
+ File Formats`_ for how data is structured within the file.
+
+.. option:: log_entries=int
+
+ By default, fio will log an entry in the iops, latency, or bw log for
+ every I/O that completes. The initial number of I/O log entries is 1024.
+ When the log entries are all used, new log entries are dynamically
+ allocated. This dynamic log entry allocation may negatively impact
+ time-related statistics such as I/O tail latencies (e.g. 99.9th percentile
+ completion latency). This option allows specifying a larger initial
+ number of log entries to avoid run-time allocations of new log entries,
+ resulting in more precise time-related I/O statistics.
+ Also see :option:`log_avg_msec`. Defaults to 1024.
+
+.. option:: log_avg_msec=int
+
+ By default, fio will log an entry in the iops, latency, or bw log for every
+ I/O that completes. When writing to the disk log, that can quickly grow to a
+ very large size. Setting this option makes fio average the each log entry
+ over the specified period of time, reducing the resolution of the log. See
+ :option:`log_max_value` as well. Defaults to 0, logging all entries.
+ Also see `Log File Formats`_.
+
+.. option:: log_hist_msec=int
+
+ Same as :option:`log_avg_msec`, but logs entries for completion latency
+ histograms. Computing latency percentiles from averages of intervals using
+ :option:`log_avg_msec` is inaccurate. Setting this option makes fio log
+ histogram entries over the specified period of time, reducing log sizes for
+ high IOPS devices while retaining percentile accuracy. See
+ :option:`log_hist_coarseness` and :option:`write_hist_log` as well.
+ Defaults to 0, meaning histogram logging is disabled.
+
+.. option:: log_hist_coarseness=int
+
+ Integer ranging from 0 to 6, defining the coarseness of the resolution of
+ the histogram logs enabled with :option:`log_hist_msec`. For each increment
+ in coarseness, fio outputs half as many bins. Defaults to 0, for which
+ histogram logs contain 1216 latency bins. See :option:`write_hist_log`
+ and `Log File Formats`_.
+
+.. option:: log_max_value=bool
+
+ If :option:`log_avg_msec` is set, fio logs the average over that window. If
+ you instead want to log the maximum value, set this option to 1. Defaults to
+ 0, meaning that averaged values are logged.
+
+.. option:: log_offset=bool
+
+ If this is set, the iolog options will include the byte offset for the I/O
+ entry as well as the other data values. Defaults to 0 meaning that
+ offsets are not present in logs. Also see `Log File Formats`_.
+
+.. option:: log_compression=int
+
+ If this is set, fio will compress the I/O logs as it goes, to keep the
+ memory footprint lower. When a log reaches the specified size, that chunk is
+ removed and compressed in the background. Given that I/O logs are fairly
+ highly compressible, this yields a nice memory savings for longer runs. The
+ downside is that the compression will consume some background CPU cycles, so
+ it may impact the run. This, however, is also true if the logging ends up
+ consuming most of the system memory. So pick your poison. The I/O logs are
+ saved normally at the end of a run, by decompressing the chunks and storing
+ them in the specified log file. This feature depends on the availability of
+ zlib.
+
+.. option:: log_compression_cpus=str
+
+ Define the set of CPUs that are allowed to handle online log compression for
+ the I/O jobs. This can provide better isolation between performance
+ sensitive jobs, and background compression work. See
+ :option:`cpus_allowed` for the format used.
+
+.. option:: log_store_compressed=bool
+
+ If set, fio will store the log files in a compressed format. They can be
+ decompressed with fio, using the :option:`--inflate-log` command line
+ parameter. The files will be stored with a :file:`.fz` suffix.
+
+.. option:: log_unix_epoch=bool
+
+ If set, fio will log Unix timestamps to the log files produced by enabling
+ write_type_log for each log type, instead of the default zero-based
+ timestamps.
+
+.. option:: log_alternate_epoch=bool
+
+ If set, fio will log timestamps based on the epoch used by the clock specified
+ in the log_alternate_epoch_clock_id option, to the log files produced by
+ enabling write_type_log for each log type, instead of the default zero-based
+ timestamps.
+
+.. option:: log_alternate_epoch_clock_id=int
+
+ Specifies the clock_id to be used by clock_gettime to obtain the alternate epoch
+ if either log_unix_epoch or log_alternate_epoch are true. Otherwise has no
+ effect. Default value is 0, or CLOCK_REALTIME.
+
+.. option:: block_error_percentiles=bool
+
+ If set, record errors in trim block-sized units from writes and trims and
+ output a histogram of how many trims it took to get to errors, and what kind
+ of error was encountered.
+
+.. option:: bwavgtime=int
+
+ Average the calculated bandwidth over the given time. Value is specified in
+ milliseconds. If the job also does bandwidth logging through
+ :option:`write_bw_log`, then the minimum of this option and
+ :option:`log_avg_msec` will be used. Default: 500ms.
