4 The first step in getting fio to simulate a desired I/O workload, is writing a
5 job file describing that specific setup. A job file may contain any number of
6 threads and/or files -- the typical contents of the job file is a *global*
7 section defining shared parameters, and one or more job sections describing the
8 jobs involved. When run, fio parses this file and sets everything up as
9 described. If we break down a job from top to bottom, it contains the following
14 Defines the I/O pattern issued to the file(s). We may only be reading
15 sequentially from this file(s), or we may be writing randomly. Or even
16 mixing reads and writes, sequentially or randomly.
17 Should we be doing buffered I/O, or direct/raw I/O?
21 In how large chunks are we issuing I/O? This may be a single value,
22 or it may describe a range of block sizes.
26 How much data are we going to be reading/writing.
30 How do we issue I/O? We could be memory mapping the file, we could be
31 using regular read/write, we could be using splice, async I/O, or even
36 If the I/O engine is async, how large a queuing depth do we want to
42 How many files are we spreading the workload over.
44 `Threads, processes and job synchronization`_
46 How many threads or processes should we spread this workload over.
48 The above are the basic parameters defined for a workload, in addition there's a
49 multitude of parameters that modify other aspects of how this job behaves.
55 .. option:: --debug=type
57 Enable verbose tracing `type` of various fio actions. May be ``all`` for all types
58 or individual types separated by a comma (e.g. ``--debug=file,mem`` will
59 enable file and memory debugging). Currently, additional logging is
63 Dump info related to processes.
65 Dump info related to file actions.
67 Dump info related to I/O queuing.
69 Dump info related to memory allocations.
71 Dump info related to blktrace setup.
73 Dump info related to I/O verification.
75 Enable all debug options.
77 Dump info related to random offset generation.
79 Dump info related to option matching and parsing.
81 Dump info related to disk utilization updates.
83 Dump info only related to job number x.
85 Dump info only related to mutex up/down ops.
87 Dump info related to profile extensions.
89 Dump info related to internal time keeping.
91 Dump info related to networking connections.
93 Dump info related to I/O rate switching.
95 Dump info related to log compress/decompress.
97 Dump info related to steadystate detection.
99 Dump info related to the helper thread.
101 Dump info related to support for zoned block devices.
103 Show available debug options.
105 .. option:: --parse-only
107 Parse options only, don't start any I/O.
109 .. option:: --merge-blktrace-only
111 Merge blktraces only, don't start any I/O.
113 .. option:: --output=filename
115 Write output to file `filename`.
117 .. option:: --output-format=format
119 Set the reporting `format` to `normal`, `terse`, `json`, or `json+`. Multiple
120 formats can be selected, separated by a comma. `terse` is a CSV based
121 format. `json+` is like `json`, except it adds a full dump of the latency
124 .. option:: --bandwidth-log
126 Generate aggregate bandwidth logs.
128 .. option:: --minimal
130 Print statistics in a terse, semicolon-delimited format.
132 .. option:: --append-terse
134 Print statistics in selected mode AND terse, semicolon-delimited format.
135 **Deprecated**, use :option:`--output-format` instead to select multiple
138 .. option:: --terse-version=version
140 Set terse `version` output format (default 3, or 2 or 4 or 5).
142 .. option:: --version
144 Print version information and exit.
148 Print a summary of the command line options and exit.
150 .. option:: --cpuclock-test
152 Perform test and validation of internal CPU clock.
154 .. option:: --crctest=[test]
156 Test the speed of the built-in checksumming functions. If no argument is
157 given, all of them are tested. Alternatively, a comma separated list can
158 be passed, in which case the given ones are tested.
160 .. option:: --cmdhelp=command
162 Print help information for `command`. May be ``all`` for all commands.
164 .. option:: --enghelp=[ioengine[,command]]
166 List all commands defined by `ioengine`, or print help for `command`
167 defined by `ioengine`. If no `ioengine` is given, list all
170 .. option:: --showcmd=jobfile
172 Convert `jobfile` to a set of command-line options.
174 .. option:: --readonly
176 Turn on safety read-only checks, preventing writes and trims. The
177 ``--readonly`` option is an extra safety guard to prevent users from
178 accidentally starting a write or trim workload when that is not desired.
179 Fio will only modify the device under test if
180 `rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite` is given. This
181 safety net can be used as an extra precaution.
183 .. option:: --eta=when
185 Specifies when real-time ETA estimate should be printed. `when` may be
186 `always`, `never` or `auto`. `auto` is the default, it prints ETA
187 when requested if the output is a TTY. `always` disregards the output
188 type, and prints ETA when requested. `never` never prints ETA.
190 .. option:: --eta-interval=time
192 By default, fio requests client ETA status roughly every second. With
193 this option, the interval is configurable. Fio imposes a minimum
194 allowed time to avoid flooding the console, less than 250 msec is
197 .. option:: --eta-newline=time
199 Force a new line for every `time` period passed. When the unit is omitted,
200 the value is interpreted in seconds.
202 .. option:: --status-interval=time
204 Force a full status dump of cumulative (from job start) values at `time`
205 intervals. This option does *not* provide per-period measurements. So
206 values such as bandwidth are running averages. When the time unit is omitted,
207 `time` is interpreted in seconds. Note that using this option with
208 ``--output-format=json`` will yield output that technically isn't valid
209 json, since the output will be collated sets of valid json. It will need
210 to be split into valid sets of json after the run.
212 .. option:: --section=name
214 Only run specified section `name` in job file. Multiple sections can be specified.
215 The ``--section`` option allows one to combine related jobs into one file.
216 E.g. one job file could define light, moderate, and heavy sections. Tell
217 fio to run only the "heavy" section by giving ``--section=heavy``
218 command line option. One can also specify the "write" operations in one
219 section and "verify" operation in another section. The ``--section`` option
220 only applies to job sections. The reserved *global* section is always
223 .. option:: --alloc-size=kb
225 Allocate additional internal smalloc pools of size `kb` in KiB. The
226 ``--alloc-size`` option increases shared memory set aside for use by fio.
227 If running large jobs with randommap enabled, fio can run out of memory.
228 Smalloc is an internal allocator for shared structures from a fixed size
229 memory pool and can grow to 16 pools. The pool size defaults to 16MiB.
