+.. 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 each clone if not specified, but
+ let all clones use the same if set.
+
+ See the :option:`filename` option for information on how to escape "``:``" and
+ "``\``" characters within the directory path itself.
+
+.. 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 and backslash 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.
+
+.. 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:: zonesize=int
+
+ Divide a file into zones of the specified size. See :option:`zoneskip`.
+
+.. option:: zonerange=int
+
+ Give size of an I/O zone. See :option:`zoneskip`.
+
+.. option:: zoneskip=int
+
+ Skip the specified number of bytes when :option:`zonesize` data has been
+ read. The two zone options can be used to only do I/O on zones of a file.
+
+
+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 only).
+ **randread**
+ Random reads.
+ **randwrite**
+ Random writes.
+ **randtrim**
+ Random trims (Linux block devices only).
+ **rw,readwrite**
+ Sequential mixed reads and writes.
+ **randrw**
+ Random mixed reads and writes.
+ **trimwrite**
+ Sequential trim+write sequences. Blocks will be trimmed first,
+ then the same blocks will be written to.
+
+ Fio defaults to read if the option is not specified. For the mixed I/O
+ types, the default is to split them 50/50. For certain types of I/O the
+ result may still be skewed a bit, since the speed may be different.
+
+ It is possible to specify the number of I/Os to do before getting a new
+ offset by appending ``:<nr>`` to the end of the string given. For a
+ random read, it would look like ``rw=randread:8`` for passing in an offset
+ modifier with a value of 8. If the suffix is used with a sequential I/O
+ pattern, then the *<nr>* value specified will be **added** to the generated
+ offset for each I/O turning sequential I/O into sequential I/O with holes.
+ For instance, using ``rw=write:4k`` will skip 4k for every write. Also see
+ the :option:`rw_sequencer` option.
+
+.. option:: rw_sequencer=str
+
+ If an offset modifier is given by appending a number to the ``rw=<str>``
+ line, then this option controls how that number modifies the I/O offset
+ being generated. Accepted values are:
+
+ **sequential**
+ Generate sequential offset.
+ **identical**
+ Generate the same offset.
+
+ ``sequential`` is only useful for random I/O, where fio would normally
+ generate a new random offset for every I/O. If you append e.g. 8 to randread,
+ you would get a new random offset for every 8 I/Os. The result would be a
+ seek for only every 8 I/Os, instead of for every I/O. Use ``rw=randread:8``
+ to specify that. As sequential I/O is already sequential, setting
+ ``sequential`` for that would not result in any differences. ``identical``
+ behaves in a similar fashion, except it sends the same offset 8 number of
+ times before generating a new offset.
+
+.. option:: unified_rw_reporting=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.
+
+ **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 are available, **none** if not.
+
+.. option:: fadvise_hint=str
+
+ Use :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 next ``blockalign``-ed
+ offset will be used. 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_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.
+
+.. 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, and DragonFlyBSD 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
+
+ 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
+
+ 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.
+
+.. 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.
+
+.. 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
+
+.. 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. The default is to only fill it at init time and reuse that
+ data. Only makes sense if zero_buffers isn't specified, naturally. If data
+ verification is enabled, `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 and a fixed pattern. The fixed pattern is either zeros,
+ or the pattern specified by :option:`buffer_pattern`. If the pattern option
+ is used, it might skew the compression ratio slightly. Note that this is per
+ block size unit, for file/disk wide compression level that matches this
+ setting, you'll also want to set :option:`refill_buffers`.
+
+.. option:: buffer_compress_chunk=int
+
+ See :option:`buffer_compress_percentage`. This setting allows fio to manage
+ how big the ranges of random data and zeroed data is. Without this set, fio
+ will provide :option:`buffer_compress_percentage` of blocksize random data,
+ followed by the remaining zeroed. With this set to some chunk size smaller
+ than the block size, fio can alternate random and zeroed data throughout the
+ I/O buffer.
+
+.. 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.
+
+.. 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.
+
+ **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.