+
+.. option:: iopsavgtime=int
+
+ Average the calculated IOPS over the given time. Value is specified in
+ milliseconds. If the job also does IOPS logging through
+ :option:`write_iops_log`, then the minimum of this option and
+ :option:`log_avg_msec` will be used. Default: 500ms.
+
+.. option:: disk_util=bool
+
+ Generate disk utilization statistics, if the platform supports it.
+ Default: true.
+
+.. option:: disable_lat=bool
+
+ Disable measurements of total latency numbers. Useful only for cutting back
+ the number of calls to :manpage:`gettimeofday(2)`, as that does impact
+ performance at really high IOPS rates. Note that to really get rid of a
+ large amount of these calls, this option must be used with
+ :option:`disable_slat` and :option:`disable_bw_measurement` as well.
+
+.. option:: disable_clat=bool
+
+ Disable measurements of completion latency numbers. See
+ :option:`disable_lat`.
+
+.. option:: disable_slat=bool
+
+ Disable measurements of submission latency numbers. See
+ :option:`disable_lat`.
+
+.. option:: disable_bw_measurement=bool, disable_bw=bool
+
+ Disable measurements of throughput/bandwidth numbers. See
+ :option:`disable_lat`.
+
+.. option:: slat_percentiles=bool
+
+ Report submission latency percentiles. Submission latency is not recorded
+ for synchronous ioengines.
+
+.. option:: clat_percentiles=bool
+
+ Report completion latency percentiles.
+
+.. option:: lat_percentiles=bool
+
+ Report total latency percentiles. Total latency is the sum of submission
+ latency and completion latency.
+
+.. option:: percentile_list=float_list
+
+ Overwrite the default list of percentiles for latencies and the block error
+ histogram. Each number is a floating point number in the range (0,100], and
+ the maximum length of the list is 20. Use ``:`` to separate the numbers. For
+ example, ``--percentile_list=99.5:99.9`` will cause fio to report the
+ latency durations below which 99.5% and 99.9% of the observed latencies fell,
+ respectively.
+
+.. option:: significant_figures=int
+
+ If using :option:`--output-format` of `normal`, set the significant
+ figures to this value. Higher values will yield more precise IOPS and
+ throughput units, while lower values will round. Requires a minimum
+ value of 1 and a maximum value of 10. Defaults to 4.
+
+
+Error handling
+~~~~~~~~~~~~~~
+
+.. option:: exitall_on_error
+
+ When one job finishes in error, terminate the rest. The default is to wait
+ for each job to finish.
+
+.. option:: continue_on_error=str
+
+ Normally fio will exit the job on the first observed failure. If this option
+ is set, fio will continue the job when there is a 'non-fatal error' (EIO or
+ EILSEQ) until the runtime is exceeded or the I/O size specified is
+ completed. If this option is used, there are two more stats that are
+ appended, the total error count and the first error. The error field given
+ in the stats is the first error that was hit during the run.
+
+ The allowed values are:
+
+ **none**
+ Exit on any I/O or verify errors.
+
+ **read**
+ Continue on read errors, exit on all others.
+
+ **write**
+ Continue on write errors, exit on all others.
+
+ **io**
+ Continue on any I/O error, exit on all others.
+
+ **verify**
+ Continue on verify errors, exit on all others.
+
+ **all**
+ Continue on all errors.
+
+ **0**
+ Backward-compatible alias for 'none'.
+
+ **1**
+ Backward-compatible alias for 'all'.
+
+.. option:: ignore_error=str
+
+ Sometimes you want to ignore some errors during test in that case you can
+ specify error list for each error type, instead of only being able to
+ ignore the default 'non-fatal error' using :option:`continue_on_error`.
+ ``ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST`` errors for
+ given error type is separated with ':'. Error may be symbol ('ENOSPC',
+ 'ENOMEM') or integer. Example::
+
+ ignore_error=EAGAIN,ENOSPC:122
+
+ This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from
+ WRITE. This option works by overriding :option:`continue_on_error` with
+ the list of errors for each error type if any.
+
+.. option:: error_dump=bool
+
+ If set dump every error even if it is non fatal, true by default. If
+ disabled only fatal error will be dumped.
+
+Running predefined workloads
+----------------------------
+
+Fio includes predefined profiles that mimic the I/O workloads generated by
+other tools.
+
+.. option:: profile=str
+
+ The predefined workload to run. Current profiles are:
+
+ **tiobench**
+ Threaded I/O bench (tiotest/tiobench) like workload.
+
+ **act**
+ Aerospike Certification Tool (ACT) like workload.
+
+To view a profile's additional options use :option:`--cmdhelp` after specifying
+the profile. For example::
+
+ $ fio --profile=act --cmdhelp
+
+Act profile options
+~~~~~~~~~~~~~~~~~~~
+
+.. option:: device-names=str
+ :noindex:
+
+ Devices to use.