231 NOTE: While running :file:`.fio_smalloc.*` backing store files are visible
234 .. option:: --warnings-fatal
236 All fio parser warnings are fatal, causing fio to exit with an
239 .. option:: --max-jobs=nr
241 Set the maximum number of threads/processes to support to `nr`.
242 NOTE: On Linux, it may be necessary to increase the shared-memory
243 limit (:file:`/proc/sys/kernel/shmmax`) if fio runs into errors while
246 .. option:: --server=args
248 Start a backend server, with `args` specifying what to listen to.
249 See `Client/Server`_ section.
251 .. option:: --daemonize=pidfile
253 Background a fio server, writing the pid to the given `pidfile` file.
255 .. option:: --client=hostname
257 Instead of running the jobs locally, send and run them on the given `hostname`
258 or set of `hostname`\s. See `Client/Server`_ section.
260 .. option:: --remote-config=file
262 Tell fio server to load this local `file`.
264 .. option:: --idle-prof=option
266 Report CPU idleness. `option` is one of the following:
269 Run unit work calibration only and exit.
272 Show aggregate system idleness and unit work.
275 As **system** but also show per CPU idleness.
277 .. option:: --inflate-log=log
279 Inflate and output compressed `log`.
281 .. option:: --trigger-file=file
283 Execute trigger command when `file` exists.
285 .. option:: --trigger-timeout=time
287 Execute trigger at this `time`.
289 .. option:: --trigger=command
291 Set this `command` as local trigger.
293 .. option:: --trigger-remote=command
295 Set this `command` as remote trigger.
297 .. option:: --aux-path=path
299 Use the directory specified by `path` for generated state files instead
300 of the current working directory.
302 Any parameters following the options will be assumed to be job files, unless
303 they match a job file parameter. Multiple job files can be listed and each job
304 file will be regarded as a separate group. Fio will :option:`stonewall`
305 execution between each group.
311 As previously described, fio accepts one or more job files describing what it is
312 supposed to do. The job file format is the classic ini file, where the names
313 enclosed in [] brackets define the job name. You are free to use any ASCII name
314 you want, except *global* which has special meaning. Following the job name is
315 a sequence of zero or more parameters, one per line, that define the behavior of
316 the job. If the first character in a line is a ';' or a '#', the entire line is
317 discarded as a comment.
319 A *global* section sets defaults for the jobs described in that file. A job may
320 override a *global* section parameter, and a job file may even have several
321 *global* sections if so desired. A job is only affected by a *global* section
324 The :option:`--cmdhelp` option also lists all options. If used with a `command`
325 argument, :option:`--cmdhelp` will detail the given `command`.
327 See the `examples/` directory for inspiration on how to write job files. Note
328 the copyright and license requirements currently apply to `examples/` files.
330 So let's look at a really simple job file that defines two processes, each
331 randomly reading from a 128MiB file:
335 ; -- start job file --
346 As you can see, the job file sections themselves are empty as all the described
347 parameters are shared. As no :option:`filename` option is given, fio makes up a
348 `filename` for each of the jobs as it sees fit. On the command line, this job
349 would look as follows::
351 $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
354 Let's look at an example that has a number of processes writing randomly to
359 ; -- start job file --
370 Here we have no *global* section, as we only have one job defined anyway. We
371 want to use async I/O here, with a depth of 4 for each file. We also increased
372 the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical
373 jobs. The result is 4 processes each randomly writing to their own 64MiB
374 file. Instead of using the above job file, you could have given the parameters
375 on the command line. For this case, you would specify::
377 $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
379 When fio is utilized as a basis of any reasonably large test suite, it might be
380 desirable to share a set of standardized settings across multiple job files.
381 Instead of copy/pasting such settings, any section may pull in an external
382 :file:`filename.fio` file with *include filename* directive, as in the following
385 ; -- start job file including.fio --
389 include glob-include.fio
396 include test-include.fio
397 ; -- end job file including.fio --
401 ; -- start job file glob-include.fio --
404 ; -- end job file glob-include.fio --
408 ; -- start job file test-include.fio --
411 ; -- end job file test-include.fio --
413 Settings pulled into a section apply to that section only (except *global*
414 section). Include directives may be nested in that any included file may contain
415 further include directive(s). Include files may not contain [] sections.
418 Environment variables
419 ~~~~~~~~~~~~~~~~~~~~~
421 Fio also supports environment variable expansion in job files. Any sub-string of
422 the form ``${VARNAME}`` as part of an option value (in other words, on the right
423 of the '='), will be expanded to the value of the environment variable called
424 `VARNAME`. If no such environment variable is defined, or `VARNAME` is the
425 empty string, the empty string will be substituted.
427 As an example, let's look at a sample fio invocation and job file::
429 $ SIZE=64m NUMJOBS=4 fio jobfile.fio
433 ; -- start job file --
440 This will expand to the following equivalent job file at runtime:
444 ; -- start job file --
451 Fio ships with a few example job files, you can also look there for inspiration.
456 Additionally, fio has a set of reserved keywords that will be replaced
457 internally with the appropriate value. Those keywords are:
461 The architecture page size of the running system.
465 Megabytes of total memory in the system.
469 Number of online available CPUs.
471 These can be used on the command line or in the job file, and will be
472 automatically substituted with the current system values when the job is
473 run. Simple math is also supported on these keywords, so you can perform actions
478 and get that properly expanded to 8 times the size of memory in the machine.
484 This section describes in details each parameter associated with a job. Some
485 parameters take an option of a given type, such as an integer or a
486 string. Anywhere a numeric value is required, an arithmetic expression may be
487 used, provided it is surrounded by parentheses. Supported operators are:
496 For time values in expressions, units are microseconds by default. This is
497 different than for time values not in expressions (not enclosed in
498 parentheses). The following types are used:
505 String: A sequence of alphanumeric characters.
508 Integer with possible time suffix. Without a unit value is interpreted as
509 seconds unless otherwise specified. Accepts a suffix of 'd' for days, 'h' for
510 hours, 'm' for minutes, 's' for seconds, 'ms' (or 'msec') for milliseconds and
511 'us' (or 'usec') for microseconds. For example, use 10m for 10 minutes.