+
+ **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`=<nr_of_cpu>
+ to get desired CPU usage, as the cpuload only loads a
+ single CPU at the desired rate. A job never finishes unless there is
+ at least one non-cpuio job.
+
+ **guasi**
+ The GUASI I/O engine is the Generic Userspace Asyncronous 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.
+
+ **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.
+
+ **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.
+
+ **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 NVML
+ libpmemblk library.
+
+ **dev-dax**
+ Read and write using device DAX to a persistent memory device (e.g.,
+ /dev/dax0.0) through the NVML 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.
+
+
+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:: 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:: 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.
+
+.. option:: hostname=str : [netsplice] [net]
+
+ The hostname or IP address to use for TCP or UDP 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]
+
+ Specifies the name of the Ceph cluster.
+
+.. option:: rbdname=str : [rbd]
+
+ Specifies the name of the RBD.
+
+.. option:: pool=str : [rbd]
+
+ Specifies the name of the Ceph pool containing RBD.
+
+.. option:: clientname=str : [rbd]
+
+ 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:: 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.
+
+
+I/O depth
+~~~~~~~~~
+
+.. option:: iodepth=int
+
+ Number of I/O units to keep in flight against the file. Note that
+ increasing *iodepth* beyond 1 will not affect synchronous ioengines (except
+ for small degrees when :option:`verify_async` is in use). Even async
+ engines may impose OS restrictions causing the desired depth not to be
+ achieved. This may happen on Linux when using libaio and not setting
+ :option:`direct`\=1, since buffered I/O is not async on that OS. Keep an
+ eye on the I/O depth distribution in the fio output to verify that the
+ achieved depth is as expected. Default: 1.
+
+.. option:: iodepth_batch_submit=int, iodepth_batch=int
+
+ This defines how many pieces of I/O to submit at once. It defaults to 1
+ which means that we submit each I/O as soon as it is available, but can be
+ raised to submit bigger batches of I/O at the time. If it is set to 0 the
+ :option:`iodepth` value will be used.
+
+.. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int
+
+ This defines how many pieces of I/O to retrieve at once. It defaults to 1
+ which means that we'll ask for a minimum of 1 I/O in the retrieval process
+ from the kernel. The I/O retrieval will go on until we hit the limit set by
+ :option:`iodepth_low`. If this variable is set to 0, then fio will always
+ check for completed events before queuing more I/O. This helps reduce I/O
+ latency, at the cost of more retrieval system calls.
+
+.. option:: iodepth_batch_complete_max=int
+
+ This defines maximum pieces of I/O to retrieve at once. This variable should
+ be used along with :option:`iodepth_batch_complete_min`\=int variable,
+ specifying the range of min and max amount of I/O which should be
+ retrieved. By default it is equal to the :option:`iodepth_batch_complete_min`
+ value.
+
+ Example #1::
+
+ iodepth_batch_complete_min=1
+ iodepth_batch_complete_max=<iodepth>
+
+ which means that we will retrieve at least 1 I/O and up to the whole
+ submitted queue depth. If none of I/O has been completed yet, we will wait.
+
+ Example #2::
+
+ iodepth_batch_complete_min=0
+ iodepth_batch_complete_max=<iodepth>
+
+ which means that we can retrieve up to the whole submitted queue depth, but
+ if none of I/O has been completed yet, we will NOT wait and immediately exit
+ the system call. In this example we simply do polling.
+
+.. option:: iodepth_low=int
+
+ The low water mark indicating when to start filling the queue
+ again. Defaults to the same as :option:`iodepth`, meaning that fio will
+ attempt to keep the queue full at all times. If :option:`iodepth` is set to
+ e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of
+ 16 requests, it will let the depth drain down to 4 before starting to fill
+ it again.
+
+.. option:: serialize_overlap=bool
+
+ Serialize in-flight I/Os that might otherwise cause or suffer from data races.
+ When two or more I/Os are submitted simultaneously, there is no guarantee that
+ the I/Os will be processed or completed in the submitted order. Further, if
+ two or more of those I/Os are writes, any overlapping region between them can
+ become indeterminate/undefined on certain storage. These issues can cause
+ verification to fail erratically when at least one of the racing I/Os is
+ changing data and the overlapping region has a non-zero size. Setting
+ ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
+ serializing in-flight I/Os that have a non-zero overlap. Note that setting
+ this option can reduce both performance and the `:option:iodepth` achieved.