+
+.. option:: load=int
+ :noindex:
+
+ ACT load multiplier. Default: 1.
+
+.. option:: test-duration=time
+ :noindex:
+
+ How long the entire test takes to run. When the unit is omitted, the value
+ is given in seconds. Default: 24h.
+
+.. option:: threads-per-queue=int
+ :noindex:
+
+ Number of read I/O threads per device. Default: 8.
+
+.. option:: read-req-num-512-blocks=int
+ :noindex:
+
+ Number of 512B blocks to read at the time. Default: 3.
+
+.. option:: large-block-op-kbytes=int
+ :noindex:
+
+ Size of large block ops in KiB (writes). Default: 131072.
+
+.. option:: prep
+ :noindex:
+
+ Set to run ACT prep phase.
+
+Tiobench profile options
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. option:: size=str
+ :noindex:
+
+ Size in MiB.
+
+.. option:: block=int
+ :noindex:
+
+ Block size in bytes. Default: 4096.
+
+.. option:: numruns=int
+ :noindex:
+
+ Number of runs.
+
+.. option:: dir=str
+ :noindex:
+
+ Test directory.
+
+.. option:: threads=int
+ :noindex:
+
+ Number of threads.
+
+Interpreting the output
+-----------------------
+
+..
+ Example output was based on the following:
+ TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --time_based \
+ --rate=1256k --bs=14K --name=quick --runtime=1s --name=mixed \
+ --runtime=2m --rw=rw
+
+Fio spits out a lot of output. While running, fio will display the status of the
+jobs created. An example of that would be::
+
+ Jobs: 1 (f=1): [_(1),M(1)][24.8%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 01m:31s]
+
+The characters inside the first set of square brackets denote the current status of
+each thread. The first character is the first job defined in the job file, and so
+forth. The possible values (in typical life cycle order) are:
+
++------+-----+-----------------------------------------------------------+
+| Idle | Run | |
++======+=====+===========================================================+
+| P | | Thread setup, but not started. |
++------+-----+-----------------------------------------------------------+
+| C | | Thread created. |
++------+-----+-----------------------------------------------------------+
+| I | | Thread initialized, waiting or generating necessary data. |
++------+-----+-----------------------------------------------------------+
+| | p | Thread running pre-reading file(s). |
++------+-----+-----------------------------------------------------------+
+| | / | Thread is in ramp period. |
++------+-----+-----------------------------------------------------------+
+| | R | Running, doing sequential reads. |
++------+-----+-----------------------------------------------------------+
+| | r | Running, doing random reads. |
++------+-----+-----------------------------------------------------------+
+| | W | Running, doing sequential writes. |
++------+-----+-----------------------------------------------------------+
+| | w | Running, doing random writes. |
++------+-----+-----------------------------------------------------------+
+| | M | Running, doing mixed sequential reads/writes. |
++------+-----+-----------------------------------------------------------+
+| | m | Running, doing mixed random reads/writes. |
++------+-----+-----------------------------------------------------------+
+| | D | Running, doing sequential trims. |
++------+-----+-----------------------------------------------------------+
+| | d | Running, doing random trims. |
++------+-----+-----------------------------------------------------------+
+| | F | Running, currently waiting for :manpage:`fsync(2)`. |
++------+-----+-----------------------------------------------------------+
+| | V | Running, doing verification of written data. |
++------+-----+-----------------------------------------------------------+
+| f | | Thread finishing. |
++------+-----+-----------------------------------------------------------+
+| E | | Thread exited, not reaped by main thread yet. |
++------+-----+-----------------------------------------------------------+
+| _ | | Thread reaped. |
++------+-----+-----------------------------------------------------------+
+| X | | Thread reaped, exited with an error. |
++------+-----+-----------------------------------------------------------+
+| K | | Thread reaped, exited due to signal. |
++------+-----+-----------------------------------------------------------+
+
+..
+ Example output was based on the following:
+ TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --runtime=58m \
+ --time_based --rate=2512k --bs=256K --numjobs=10 \
+ --name=readers --rw=read --name=writers --rw=write
+
+Fio will condense the thread string as not to take up more space on the command
+line than needed. For instance, if you have 10 readers and 10 writers running,
+the output would look like this::
+
+ Jobs: 20 (f=20): [R(10),W(10)][4.0%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 57m:36s]
+
+Note that the status string is displayed in order, so it's possible to tell which of
+the jobs are currently doing what. In the example above this means that jobs 1--10
+are readers and 11--20 are writers.
+
+The other values are fairly self explanatory -- number of threads currently
+running and doing I/O, the number of currently open files (f=), the estimated
+completion percentage, the rate of I/O since last check (read speed listed first,
+then write speed and optionally trim speed) in terms of bandwidth and IOPS,
+and time to completion for the current running group. It's impossible to estimate
+runtime of the following groups (if any).