516 Integer. A whole number value, which may contain an integer prefix
517 and an integer suffix:
519 [*integer prefix*] **number** [*integer suffix*]
521 The optional *integer prefix* specifies the number's base. The default
522 is decimal. *0x* specifies hexadecimal.
524 The optional *integer suffix* specifies the number's units, and includes an
525 optional unit prefix and an optional unit. For quantities of data, the
526 default unit is bytes. For quantities of time, the default unit is seconds
527 unless otherwise specified.
529 With :option:`kb_base`\=1000, fio follows international standards for unit
530 prefixes. To specify power-of-10 decimal values defined in the
531 International System of Units (SI):
533 * *K* -- means kilo (K) or 1000
534 * *M* -- means mega (M) or 1000**2
535 * *G* -- means giga (G) or 1000**3
536 * *T* -- means tera (T) or 1000**4
537 * *P* -- means peta (P) or 1000**5
539 To specify power-of-2 binary values defined in IEC 80000-13:
541 * *Ki* -- means kibi (Ki) or 1024
542 * *Mi* -- means mebi (Mi) or 1024**2
543 * *Gi* -- means gibi (Gi) or 1024**3
544 * *Ti* -- means tebi (Ti) or 1024**4
545 * *Pi* -- means pebi (Pi) or 1024**5
547 For Zone Block Device Mode:
550 With :option:`kb_base`\=1024 (the default), the unit prefixes are opposite
551 from those specified in the SI and IEC 80000-13 standards to provide
552 compatibility with old scripts. For example, 4k means 4096.
554 For quantities of data, an optional unit of 'B' may be included
555 (e.g., 'kB' is the same as 'k').
557 The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega,
558 not milli). 'b' and 'B' both mean byte, not bit.
560 Examples with :option:`kb_base`\=1000:
562 * *4 KiB*: 4096, 4096b, 4096B, 4ki, 4kib, 4kiB, 4Ki, 4KiB
563 * *1 MiB*: 1048576, 1mi, 1024ki
564 * *1 MB*: 1000000, 1m, 1000k
565 * *1 TiB*: 1099511627776, 1ti, 1024gi, 1048576mi
566 * *1 TB*: 1000000000, 1t, 1000m, 1000000k
568 Examples with :option:`kb_base`\=1024 (default):
570 * *4 KiB*: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
571 * *1 MiB*: 1048576, 1m, 1024k
572 * *1 MB*: 1000000, 1mi, 1000ki
573 * *1 TiB*: 1099511627776, 1t, 1024g, 1048576m
574 * *1 TB*: 1000000000, 1ti, 1000mi, 1000000ki
576 To specify times (units are not case sensitive):
580 * *M* -- means minutes
581 * *s* -- or sec means seconds (default)
582 * *ms* -- or *msec* means milliseconds
583 * *us* -- or *usec* means microseconds
585 If the option accepts an upper and lower range, use a colon ':' or
586 minus '-' to separate such values. See :ref:`irange <irange>`.
587 If the lower value specified happens to be larger than the upper value
588 the two values are swapped.
593 Boolean. Usually parsed as an integer, however only defined for
594 true and false (1 and 0).
599 Integer range with suffix. Allows value range to be given, such as
600 1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the
601 option allows two sets of ranges, they can be specified with a ',' or '/'
602 delimiter: 1k-4k/8k-32k. Also see :ref:`int <int>`.
605 A list of floating point numbers, separated by a ':' character.
607 With the above in mind, here follows the complete list of fio job parameters.
613 .. option:: kb_base=int
615 Select the interpretation of unit prefixes in input parameters.
618 Inputs comply with IEC 80000-13 and the International
619 System of Units (SI). Use:
621 - power-of-2 values with IEC prefixes (e.g., KiB)
622 - power-of-10 values with SI prefixes (e.g., kB)
625 Compatibility mode (default). To avoid breaking old scripts:
627 - power-of-2 values with SI prefixes
628 - power-of-10 values with IEC prefixes
630 See :option:`bs` for more details on input parameters.
632 Outputs always use correct prefixes. Most outputs include both
635 bw=2383.3kB/s (2327.4KiB/s)
637 If only one value is reported, then kb_base selects the one to use:
639 **1000** -- SI prefixes
641 **1024** -- IEC prefixes
643 .. option:: unit_base=int
645 Base unit for reporting. Allowed values are:
648 Use auto-detection (default).
660 ASCII name of the job. This may be used to override the name printed by fio
661 for this job. Otherwise the job name is used. On the command line this
662 parameter has the special purpose of also signaling the start of a new job.
664 .. option:: description=str
666 Text description of the job. Doesn't do anything except dump this text
667 description when this job is run. It's not parsed.
669 .. option:: loops=int
671 Run the specified number of iterations of this job. Used to repeat the same
672 workload a given number of times. Defaults to 1.
674 .. option:: numjobs=int
676 Create the specified number of clones of this job. Each clone of job
677 is spawned as an independent thread or process. May be used to setup a
678 larger number of threads/processes doing the same thing. Each thread is
679 reported separately; to see statistics for all clones as a whole, use
680 :option:`group_reporting` in conjunction with :option:`new_group`.
681 See :option:`--max-jobs`. Default: 1.
684 Time related parameters
685 ~~~~~~~~~~~~~~~~~~~~~~~
687 .. option:: runtime=time
689 Tell fio to terminate processing after the specified period of time. It
690 can be quite hard to determine for how long a specified job will run, so
691 this parameter is handy to cap the total runtime to a given time. When
692 the unit is omitted, the value is interpreted in seconds.
694 .. option:: time_based
696 If set, fio will run for the duration of the :option:`runtime` specified
697 even if the file(s) are completely read or written. It will simply loop over
698 the same workload as many times as the :option:`runtime` allows.
700 .. option:: startdelay=irange(time)
702 Delay the start of job for the specified amount of time. Can be a single
703 value or a range. When given as a range, each thread will choose a value
704 randomly from within the range. Value is in seconds if a unit is omitted.