+ Additionally this option does not work when :option:`io_submit_mode` is set to
+ offload. 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.
+
+
+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:: 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 <device> -o /dev/null -d file_for_fio.bin``).
+
+.. 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_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 I/O offsets and lengths in a trace to this power of 2
+ value.
+
+.. option:: replay_scale=int
+
+ Scale sector offsets down by this factor when replaying traces.
+
+
+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.
+
+.. option:: prioclass=int
+
+ Set the I/O priority class. See man :manpage:`ionice(1)`.
+
+.. 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:: cpus_allowed=str
+
+ Controls the same options as :option:`cpumask`, but accepts a textual
+ specification of the permitted CPUs instead. So to use CPUs 1 and 5 you
+ would specify ``cpus_allowed=1,5``. This option also allows a range of CPUs
+ to be specified -- say you wanted a binding to CPUs 1, 5, and 8 to 15, you
+ would set ``cpus_allowed=1,5,8-15``.
+
+.. 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 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:: numa_cpu_nodes=str
+
+ Set this job running on specified NUMA nodes' CPUs. The arguments allow
+ comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable
+ NUMA options support, fio must be built on a system with libnuma-dev(el)
+ installed.
+
+.. option:: numa_mem_policy=str
+
+ Set this job's memory policy and corresponding NUMA nodes. Format of the
+ arguments::
+
+ <mode>[:<nodelist>]
+
+ ``mode`` is one of the following memory poicies: ``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
+ but sometimes this is not the desired action. Setting ``exitall`` will
+ instead make fio terminate all other jobs when one job finishes.
+
+.. 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
+ fatest 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.
+
+.. option:: verifysort=bool
+
+ If true, fio will sort written verify blocks when it deems it faster to read
+ them back in a sorted manner. This is often the case when overwriting an
+ existing file, since the blocks are already laid out in the file system. You
+ can ignore this option unless doing huge amounts of really fast I/O where
+ the red-black tree sorting CPU time becomes significant. Default: true.
+
+.. option:: verifysort_nr=int
+
+ Pre-load and sort verify blocks for a read workload.
+
+.. option:: verify_offset=int
+
+ Swap the verification header with data somewhere else in the block before
+ writing. It is swapped back before verifying.
+
+.. option:: verify_interval=int
+
+ Write the verification header at a finer granularity than the
+ :option:`blocksize`. It will be written for chunks the size of
+ ``verify_interval``. :option:`blocksize` should divide this evenly.
+
+.. option:: verify_pattern=str
+
+ If set, fio will fill the I/O buffers with this pattern. Fio defaults to
+ filling with totally random bytes, but sometimes it's interesting to fill
+ with a known pattern for I/O verification purposes. Depending on the width
+ of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it can
+ be either a decimal or a hex number). The ``verify_pattern`` if larger than
+ a 32-bit quantity has to be a hex number that starts with either "0x" or
+ "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o
+ format, which means that for each block offset will be written and then
+ verified back, e.g.::
+
+ verify_pattern=%o
+
+ Or use combination of everything::
+
+ verify_pattern=0xff%o"abcd"-12
+
+.. option:: verify_fatal=bool
+
+ Normally fio will keep checking the entire contents before quitting on a
+ block verification failure. If this option is set, fio will exit the job on
+ the first observed failure. Default: false.
+
+.. option:: verify_dump=bool
+
+ If set, dump the contents of both the original data block and the data block
+ we read off disk to files. This allows later analysis to inspect just what
+ kind of data corruption occurred. Off by default.
+
+.. option:: verify_async=int
+
+ Fio will normally verify I/O inline from the submitting thread. This option
+ takes an integer describing how many async offload threads to create for I/O
+ verification instead, causing fio to offload the duty of verifying I/O
+ contents to one or more separate threads. If using this offload option, even
+ sync I/O engines can benefit from using an :option:`iodepth` setting higher
+ than 1, as it allows them to have I/O in flight while verifies are running.