+
+..
+ Example output was based on the following:
+ TZ=UTC fio --iodepth=16 --ioengine=posixaio --filename=/tmp/fiofile \
+ --direct=1 --size=100M --time_based --runtime=50s --rate_iops=89 \
+ --bs=7K --name=Client1 --rw=write
+
+When fio is done (or interrupted by :kbd:`Ctrl-C`), it will show the data for
+each thread, group of threads, and disks in that order. For each overall thread (or
+group) the output looks like::
+
+ Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
+ write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
+ slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
+ clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
+ lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
+ clat percentiles (usec):
+ | 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
+ | 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
+ | 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
+ | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
+ | 99.99th=[78119]
+ bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
+ iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
+ lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
+ lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
+ lat (msec) : 100=0.65%
+ cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
+ IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
+ submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
+ complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
+ issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
+ latency : target=0, window=0, percentile=100.00%, depth=8
+
+The job name (or first job's name when using :option:`group_reporting`) is printed,
+along with the group id, count of jobs being aggregated, last error id seen (which
+is 0 when there are no errors), pid/tid of that thread and the time the job/group
+completed. Below are the I/O statistics for each data direction performed (showing
+writes in the example above). In the order listed, they denote:
+
+**read/write/trim**
+ The string before the colon shows the I/O direction the statistics
+ are for. **IOPS** is the average I/Os performed per second. **BW**
+ is the average bandwidth rate shown as: value in power of 2 format
+ (value in power of 10 format). The last two values show: (**total
+ I/O performed** in power of 2 format / **runtime** of that thread).
+
+**slat**
+ Submission latency (**min** being the minimum, **max** being the
+ maximum, **avg** being the average, **stdev** being the standard
+ deviation). This is the time it took to submit the I/O. For
+ sync I/O this row is not displayed as the slat is really the
+ completion latency (since queue/complete is one operation there).
+ This value can be in nanoseconds, microseconds or milliseconds ---
+ fio will choose the most appropriate base and print that (in the
+ example above nanoseconds was the best scale). Note: in :option:`--minimal` mode
+ latencies are always expressed in microseconds.
+
+**clat**
+ Completion latency. Same names as slat, this denotes the time from
+ submission to completion of the I/O pieces. For sync I/O, clat will
+ usually be equal (or very close) to 0, as the time from submit to
+ complete is basically just CPU time (I/O has already been done, see slat
+ explanation).
+
+**lat**
+ Total latency. Same names as slat and clat, this denotes the time from
+ when fio created the I/O unit to completion of the I/O operation.
+
+**bw**
+ Bandwidth statistics based on samples. Same names as the xlat stats,
+ but also includes the number of samples taken (**samples**) and an
+ approximate percentage of total aggregate bandwidth this thread
+ received in its group (**per**). This last value is only really
+ useful if the threads in this group are on the same disk, since they
+ are then competing for disk access.
+
+**iops**
+ IOPS statistics based on samples. Same names as bw.
+
+**lat (nsec/usec/msec)**
+ The distribution of I/O completion latencies. This is the time from when
+ I/O leaves fio and when it gets completed. Unlike the separate
+ read/write/trim sections above, the data here and in the remaining
+ sections apply to all I/Os for the reporting group. 250=0.04% means that
+ 0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11%
+ of the I/Os required 250 to 499us for completion.
+
+**cpu**
+ CPU usage. User and system time, along with the number of context
+ switches this thread went through, usage of system and user time, and
+ finally the number of major and minor page faults. The CPU utilization
+ numbers are averages for the jobs in that reporting group, while the
+ context and fault counters are summed.
+
+**IO depths**
+ The distribution of I/O depths over the job lifetime. The numbers are
+ divided into powers of 2 and each entry covers depths from that value
+ up to those that are lower than the next entry -- e.g., 16= covers
+ depths from 16 to 31. Note that the range covered by a depth
+ distribution entry can be different to the range covered by the
+ equivalent submit/complete distribution entry.
+
+**IO submit**
+ How many pieces of I/O were submitting in a single submit call. Each
+ entry denotes that amount and below, until the previous entry -- e.g.,
+ 16=100% means that we submitted anywhere between 9 to 16 I/Os per submit
+ call. Note that the range covered by a submit distribution entry can
+ be different to the range covered by the equivalent depth distribution
+ entry.
+
+**IO complete**
+ Like the above submit number, but for completions instead.
+
+**IO issued rwt**
+ The number of read/write/trim requests issued, and how many of them were
+ short or dropped.
+
+**IO latency**
+ These values are for :option:`latency_target` and related options. When
+ these options are engaged, this section describes the I/O depth required
+ to meet the specified latency target.
+
+..