706 .. option:: ramp_time=time
708 If set, fio will run the specified workload for this amount of time before
709 logging any performance numbers. Useful for letting performance settle
710 before logging results, thus minimizing the runtime required for stable
711 results. Note that the ``ramp_time`` is considered lead in time for a job,
712 thus it will increase the total runtime if a special timeout or
713 :option:`runtime` is specified. When the unit is omitted, the value is
716 .. option:: clocksource=str
718 Use the given clocksource as the base of timing. The supported options are:
721 :manpage:`gettimeofday(2)`
724 :manpage:`clock_gettime(2)`
727 Internal CPU clock source
729 cpu is the preferred clocksource if it is reliable, as it is very fast (and
730 fio is heavy on time calls). Fio will automatically use this clocksource if
731 it's supported and considered reliable on the system it is running on,
732 unless another clocksource is specifically set. For x86/x86-64 CPUs, this
733 means supporting TSC Invariant.
735 .. option:: gtod_reduce=bool
737 Enable all of the :manpage:`gettimeofday(2)` reducing options
738 (:option:`disable_clat`, :option:`disable_slat`, :option:`disable_bw_measurement`) plus
739 reduce precision of the timeout somewhat to really shrink the
740 :manpage:`gettimeofday(2)` call count. With this option enabled, we only do
741 about 0.4% of the :manpage:`gettimeofday(2)` calls we would have done if all
742 time keeping was enabled.
744 .. option:: gtod_cpu=int
746 Sometimes it's cheaper to dedicate a single thread of execution to just
747 getting the current time. Fio (and databases, for instance) are very
748 intensive on :manpage:`gettimeofday(2)` calls. With this option, you can set
749 one CPU aside for doing nothing but logging current time to a shared memory
750 location. Then the other threads/processes that run I/O workloads need only
751 copy that segment, instead of entering the kernel with a
752 :manpage:`gettimeofday(2)` call. The CPU set aside for doing these time
753 calls will be excluded from other uses. Fio will manually clear it from the
754 CPU mask of other jobs.
760 .. option:: directory=str
762 Prefix filenames with this directory. Used to place files in a different
763 location than :file:`./`. You can specify a number of directories by
764 separating the names with a ':' character. These directories will be
765 assigned equally distributed to job clones created by :option:`numjobs` as
766 long as they are using generated filenames. If specific `filename(s)` are
767 set fio will use the first listed directory, and thereby matching the
768 `filename` semantic (which generates a file for each clone if not
769 specified, but lets all clones use the same file if set).
771 See the :option:`filename` option for information on how to escape "``:``"
772 characters within the directory path itself.
774 Note: To control the directory fio will use for internal state files
775 use :option:`--aux-path`.
777 .. option:: filename=str
779 Fio normally makes up a `filename` based on the job name, thread number, and
780 file number (see :option:`filename_format`). If you want to share files
781 between threads in a job or several
782 jobs with fixed file paths, specify a `filename` for each of them to override
783 the default. If the ioengine is file based, you can specify a number of files
784 by separating the names with a ':' colon. So if you wanted a job to open
785 :file:`/dev/sda` and :file:`/dev/sdb` as the two working files, you would use
786 ``filename=/dev/sda:/dev/sdb``. This also means that whenever this option is
787 specified, :option:`nrfiles` is ignored. The size of regular files specified
788 by this option will be :option:`size` divided by number of files unless an
789 explicit size is specified by :option:`filesize`.
791 Each colon in the wanted path must be escaped with a ``\``
792 character. For instance, if the path is :file:`/dev/dsk/foo@3,0:c` then you
793 would use ``filename=/dev/dsk/foo@3,0\:c`` and if the path is
794 :file:`F:\\filename` then you would use ``filename=F\:\filename``.
796 On Windows, disk devices are accessed as :file:`\\\\.\\PhysicalDrive0` for
797 the first device, :file:`\\\\.\\PhysicalDrive1` for the second etc.
798 Note: Windows and FreeBSD prevent write access to areas
799 of the disk containing in-use data (e.g. filesystems).
801 The filename "`-`" is a reserved name, meaning *stdin* or *stdout*. Which
802 of the two depends on the read/write direction set.
804 .. option:: filename_format=str
806 If sharing multiple files between jobs, it is usually necessary to have fio
807 generate the exact names that you want. By default, fio will name a file
808 based on the default file format specification of
809 :file:`jobname.jobnumber.filenumber`. With this option, that can be
810 customized. Fio will recognize and replace the following keywords in this
814 The name of the worker thread or process.
816 IP of the fio process when using client/server mode.
818 The incremental number of the worker thread or process.
820 The incremental number of the file for that worker thread or
823 To have dependent jobs share a set of files, this option can be set to have
824 fio generate filenames that are shared between the two. For instance, if
825 :file:`testfiles.$filenum` is specified, file number 4 for any job will be
826 named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
827 will be used if no other format specifier is given.
829 If you specify a path then the directories will be created up to the
830 main directory for the file. So for example if you specify
831 ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
832 created before the file setup part of the job. If you specify
833 :option:`directory` then the path will be relative that directory,
834 otherwise it is treated as the absolute path.
836 .. option:: unique_filename=bool
838 To avoid collisions between networked clients, fio defaults to prefixing any
839 generated filenames (with a directory specified) with the source of the
840 client connecting. To disable this behavior, set this option to 0.
842 .. option:: opendir=str
844 Recursively open any files below directory `str`.
846 .. option:: lockfile=str
848 Fio defaults to not locking any files before it does I/O to them. If a file
849 or file descriptor is shared, fio can serialize I/O to that file to make the
850 end result consistent. This is usual for emulating real workloads that share
851 files. The lock modes are:
854 No locking. The default.
856 Only one thread or process may do I/O at a time, excluding all
859 Read-write locking on the file. Many readers may
860 access the file at the same time, but writes get exclusive access.
862 .. option:: nrfiles=int
864 Number of files to use for this job. Defaults to 1. The size of files
865 will be :option:`size` divided by this unless explicit size is specified by
866 :option:`filesize`. Files are created for each thread separately, and each
867 file will have a file number within its name by default, as explained in
868 :option:`filename` section.
871 .. option:: openfiles=int
873 Number of files to keep open at the same time. Defaults to the same as
874 :option:`nrfiles`, can be set smaller to limit the number simultaneous
877 .. option:: file_service_type=str
879 Defines how fio decides which file from a job to service next. The following
883 Choose a file at random.
886 Round robin over opened files. This is the default.
889 Finish one file before moving on to the next. Multiple files can
890 still be open depending on :option:`openfiles`.
