X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=e0403b0803f04cb04ef7a14832dd39b3803c34d8;hp=3c8fbd83adde00d9fc65ae4d4365d11189f39e8e;hb=HEAD;hpb=d19c04d12b6996c4b9f6f4e27dd5a7570eea1ddc diff --git a/HOWTO b/HOWTO deleted file mode 100644 index 3c8fbd83..00000000 --- a/HOWTO +++ /dev/null @@ -1,4296 +0,0 @@ -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 - - 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 `. - 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 `. - -**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: - - **$jobname** - The name of the worker thread or process. - **$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` 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. - **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. - -.. 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:: 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:: 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 ``:`` 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 ** 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=`` - 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=bool - - Fio normally reports statistics on a per data direction basis, meaning that - reads, writes, and trims are accounted and reported separately. If this - option is set fio sums the results and report them as "mixed" instead. - -.. 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 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%. - -.. 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. - -.. 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, FreeBSD, 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[,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. - - 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:: 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=bool - - Use synchronous I/O for buffered writes. For the majority of I/O engines, - this means using O_SYNC. Default: false. - -.. 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. - 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 and limited to :option:`size` in - total (if that is given). If not given, each created file is the same size. - This option overrides :option:`size` in terms of file size, which means - this value is used as a fixed size or possible range of each file. - -.. 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) 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. - - **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` and :option:`cpuchunks` 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`\= - 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. - - **guasi** - The GUASI I/O engine is the Generic Userspace Asynchronous Syscall - Interface approach to async I/O. See - - http://www.xmailserver.org/guasi-lib.html - - for more info on GUASI. - - **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. - - **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). - -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 : [io_uring] [libaio] - - Set the percentage of I/O that will be issued with higher priority by setting - the priority bit. Non-read I/O is likely unaffected by ``cmdprio_percentage``. - This option cannot be used with the `prio` or `prioclass` options. For this - option to set the priority bit properly, NCQ priority must be supported and - enabled and :option:`direct`\=1 option must be used. fio must also be run as - the root user. - -.. 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:: 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] - - 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:: 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:: 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. - **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. - **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. - -.. 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 - -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= - - 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= - - 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). - - -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` 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:: 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 - - 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. - -.. 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 -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 `cmdprio_percentage` and `hipri_percentage` - 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 `cmdprio_percentage` and - `hipri_percentage` 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`` 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_watermark=int - - The maximum value that the absolute value of the flow counter is allowed to - reach before the job must wait for a lower value of the counter. - -.. option:: flow_sleep=int - - The period of time, in microseconds, to wait after the flow watermark has - been exceeded 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:: - - ---verify.state. - - 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_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:: 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;read_iops;read_runtime_ms;read_slat_min;read_slat_max;read_slat_mean;read_slat_dev;read_clat_min;read_clat_max;read_clat_mean;read_clat_dev;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;read_lat_max;read_lat_mean;read_lat_dev;read_bw_min;read_bw_max;read_bw_agg_pct;read_bw_mean;read_bw_dev;write_kb;write_bandwidth;write_iops;write_runtime_ms;write_slat_min;write_slat_max;write_slat_mean;write_slat_dev;write_clat_min;write_clat_max;write_clat_mean;write_clat_dev;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;write_lat_max;write_lat_mean;write_lat_dev;write_bw_min;write_bw_max;write_bw_agg_pct;write_bw_mean;write_bw_dev;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=":" --merge_blktrace_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=":"" --merge_blktrace_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 --client= - -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= --client= - -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 - -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.