+ Example output was based on the following:
+ TZ=UTC fio --ioengine=null --iodepth=2 --size=100M --numjobs=2 \
+ --rate_process=poisson --io_limit=32M --name=read --bs=128k \
+ --rate=11M --name=write --rw=write --bs=2k --rate=700k
+
+After each client has been listed, the group statistics are printed. They
+will look like this::
+
+ Run status group 0 (all jobs):
+ READ: bw=20.9MiB/s (21.9MB/s), 10.4MiB/s-10.8MiB/s (10.9MB/s-11.3MB/s), io=64.0MiB (67.1MB), run=2973-3069msec
+ WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
+
+For each data direction it prints:
+
+**bw**
+ Aggregate bandwidth of threads in this group followed by the
+ minimum and maximum bandwidth of all the threads in this group.
+ Values outside of brackets are power-of-2 format and those
+ within are the equivalent value in a power-of-10 format.
+**io**
+ Aggregate I/O performed of all threads in this group. The
+ format is the same as bw.
+**run**
+ The smallest and longest runtimes of the threads in this group.
+
+And finally, the disk statistics are printed. This is Linux specific. They will look like this::
+
+ Disk stats (read/write):
+ sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
+
+Each value is printed for both reads and writes, with reads first. The
+numbers denote:
+
+**ios**
+ Number of I/Os performed by all groups.
+**merge**
+ Number of merges performed by the I/O scheduler.
+**ticks**
+ Number of ticks we kept the disk busy.
+**in_queue**
+ Total time spent in the disk queue.
+**util**
+ The disk utilization. A value of 100% means we kept the disk
+ busy constantly, 50% would be a disk idling half of the time.
+
+It is also possible to get fio to dump the current output while it is running,
+without terminating the job. To do that, send fio the **USR1** signal. You can
+also get regularly timed dumps by using the :option:`--status-interval`
+parameter, or by creating a file in :file:`/tmp` named
+:file:`fio-dump-status`. If fio sees this file, it will unlink it and dump the
+current output status.
+
+
+Terse output
+------------
+
+For scripted usage where you typically want to generate tables or graphs of the
+results, fio can output the results in a semicolon separated format. The format
+is one long line of values, such as::
+
+ 2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
+ A description of this job goes here.
+
+The job description (if provided) follows on a second line for terse v2.
+It appears on the same line for other terse versions.
+
+To enable terse output, use the :option:`--minimal` or
+:option:`--output-format`\=terse command line options. The
+first value is the version of the terse output format. If the output has to be
+changed for some reason, this number will be incremented by 1 to signify that
+change.
+
+Split up, the format is as follows (comments in brackets denote when a
+field was introduced or whether it's specific to some terse version):
+
+ ::
+
+ terse version, fio version [v3], jobname, groupid, error
+
+ READ status::
+
+ Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
+ Submission latency: min, max, mean, stdev (usec)
+ Completion latency: min, max, mean, stdev (usec)
+ Completion latency percentiles: 20 fields (see below)
+ Total latency: min, max, mean, stdev (usec)
+ Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
+ IOPS [v5]: min, max, mean, stdev, number of samples
+
+ WRITE status:
+
+ ::
+
+ Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
+ Submission latency: min, max, mean, stdev (usec)
+ Completion latency: min, max, mean, stdev (usec)
+ Completion latency percentiles: 20 fields (see below)
+ Total latency: min, max, mean, stdev (usec)
+ Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
+ IOPS [v5]: min, max, mean, stdev, number of samples
+
+ TRIM status [all but version 3]:
+
+ Fields are similar to READ/WRITE status.
+
+ CPU usage::
+
+ user, system, context switches, major faults, minor faults
+
+ I/O depths::
+
+ <=1, 2, 4, 8, 16, 32, >=64
+
+ I/O latencies microseconds::
+
+ <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
+
+ I/O latencies milliseconds::
+
+ <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
+
+ Disk utilization [v3]::
+
+ disk name, read ios, write ios, read merges, write merges, read ticks, write ticks,
+ time spent in queue, disk utilization percentage
+
+ Additional Info (dependent on continue_on_error, default off)::
+
+ total # errors, first error code
+
+ Additional Info (dependent on description being set)::
+
+ Text description
+
+Completion latency percentiles can be a grouping of up to 20 sets, so for the
+terse output fio writes all of them. Each field will look like this::
+
+ 1.00%=6112
+
+which is the Xth percentile, and the `usec` latency associated with it.
+
+For `Disk utilization`, all disks used by fio are shown. So for each disk there
+will be a disk utilization section.