893 Use a *Zipf* distribution to decide what file to access.
896 Use a *Pareto* distribution to decide what file to access.
899 Use a *Gaussian* (normal) distribution to decide what file to
905 For *random*, *roundrobin*, and *sequential*, a postfix can be appended to
906 tell fio how many I/Os to issue before switching to a new file. For example,
907 specifying ``file_service_type=random:8`` would cause fio to issue
908 8 I/Os before selecting a new file at random. For the non-uniform
909 distributions, a floating point postfix can be given to influence how the
910 distribution is skewed. See :option:`random_distribution` for a description
911 of how that would work.
913 .. option:: ioscheduler=str
915 Attempt to switch the device hosting the file to the specified I/O scheduler
918 .. option:: create_serialize=bool
920 If true, serialize the file creation for the jobs. This may be handy to
921 avoid interleaving of data files, which may greatly depend on the filesystem
922 used and even the number of processors in the system. Default: true.
924 .. option:: create_fsync=bool
926 :manpage:`fsync(2)` the data file after creation. This is the default.
928 .. option:: create_on_open=bool
930 If true, don't pre-create files but allow the job's open() to create a file
931 when it's time to do I/O. Default: false -- pre-create all necessary files
934 .. option:: create_only=bool
936 If true, fio will only run the setup phase of the job. If files need to be
937 laid out or updated on disk, only that will be done -- the actual job contents
938 are not executed. Default: false.
940 .. option:: allow_file_create=bool
942 If true, fio is permitted to create files as part of its workload. If this
943 option is false, then fio will error out if
944 the files it needs to use don't already exist. Default: true.
946 .. option:: allow_mounted_write=bool
948 If this isn't set, fio will abort jobs that are destructive (e.g. that write)
949 to what appears to be a mounted device or partition. This should help catch
950 creating inadvertently destructive tests, not realizing that the test will
951 destroy data on the mounted file system. Note that some platforms don't allow
952 writing against a mounted device regardless of this option. Default: false.
954 .. option:: pre_read=bool
956 If this is given, files will be pre-read into memory before starting the
957 given I/O operation. This will also clear the :option:`invalidate` flag,
958 since it is pointless to pre-read and then drop the cache. This will only
959 work for I/O engines that are seek-able, since they allow you to read the
960 same data multiple times. Thus it will not work on non-seekable I/O engines
961 (e.g. network, splice). Default: false.
963 .. option:: unlink=bool
965 Unlink the job files when done. Not the default, as repeated runs of that
966 job would then waste time recreating the file set again and again. Default:
969 .. option:: unlink_each_loop=bool
971 Unlink job files after each iteration or loop. Default: false.
973 .. option:: zonemode=str
978 The :option:`zonerange`, :option:`zonesize`,
979 :option `zonecapacity` and option:`zoneskip`
980 parameters are ignored.
982 I/O happens in a single zone until
983 :option:`zonesize` bytes have been transferred.
984 After that number of bytes has been
985 transferred processing of the next zone
986 starts. :option `zonecapacity` is ignored.
988 Zoned block device mode. I/O happens
989 sequentially in each zone, even if random I/O
990 has been selected. Random I/O happens across
991 all zones instead of being restricted to a
992 single zone. The :option:`zoneskip` parameter
993 is ignored. :option:`zonerange` and
994 :option:`zonesize` must be identical.
995 Trim is handled using a zone reset operation.
996 Trim only considers non-empty sequential write
997 required and sequential write preferred zones.
999 .. option:: zonerange=int
1001 Size of a single zone. See also :option:`zonesize` and
1004 .. option:: zonesize=int
1006 For :option:`zonemode` =strided, this is the number of bytes to
1007 transfer before skipping :option:`zoneskip` bytes. If this parameter
1008 is smaller than :option:`zonerange` then only a fraction of each zone
1009 with :option:`zonerange` bytes will be accessed. If this parameter is
1010 larger than :option:`zonerange` then each zone will be accessed
1011 multiple times before skipping to the next zone.
1013 For :option:`zonemode` =zbd, this is the size of a single zone. The
1014 :option:`zonerange` parameter is ignored in this mode.
1017 .. option:: zonecapacity=int
1019 For :option:`zonemode` =zbd, this defines the capacity of a single zone,
1020 which is the accessible area starting from the zone start address.
1021 This parameter only applies when using :option:`zonemode` =zbd in
1022 combination with regular block devices. If not specified it defaults to
1023 the zone size. If the target device is a zoned block device, the zone
1024 capacity is obtained from the device information and this option is
1027 .. option:: zoneskip=int
1029 For :option:`zonemode` =strided, the number of bytes to skip after
1030 :option:`zonesize` bytes of data have been transferred. This parameter
1031 must be zero for :option:`zonemode` =zbd.
1033 .. option:: read_beyond_wp=bool
1035 This parameter applies to :option:`zonemode` =zbd only.
1037 Zoned block devices are block devices that consist of multiple zones.
1038 Each zone has a type, e.g. conventional or sequential. A conventional
1039 zone can be written at any offset that is a multiple of the block
1040 size. Sequential zones must be written sequentially. The position at
1041 which a write must occur is called the write pointer. A zoned block
1042 device can be either drive managed, host managed or host aware. For
1043 host managed devices the host must ensure that writes happen
1044 sequentially. Fio recognizes host managed devices and serializes
1045 writes to sequential zones for these devices.
1047 If a read occurs in a sequential zone beyond the write pointer then
1048 the zoned block device will complete the read without reading any data
1049 from the storage medium. Since such reads lead to unrealistically high
1050 bandwidth and IOPS numbers fio only reads beyond the write pointer if
1051 explicitly told to do so. Default: false.
1053 .. option:: max_open_zones=int
1055 When running a random write test across an entire drive many more
1056 zones will be open than in a typical application workload. Hence this
1057 command line option that allows to limit the number of open zones. The
1058 number of open zones is defined as the number of zones to which write
1059 commands are issued.
1061 .. option:: job_max_open_zones=int
1063 Limit on the number of simultaneously opened zones per single
1066 .. option:: ignore_zone_limits=bool
1068 If this option is used, fio will ignore the maximum number of open
1069 zones limit of the zoned block device in use, thus allowing the
1070 option :option:`max_open_zones` value to be larger than the device
1071 reported limit. Default: false.