+ Defaults to 0 async threads, i.e. verification is not asynchronous.
+
+.. option:: verify_async_cpus=str
+
+ Tell fio to set the given CPU affinity on the async I/O verification
+ threads. See :option:`cpus_allowed` for the format used.
+
+.. option:: verify_backlog=int
+
+ Fio will normally verify the written contents of a job that utilizes verify
+ once that job has completed. In other words, everything is written then
+ everything is read back and verified. You may want to verify continually
+ instead for a variety of reasons. Fio stores the meta data associated with
+ an I/O block in memory, so for large verify workloads, quite a bit of memory
+ would be used up holding this meta data. If this option is enabled, fio will
+ write only N blocks before verifying these blocks.
+
+.. option:: verify_backlog_batch=int
+
+ Control how many blocks fio will verify if :option:`verify_backlog` is
+ set. If not set, will default to the value of :option:`verify_backlog`
+ (meaning the entire queue is read back and verified). If
+ ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all
+ blocks will be verified, if ``verify_backlog_batch`` is larger than
+ :option:`verify_backlog`, some blocks will be verified more than once.
+
+.. option:: verify_state_save=bool
+
+ When a job exits during the write phase of a verify workload, save its
+ current state. This allows fio to replay up until that point, if the verify
+ state is loaded for the verify read phase. The format of the filename is,
+ roughly::
+
+ <type>-<jobname>-<jobindex>-verify.state.
+
+ <type> is "local" for a local run, "sock" for a client/server socket
+ connection, and "ip" (192.168.0.1, for instance) for a networked
+ client/server connection. Defaults to true.
+
+.. option:: verify_state_load=bool
+
+ If a verify termination trigger was used, fio stores the current write state
+ of each thread. This can be used at verification time so that fio knows how
+ far it should verify. Without this information, fio will run a full
+ verification pass, according to the settings in the job file used. Default
+ false.
+
+.. option:: trim_percentage=int
+
+ Number of verify blocks to discard/trim.
+
+.. option:: trim_verify_zero=bool
+
+ Verify that trim/discarded blocks are returned as zeros.
+
+.. option:: trim_backlog=int
+
+ Trim after this number of blocks are written.
+
+.. option:: trim_backlog_batch=int
+
+ Trim this number of I/O blocks.
+
+.. option:: experimental_verify=bool
+
+ Enable experimental verification.
+
+Steady state
+~~~~~~~~~~~~
+
+.. option:: steadystate=str:float, ss=str:float
+
+ Define the criterion and limit for assessing steady state performance. The
+ first parameter designates the criterion whereas the second parameter sets
+ the threshold. When the criterion falls below the threshold for the
+ specified duration, the job will stop. For example, `iops_slope:0.1%` will
+ direct fio to terminate the job when the least squares regression slope
+ falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled
+ this will apply to all jobs in the group. Below is the list of available
+ steady state assessment criteria. All assessments are carried out using only
+ data from the rolling collection window. Threshold limits can be expressed
+ as a fixed value or as a percentage of the mean in the collection window.
+
+ **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. The included
+ :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
+ text files into nice graphs. See :option:`write_lat_log` for behavior of
+ given filename. For this option, the postfix is :file:`_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 job
+ index. See `Log File Formats`_.
+
+.. option:: write_lat_log=str
+
+ Same as :option:`write_bw_log`, except that this option stores I/O
+ submission, completion, and total latencies instead. If no filename is given
+ with this option, the default filename of :file:`jobname_type.log` is
+ used. Even if the filename is given, fio will still append the type of
+ log. So if one specifies::
+
+ write_lat_log=foo
+
+ The actual log names will be :file:`foo_slat.x.log`, :file:`foo_clat.x.log`,
+ and :file:`foo_lat.x.log`, where `x` is the index of the job (`1..N`, where `N`
+ is the number of jobs). This helps :command:`fio_generate_plots` find the
+ logs automatically. If :option:`per_job_logs` is false, then the filename
+ will not include the job index. See `Log File Formats`_.