+
+Below is a single line containing short names for each of the fields in the
+minimal output v3, separated by semicolons::
+
+ terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth_kb;read_iops;read_runtime_ms;read_slat_min_us;read_slat_max_us;read_slat_mean_us;read_slat_dev_us;read_clat_min_us;read_clat_max_us;read_clat_mean_us;read_clat_dev_us;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min_us;read_lat_max_us;read_lat_mean_us;read_lat_dev_us;read_bw_min_kb;read_bw_max_kb;read_bw_agg_pct;read_bw_mean_kb;read_bw_dev_kb;write_kb;write_bandwidth_kb;write_iops;write_runtime_ms;write_slat_min_us;write_slat_max_us;write_slat_mean_us;write_slat_dev_us;write_clat_min_us;write_clat_max_us;write_clat_mean_us;write_clat_dev_us;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min_us;write_lat_max_us;write_lat_mean_us;write_lat_dev_us;write_bw_min_kb;write_bw_max_kb;write_bw_agg_pct;write_bw_mean_kb;write_bw_dev_kb;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
+
+In client/server mode terse output differs from what appears when jobs are run
+locally. Disk utilization data is omitted from the standard terse output and
+for v3 and later appears on its own separate line at the end of each terse
+reporting cycle.
+
+
+JSON output
+------------
+
+The `json` output format is intended to be both human readable and convenient
+for automated parsing. For the most part its sections mirror those of the
+`normal` output. The `runtime` value is reported in msec and the `bw` value is
+reported in 1024 bytes per second units.
+
+
+JSON+ output
+------------
+
+The `json+` output format is identical to the `json` output format except that it
+adds a full dump of the completion latency bins. Each `bins` object contains a
+set of (key, value) pairs where keys are latency durations and values count how
+many I/Os had completion latencies of the corresponding duration. For example,
+consider:
+
+ "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... }
+
+This data indicates that one I/O required 87,552ns to complete, two I/Os required
+100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
+
+Also included with fio is a Python script `fio_jsonplus_clat2csv` that takes
+json+ output and generates CSV-formatted latency data suitable for plotting.
+
+The latency durations actually represent the midpoints of latency intervals.
+For details refer to :file:`stat.h`.
+
+
+Trace file format
+-----------------
+
+There are two trace file format that you can encounter. The older (v1) format is
+unsupported since version 1.20-rc3 (March 2008). It will still be described
+below in case that you get an old trace and want to understand it.
+
+In any case the trace is a simple text file with a single action per line.
+
+
+Trace file format v1
+~~~~~~~~~~~~~~~~~~~~
+
+Each line represents a single I/O action in the following format::
+
+ rw, offset, length
+
+where `rw=0/1` for read/write, and the `offset` and `length` entries being in bytes.
+
+This format is not supported in fio versions >= 1.20-rc3.
+
+
+Trace file format v2
+~~~~~~~~~~~~~~~~~~~~
+
+The second version of the trace file format was added in fio version 1.17. It
+allows to access more then one file per trace and has a bigger set of possible
+file actions.
+
+The first line of the trace file has to be::
+
+ fio version 2 iolog
+
+Following this can be lines in two different formats, which are described below.
+
+The file management format::
+
+ filename action
+
+The `filename` is given as an absolute path. The `action` can be one of these:
+
+**add**
+ Add the given `filename` to the trace.
+**open**
+ Open the file with the given `filename`. The `filename` has to have
+ been added with the **add** action before.
+**close**
+ Close the file with the given `filename`. The file has to have been
+ opened before.
+
+
+The file I/O action format::
+
+ filename action offset length
+
+The `filename` is given as an absolute path, and has to have been added and
+opened before it can be used with this format. The `offset` and `length` are
+given in bytes. The `action` can be one of these:
+
+**wait**
+ Wait for `offset` microseconds. Everything below 100 is discarded.
+ The time is relative to the previous `wait` statement.
+**read**
+ Read `length` bytes beginning from `offset`.
+**write**
+ Write `length` bytes beginning from `offset`.
+**sync**
+ :manpage:`fsync(2)` the file.
+**datasync**
+ :manpage:`fdatasync(2)` the file.
+**trim**
+ Trim the given file from the given `offset` for `length` bytes.
+
+
+I/O Replay - Merging Traces
+---------------------------
+
+Colocation is a common practice used to get the most out of a machine.
+Knowing which workloads play nicely with each other and which ones don't is
+a much harder task. While fio can replay workloads concurrently via multiple
+jobs, it leaves some variability up to the scheduler making results harder to
+reproduce. Merging is a way to make the order of events consistent.
+
+Merging is integrated into I/O replay and done when a
+:option:`merge_blktrace_file` is specified. The list of files passed to
+:option:`read_iolog` go through the merge process and output a single file
+stored to the specified file. The output file is passed on as if it were the
+only file passed to :option:`read_iolog`. An example would look like::
+
+ $ fio --read_iolog="<file1>:<file2>" --merge_blktrace_file="<output_file>"
+
+Creating only the merged file can be done by passing the command line argument
+:option:`--merge-blktrace-only`.
+
+Scaling traces can be done to see the relative impact of any particular trace
+being slowed down or sped up. :option:`merge_blktrace_scalars` takes in a colon
+separated list of percentage scalars. It is index paired with the files passed
+to :option:`read_iolog`.