1073 .. option:: zone_reset_threshold=float
1075 A number between zero and one that indicates the ratio of logical
1076 blocks with data to the total number of logical blocks in the test
1077 above which zones should be reset periodically.
1079 .. option:: zone_reset_frequency=float
1081 A number between zero and one that indicates how often a zone reset
1082 should be issued if the zone reset threshold has been exceeded. A zone
1083 reset is submitted after each (1 / zone_reset_frequency) write
1084 requests. This and the previous parameter can be used to simulate
1085 garbage collection activity.
1091 .. option:: direct=bool
1093 If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that
1094 OpenBSD and ZFS on Solaris don't support direct I/O. On Windows the synchronous
1095 ioengines don't support direct I/O. Default: false.
1097 .. option:: atomic=bool
1099 If value is true, attempt to use atomic direct I/O. Atomic writes are
1100 guaranteed to be stable once acknowledged by the operating system. Only
1101 Linux supports O_ATOMIC right now.
1103 .. option:: buffered=bool
1105 If value is true, use buffered I/O. This is the opposite of the
1106 :option:`direct` option. Defaults to true.
1108 .. option:: readwrite=str, rw=str
1110 Type of I/O pattern. Accepted values are:
1117 Sequential trims (Linux block devices and SCSI
1118 character devices only).
1124 Random trims (Linux block devices and SCSI
1125 character devices only).
1127 Sequential mixed reads and writes.
1129 Random mixed reads and writes.
1131 Sequential trim+write sequences. Blocks will be trimmed first,
1132 then the same blocks will be written to.
1134 Fio defaults to read if the option is not specified. For the mixed I/O
1135 types, the default is to split them 50/50. For certain types of I/O the
1136 result may still be skewed a bit, since the speed may be different.
1138 It is possible to specify the number of I/Os to do before getting a new
1139 offset by appending ``:<nr>`` to the end of the string given. For a
1140 random read, it would look like ``rw=randread:8`` for passing in an offset
1141 modifier with a value of 8. If the suffix is used with a sequential I/O
1142 pattern, then the *<nr>* value specified will be **added** to the generated
1143 offset for each I/O turning sequential I/O into sequential I/O with holes.
1144 For instance, using ``rw=write:4k`` will skip 4k for every write. Also see
1145 the :option:`rw_sequencer` option.
1147 .. option:: rw_sequencer=str
1149 If an offset modifier is given by appending a number to the ``rw=<str>``
1150 line, then this option controls how that number modifies the I/O offset
1151 being generated. Accepted values are:
1154 Generate sequential offset.
1156 Generate the same offset.
1158 ``sequential`` is only useful for random I/O, where fio would normally
1159 generate a new random offset for every I/O. If you append e.g. 8 to randread,
1160 you would get a new random offset for every 8 I/Os. The result would be a
1161 seek for only every 8 I/Os, instead of for every I/O. Use ``rw=randread:8``
1162 to specify that. As sequential I/O is already sequential, setting
1163 ``sequential`` for that would not result in any differences. ``identical``
1164 behaves in a similar fashion, except it sends the same offset 8 number of
1165 times before generating a new offset.
1167 .. option:: unified_rw_reporting=str
1169 Fio normally reports statistics on a per data direction basis, meaning that
1170 reads, writes, and trims are accounted and reported separately. This option
1171 determines whether fio reports the results normally, summed together, or as
1173 Accepted values are:
1176 Normal statistics reporting.
1179 Statistics are summed per data direction and reported together.
1182 Statistics are reported normally, followed by the mixed statistics.
1185 Backward-compatible alias for **none**.
1188 Backward-compatible alias for **mixed**.
1193 .. option:: randrepeat=bool
1195 Seed the random number generator used for random I/O patterns in a
1196 predictable way so the pattern is repeatable across runs. Default: true.
1198 .. option:: allrandrepeat=bool
1200 Seed all random number generators in a predictable way so results are
1201 repeatable across runs. Default: false.
1203 .. option:: randseed=int
1205 Seed the random number generators based on this seed value, to be able to
1206 control what sequence of output is being generated. If not set, the random
1207 sequence depends on the :option:`randrepeat` setting.
1209 .. option:: fallocate=str
1211 Whether pre-allocation is performed when laying down files.
1212 Accepted values are:
1215 Do not pre-allocate space.
1218 Use a platform's native pre-allocation call but fall back to
1219 **none** behavior if it fails/is not implemented.
1222 Pre-allocate via :manpage:`posix_fallocate(3)`.
1225 Pre-allocate via :manpage:`fallocate(2)` with
1226 FALLOC_FL_KEEP_SIZE set.
1229 Extend file to final size via :manpage:`ftruncate(2)`
1230 instead of allocating.
1233 Backward-compatible alias for **none**.
1236 Backward-compatible alias for **posix**.
1238 May not be available on all supported platforms. **keep** is only available
1239 on Linux. If using ZFS on Solaris this cannot be set to **posix**
1240 because ZFS doesn't support pre-allocation. Default: **native** if any
1241 pre-allocation methods except **truncate** are available, **none** if not.
1243 Note that using **truncate** on Windows will interact surprisingly
1244 with non-sequential write patterns. When writing to a file that has
1245 been extended by setting the end-of-file information, Windows will
1246 backfill the unwritten portion of the file up to that offset with
1247 zeroes before issuing the new write. This means that a single small
1248 write to the end of an extended file will stall until the entire
1249 file has been filled with zeroes.
1251 .. option:: fadvise_hint=str
1253 Use :manpage:`posix_fadvise(2)` or :manpage:`posix_fadvise(2)` to
1254 advise the kernel on what I/O patterns are likely to be issued.
1255 Accepted values are:
1258 Backwards-compatible hint for "no hint".
1261 Backwards compatible hint for "advise with fio workload type". This
1262 uses **FADV_RANDOM** for a random workload, and **FADV_SEQUENTIAL**
1263 for a sequential workload.