+
+.. option:: write_hist_log=str
+
+ Same as :option:`write_lat_log`, but writes I/O completion latency
+ histograms. If no filename is given with this option, the default filename
+ of :file:`jobname_clat_hist.x.log` is used, where `x` is the index of the
+ job (`1..N`, where `N` is the number of jobs). Even if the filename is given,
+ fio will still append the type of log. If :option:`per_job_logs` is false,
+ then the filename will not include the job index. See `Log File Formats`_.
+
+.. option:: write_iops_log=str
+
+ Same as :option:`write_bw_log`, but writes IOPS. If no filename is given
+ with this option, the default filename of :file:`jobname_type.x.log` is
+ used, where `x` is the index of the job (`1..N`, where `N` is the number of
+ jobs). Even if the filename is given, fio will still append the type of
+ log. If :option:`per_job_logs` is false, then the filename will not include
+ the job index. See `Log File Formats`_.
+
+.. 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` 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 `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.
+
+.. 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:: clat_percentiles=bool
+
+ Enable the reporting of percentiles of completion latencies.
+
+.. option:: percentile_list=float_list
+
+ Overwrite the default list of percentiles for completion latencies and the
+ block error histogram. Each number is a floating number in the range
+ (0,100], and the maximum length of the list is 20. Use ``:`` to separate the
+ numbers, and list the numbers in ascending order. For example,
+ ``--percentile_list=99.5:99.9`` will cause fio to report the values of
+ completion latency below which 99.5% and 99.9% of the observed latencies
+ fell, respectively.
+
+
+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 `--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.
+
+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
+
+
+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.
+
+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`)
+
+*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 offset, 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`.
+
+Fio defaults to logging every individual I/O. When IOPS are logged for individual
+I/Os the *value* entry will always be 1. If windowed logging is enabled through
+:option:`log_avg_msec`, fio logs the average values over the specified period of time.
+If windowed logging is enabled and :option:`log_max_value` is set, then fio logs
+maximum values in that window instead of averages. Since *data direction*, *block
+size* and *offset* are per-I/O values, if windowed logging is enabled they
+aren't applicable and will be 0.
+
+Client/Server
+-------------
+
+Normally fio is invoked as a stand-alone application on the machine where the
+I/O workload should be generated. However, the backend and frontend of fio can
+be run separately i.e., the fio server can generate an I/O workload on the "Device
+Under Test" while being controlled by a client on another machine.
+
+Start the server on the machine which has access to the storage DUT::
+
+ $ fio --server=args
+
+where `args` defines what fio listens to. The arguments are of the form
+``type,hostname`` or ``IP,port``. *type* is either ``ip`` (or ip4) for TCP/IP
+v4, ``ip6`` for TCP/IP v6, or ``sock`` for a local unix domain socket.
+*hostname* is either a hostname or IP address, and *port* is the port to listen
+to (only valid for TCP/IP, not a local socket). Some examples:
+
+1) ``fio --server``
+
+ Start a fio server, listening on all interfaces on the default port (8765).
+
+2) ``fio --server=ip:hostname,4444``
+
+ Start a fio server, listening on IP belonging to hostname and on port 4444.
+
+3) ``fio --server=ip6:::1,4444``
+
+ Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
+
+4) ``fio --server=,4444``
+
+ Start a fio server, listening on all interfaces on port 4444.
+
+5) ``fio --server=1.2.3.4``
+
+ Start a fio server, listening on IP 1.2.3.4 on the default port.
+
+6) ``fio --server=sock:/tmp/fio.sock``
+
+ Start a fio server, listening on the local socket :file:`/tmp/fio.sock`.
+
+Once a server is running, a "client" can connect to the fio server with::
+
+ fio <local-args> --client=<server> <remote-args> <job file(s)>
+
+where `local-args` are arguments for the client where it is running, `server`
+is the connect string, and `remote-args` and `job file(s)` are sent to the
+server. The `server` string follows the same format as it does on the server
+side, to allow IP/hostname/socket and port strings.