+
+With scaling, it may be desirable to match the running time of all traces.
+This can be done with :option:`merge_blktrace_iters`. It is index paired with
+:option:`read_iolog` just like :option:`merge_blktrace_scalars`.
+
+In an example, given two traces, A and B, each 60s long. If we want to see
+the impact of trace A issuing IOs twice as fast and repeat trace A over the
+runtime of trace B, the following can be done::
+
+ $ fio --read_iolog="<trace_a>:"<trace_b>" --merge_blktrace_file"<output_file>" --merge_blktrace_scalars="50:100" --merge_blktrace_iters="2:1"
+
+This runs trace A at 2x the speed twice for approximately the same runtime as
+a single run of trace B.
+
+
+CPU idleness profiling
+----------------------
+
+In some cases, we want to understand CPU overhead in a test. For example, we
+test patches for the specific goodness of whether they reduce CPU usage.
+Fio implements a balloon approach to create a thread per CPU that runs at idle
+priority, meaning that it only runs when nobody else needs the cpu.
+By measuring the amount of work completed by the thread, idleness of each CPU
+can be derived accordingly.
+
+An unit work is defined as touching a full page of unsigned characters. Mean and
+standard deviation of time to complete an unit work is reported in "unit work"
+section. Options can be chosen to report detailed percpu idleness or overall
+system idleness by aggregating percpu stats.
+
+
+Verification and triggers
+-------------------------
+
+Fio is usually run in one of two ways, when data verification is done. The first
+is a normal write job of some sort with verify enabled. When the write phase has
+completed, fio switches to reads and verifies everything it wrote. The second
+model is running just the write phase, and then later on running the same job
+(but with reads instead of writes) to repeat the same I/O patterns and verify
+the contents. Both of these methods depend on the write phase being completed,
+as fio otherwise has no idea how much data was written.
+
+With verification triggers, fio supports dumping the current write state to
+local files. Then a subsequent read verify workload can load this state and know
+exactly where to stop. This is useful for testing cases where power is cut to a
+server in a managed fashion, for instance.
+
+A verification trigger consists of two things:
+
+1) Storing the write state of each job.
+2) Executing a trigger command.
+
+The write state is relatively small, on the order of hundreds of bytes to single
+kilobytes. It contains information on the number of completions done, the last X
+completions, etc.
+
+A trigger is invoked either through creation ('touch') of a specified file in
+the system, or through a timeout setting. If fio is run with
+:option:`--trigger-file`\= :file:`/tmp/trigger-file`, then it will continually
+check for the existence of :file:`/tmp/trigger-file`. When it sees this file, it
+will fire off the trigger (thus saving state, and executing the trigger
+command).
+
+For client/server runs, there's both a local and remote trigger. If fio is
+running as a server backend, it will send the job states back to the client for
+safe storage, then execute the remote trigger, if specified. If a local trigger
+is specified, the server will still send back the write state, but the client
+will then execute the trigger.
+
+Verification trigger example
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Let's say we want to run a powercut test on the remote Linux machine 'server'.
+Our write workload is in :file:`write-test.fio`. We want to cut power to 'server' at
+some point during the run, and we'll run this test from the safety or our local
+machine, 'localbox'. On the server, we'll start the fio backend normally::
+
+ server# fio --server
+
+and on the client, we'll fire off the workload::
+
+ localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
+
+We set :file:`/tmp/my-trigger` as the trigger file, and we tell fio to execute::
+
+ echo b > /proc/sysrq-trigger
+
+on the server once it has received the trigger and sent us the write state. This
+will work, but it's not **really** cutting power to the server, it's merely
+abruptly rebooting it. If we have a remote way of cutting power to the server
+through IPMI or similar, we could do that through a local trigger command
+instead. Let's assume we have a script that does IPMI reboot of a given hostname,
+ipmi-reboot. On localbox, we could then have run fio with a local trigger
+instead::
+
+ localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
+
+For this case, fio would wait for the server to send us the write state, then
+execute ``ipmi-reboot server`` when that happened.
+
+Loading verify state
+~~~~~~~~~~~~~~~~~~~~
+
+To load stored write state, a read verification job file must contain the
+:option:`verify_state_load` option. If that is set, fio will load the previously
+stored state. For a local fio run this is done by loading the files directly,
+and on a client/server run, the server backend will ask the client to send the
+files over and load them from there.