1266 Advise using **FADV_SEQUENTIAL**.
1269 Advise using **FADV_RANDOM**.
1271 .. option:: write_hint=str
1273 Use :manpage:`fcntl(2)` to advise the kernel what life time to expect
1274 from a write. Only supported on Linux, as of version 4.13. Accepted
1278 No particular life time associated with this file.
1281 Data written to this file has a short life time.
1284 Data written to this file has a medium life time.
1287 Data written to this file has a long life time.
1290 Data written to this file has a very long life time.
1292 The values are all relative to each other, and no absolute meaning
1293 should be associated with them.
1295 .. option:: offset=int
1297 Start I/O at the provided offset in the file, given as either a fixed size in
1298 bytes, zones or a percentage. If a percentage is given, the generated offset will be
1299 aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
1300 provided. Data before the given offset will not be touched. This
1301 effectively caps the file size at `real_size - offset`. Can be combined with
1302 :option:`size` to constrain the start and end range of the I/O workload.
1303 A percentage can be specified by a number between 1 and 100 followed by '%',
1304 for example, ``offset=20%`` to specify 20%. In ZBD mode, value can be set as
1305 number of zones using 'z'.
1307 .. option:: offset_align=int
1309 If set to non-zero value, the byte offset generated by a percentage ``offset``
1310 is aligned upwards to this value. Defaults to 0 meaning that a percentage
1311 offset is aligned to the minimum block size.
1313 .. option:: offset_increment=int
1315 If this is provided, then the real offset becomes `offset + offset_increment
1316 * thread_number`, where the thread number is a counter that starts at 0 and
1317 is incremented for each sub-job (i.e. when :option:`numjobs` option is
1318 specified). This option is useful if there are several jobs which are
1319 intended to operate on a file in parallel disjoint segments, with even
1320 spacing between the starting points. Percentages can be used for this option.
1321 If a percentage is given, the generated offset will be aligned to the minimum
1322 ``blocksize`` or to the value of ``offset_align`` if provided. In ZBD mode, value can
1323 also be set as number of zones using 'z'.
1325 .. option:: number_ios=int
1327 Fio will normally perform I/Os until it has exhausted the size of the region
1328 set by :option:`size`, or if it exhaust the allocated time (or hits an error
1329 condition). With this setting, the range/size can be set independently of
1330 the number of I/Os to perform. When fio reaches this number, it will exit
1331 normally and report status. Note that this does not extend the amount of I/O
1332 that will be done, it will only stop fio if this condition is met before
1333 other end-of-job criteria.
1335 .. option:: fsync=int
1337 If writing to a file, issue an :manpage:`fsync(2)` (or its equivalent) of
1338 the dirty data for every number of blocks given. For example, if you give 32
1339 as a parameter, fio will sync the file after every 32 writes issued. If fio is
1340 using non-buffered I/O, we may not sync the file. The exception is the sg
1341 I/O engine, which synchronizes the disk cache anyway. Defaults to 0, which
1342 means fio does not periodically issue and wait for a sync to complete. Also
1343 see :option:`end_fsync` and :option:`fsync_on_close`.
1345 .. option:: fdatasync=int
1347 Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and
1348 not metadata blocks. In Windows, DragonFlyBSD or OSX there is no
1349 :manpage:`fdatasync(2)` so this falls back to using :manpage:`fsync(2)`.
1350 Defaults to 0, which means fio does not periodically issue and wait for a
1351 data-only sync to complete.
1353 .. option:: write_barrier=int
1355 Make every `N-th` write a barrier write.
1357 .. option:: sync_file_range=str:int
1359 Use :manpage:`sync_file_range(2)` for every `int` number of write
1360 operations. Fio will track range of writes that have happened since the last
1361 :manpage:`sync_file_range(2)` call. `str` can currently be one or more of:
1364 SYNC_FILE_RANGE_WAIT_BEFORE
1366 SYNC_FILE_RANGE_WRITE
1368 SYNC_FILE_RANGE_WAIT_AFTER
1370 So if you do ``sync_file_range=wait_before,write:8``, fio would use
1371 ``SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE`` for every 8
1372 writes. Also see the :manpage:`sync_file_range(2)` man page. This option is
1375 .. option:: overwrite=bool
1377 If true, writes to a file will always overwrite existing data. If the file
1378 doesn't already exist, it will be created before the write phase begins. If
1379 the file exists and is large enough for the specified write phase, nothing
1380 will be done. Default: false.
1382 .. option:: end_fsync=bool
1384 If true, :manpage:`fsync(2)` file contents when a write stage has completed.
1387 .. option:: fsync_on_close=bool
1389 If true, fio will :manpage:`fsync(2)` a dirty file on close. This differs
1390 from :option:`end_fsync` in that it will happen on every file close, not
1391 just at the end of the job. Default: false.
1393 .. option:: rwmixread=int
1395 Percentage of a mixed workload that should be reads. Default: 50.
1397 .. option:: rwmixwrite=int
1399 Percentage of a mixed workload that should be writes. If both
1400 :option:`rwmixread` and :option:`rwmixwrite` is given and the values do not
1401 add up to 100%, the latter of the two will be used to override the
1402 first. This may interfere with a given rate setting, if fio is asked to
1403 limit reads or writes to a certain rate. If that is the case, then the
1404 distribution may be skewed. Default: 50.
1406 .. option:: random_distribution=str:float[:float][,str:float][,str:float]
1408 By default, fio will use a completely uniform random distribution when asked
1409 to perform random I/O. Sometimes it is useful to skew the distribution in
1410 specific ways, ensuring that some parts of the data is more hot than others.
1411 fio includes the following distribution models:
1414 Uniform random distribution
1423 Normal (Gaussian) distribution
1426 Zoned random distribution
1429 Zone absolute random distribution
1431 When using a **zipf** or **pareto** distribution, an input value is also
1432 needed to define the access pattern. For **zipf**, this is the `Zipf
1433 theta`. For **pareto**, it's the `Pareto power`. Fio includes a test
1434 program, :command:`fio-genzipf`, that can be used visualize what the given input
1435 values will yield in terms of hit rates. If you wanted to use **zipf** with
1436 a `theta` of 1.2, you would use ``random_distribution=zipf:1.2`` as the
1437 option. If a non-uniform model is used, fio will disable use of the random
1438 map. For the **normal** distribution, a normal (Gaussian) deviation is
1439 supplied as a value between 0 and 100.