+
+
+Log File Formats
+----------------
+
+Fio supports a variety of log file formats, for logging latencies, bandwidth,
+and IOPS. The logs share a common format, which looks like this:
+
+ *time* (`msec`), *value*, *data direction*, *block size* (`bytes`),
+ *offset* (`bytes`), *command priority*
+
+*Time* for the log entry is always in milliseconds. The *value* logged depends
+on the type of log, it will be one of the following:
+
+ **Latency log**
+ Value is latency in nsecs
+ **Bandwidth log**
+ Value is in KiB/sec
+ **IOPS log**
+ Value is IOPS
+
+*Data direction* is one of the following:
+
+ **0**
+ I/O is a READ
+ **1**
+ I/O is a WRITE
+ **2**
+ I/O is a TRIM
+
+The entry's *block size* is always in bytes. The *offset* is the position in bytes
+from the start of the file for that particular I/O. The logging of the offset can be
+toggled with :option:`log_offset`.
+
+*Command priority* is 0 for normal priority and 1 for high priority. This is controlled
+by the ioengine specific :option:`cmdprio_percentage`.
+
+Fio defaults to logging every individual I/O but when windowed logging is set
+through :option:`log_avg_msec`, either the average (by default) or the maximum
+(:option:`log_max_value` is set) *value* seen over the specified period of time
+is recorded. Each *data direction* seen within the window period will aggregate
+its values in a separate row. Further, when using windowed logging the *block
+size* and *offset* entries will always contain 0.
+
+
+Client/Server
+-------------
+
+Normally fio is invoked as a stand-alone application on the machine where the
+I/O workload should be generated. However, the backend and frontend of fio can
+be run separately i.e., the fio server can generate an I/O workload on the "Device
+Under Test" while being controlled by a client on another machine.
+
+Start the server on the machine which has access to the storage DUT::
+
+ $ fio --server=args
+
+where `args` defines what fio listens to. The arguments are of the form
+``type,hostname`` or ``IP,port``. *type* is either ``ip`` (or ip4) for TCP/IP
+v4, ``ip6`` for TCP/IP v6, or ``sock`` for a local unix domain socket.
+*hostname* is either a hostname or IP address, and *port* is the port to listen
+to (only valid for TCP/IP, not a local socket). Some examples:
+
+1) ``fio --server``
+
+ Start a fio server, listening on all interfaces on the default port (8765).
+
+2) ``fio --server=ip:hostname,4444``
+
+ Start a fio server, listening on IP belonging to hostname and on port 4444.
+
+3) ``fio --server=ip6:::1,4444``
+
+ Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
+
+4) ``fio --server=,4444``
+
+ Start a fio server, listening on all interfaces on port 4444.
+
+5) ``fio --server=1.2.3.4``
+
+ Start a fio server, listening on IP 1.2.3.4 on the default port.
+
+6) ``fio --server=sock:/tmp/fio.sock``
+
+ Start a fio server, listening on the local socket :file:`/tmp/fio.sock`.
+
+Once a server is running, a "client" can connect to the fio server with::
+
+ fio <local-args> --client=<server> <remote-args> <job file(s)>
+
+where `local-args` are arguments for the client where it is running, `server`
+is the connect string, and `remote-args` and `job file(s)` are sent to the
+server. The `server` string follows the same format as it does on the server
+side, to allow IP/hostname/socket and port strings.
+
+Fio can connect to multiple servers this way::
+
+ fio --client=<server1> <job file(s)> --client=<server2> <job file(s)>
+
+If the job file is located on the fio server, then you can tell the server to
+load a local file as well. This is done by using :option:`--remote-config` ::
+
+ fio --client=server --remote-config /path/to/file.fio
+
+Then fio will open this local (to the server) job file instead of being passed
+one from the client.
+
+If you have many servers (example: 100 VMs/containers), you can input a pathname
+of a file containing host IPs/names as the parameter value for the
+:option:`--client` option. For example, here is an example :file:`host.list`
+file containing 2 hostnames::
+
+ host1.your.dns.domain
+ host2.your.dns.domain
+
+The fio command would then be::
+
+ fio --client=host.list <job file(s)>
+
+In this mode, you cannot input server-specific parameters or job files -- all
+servers receive the same job file.
+
+In order to let ``fio --client`` runs use a shared filesystem from multiple
+hosts, ``fio --client`` now prepends the IP address of the server to the
+filename. For example, if fio is using the directory :file:`/mnt/nfs/fio` and is
+writing filename :file:`fileio.tmp`, with a :option:`--client` `hostfile`
+containing two hostnames ``h1`` and ``h2`` with IP addresses 192.168.10.120 and
+192.168.10.121, then fio will create two files::
+
+ /mnt/nfs/fio/192.168.10.120.fileio.tmp
+ /mnt/nfs/fio/192.168.10.121.fileio.tmp
+
+Terse output in client/server mode will differ slightly from what is produced
+when fio is run in stand-alone mode. See the terse output section for details.
.. include:: ../README.rst
-.. include:: ../HOWTO
+.. include:: ../HOWTO.rst
.. include:: ../README.rst
-.. include:: ../HOWTO
+.. include:: ../HOWTO.rst
projects / fio.git / commitdiff