1441 The second, optional float is allowed for **pareto**, **zipf** and **normal** distributions.
1442 It allows to set base of distribution in non-default place, giving more control
1443 over most probable outcome. This value is in range [0-1] which maps linearly to
1444 range of possible random values.
1445 Defaults are: random for **pareto** and **zipf**, and 0.5 for **normal**.
1446 If you wanted to use **zipf** with a `theta` of 1.2 centered on 1/4 of allowed value range,
1447 you would use ``random_distribution=zipf:1.2:0.25``.
1449 For a **zoned** distribution, fio supports specifying percentages of I/O
1450 access that should fall within what range of the file or device. For
1451 example, given a criteria of:
1453 * 60% of accesses should be to the first 10%
1454 * 30% of accesses should be to the next 20%
1455 * 8% of accesses should be to the next 30%
1456 * 2% of accesses should be to the next 40%
1458 we can define that through zoning of the random accesses. For the above
1459 example, the user would do::
1461 random_distribution=zoned:60/10:30/20:8/30:2/40
1463 A **zoned_abs** distribution works exactly like the **zoned**, except
1464 that it takes absolute sizes. For example, let's say you wanted to
1465 define access according to the following criteria:
1467 * 60% of accesses should be to the first 20G
1468 * 30% of accesses should be to the next 100G
1469 * 10% of accesses should be to the next 500G
1471 we can define an absolute zoning distribution with:
1473 random_distribution=zoned_abs=60/20G:30/100G:10/500g
1475 For both **zoned** and **zoned_abs**, fio supports defining up to
1478 Similarly to how :option:`bssplit` works for setting ranges and
1479 percentages of block sizes. Like :option:`bssplit`, it's possible to
1480 specify separate zones for reads, writes, and trims. If just one set
1481 is given, it'll apply to all of them. This goes for both **zoned**
1482 **zoned_abs** distributions.
1484 .. option:: percentage_random=int[,int][,int]
1486 For a random workload, set how big a percentage should be random. This
1487 defaults to 100%, in which case the workload is fully random. It can be set
1488 from anywhere from 0 to 100. Setting it to 0 would make the workload fully
1489 sequential. Any setting in between will result in a random mix of sequential
1490 and random I/O, at the given percentages. Comma-separated values may be
1491 specified for reads, writes, and trims as described in :option:`blocksize`.
1493 .. option:: norandommap
1495 Normally fio will cover every block of the file when doing random I/O. If
1496 this option is given, fio will just get a new random offset without looking
1497 at past I/O history. This means that some blocks may not be read or written,
1498 and that some blocks may be read/written more than once. If this option is
1499 used with :option:`verify` and multiple blocksizes (via :option:`bsrange`),
1500 only intact blocks are verified, i.e., partially-overwritten blocks are
1501 ignored. With an async I/O engine and an I/O depth > 1, it is possible for
1502 the same block to be overwritten, which can cause verification errors. Either
1503 do not use norandommap in this case, or also use the lfsr random generator.
1505 .. option:: softrandommap=bool
1507 See :option:`norandommap`. If fio runs with the random block map enabled and
1508 it fails to allocate the map, if this option is set it will continue without
1509 a random block map. As coverage will not be as complete as with random maps,
1510 this option is disabled by default.
1512 .. option:: random_generator=str
1514 Fio supports the following engines for generating I/O offsets for random I/O:
1517 Strong 2^88 cycle random number generator.
1519 Linear feedback shift register generator.
1521 Strong 64-bit 2^258 cycle random number generator.
1523 **tausworthe** is a strong random number generator, but it requires tracking
1524 on the side if we want to ensure that blocks are only read or written
1525 once. **lfsr** guarantees that we never generate the same offset twice, and
1526 it's also less computationally expensive. It's not a true random generator,
1527 however, though for I/O purposes it's typically good enough. **lfsr** only
1528 works with single block sizes, not with workloads that use multiple block
1529 sizes. If used with such a workload, fio may read or write some blocks
1530 multiple times. The default value is **tausworthe**, unless the required
1531 space exceeds 2^32 blocks. If it does, then **tausworthe64** is
1532 selected automatically.
1538 .. option:: blocksize=int[,int][,int], bs=int[,int][,int]
1540 The block size in bytes used for I/O units. Default: 4096. A single value
1541 applies to reads, writes, and trims. Comma-separated values may be
1542 specified for reads, writes, and trims. A value not terminated in a comma
1543 applies to subsequent types.
1548 means 256k for reads, writes and trims.
1551 means 8k for reads, 32k for writes and trims.
1554 means 8k for reads, 32k for writes, and default for trims.
1557 means default for reads, 8k for writes and trims.
1560 means default for reads, 8k for writes, and default for trims.
1562 .. option:: blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
1564 A range of block sizes in bytes for I/O units. The issued I/O unit will
1565 always be a multiple of the minimum size, unless
1566 :option:`blocksize_unaligned` is set.
1568 Comma-separated ranges may be specified for reads, writes, and trims as
1569 described in :option:`blocksize`.
1571 Example: ``bsrange=1k-4k,2k-8k``.
1573 .. option:: bssplit=str[,str][,str]
1575 Sometimes you want even finer grained control of the block sizes
1576 issued, not just an even split between them. This option allows you to
1577 weight various block sizes, so that you are able to define a specific
1578 amount of block sizes issued. The format for this option is::
1580 bssplit=blocksize/percentage:blocksize/percentage
1582 for as many block sizes as needed. So if you want to define a workload
1583 that has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you would
1586 bssplit=4k/10:64k/50:32k/40
1588 Ordering does not matter. If the percentage is left blank, fio will
1589 fill in the remaining values evenly. So a bssplit option like this one::
1591 bssplit=4k/50:1k/:32k/
1593 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always
1594 add up to 100, if bssplit is given a range that adds up to more, it
1597 Comma-separated values may be specified for reads, writes, and trims as
1598 described in :option:`blocksize`.
1600 If you want a workload that has 50% 2k reads and 50% 4k reads, while
1601 having 90% 4k writes and 10% 8k writes, you would specify::
1603 bssplit=2k/50:4k/50,4k/90:8k/10
1605 Fio supports defining up to 64 different weights for each data
1608 .. option:: blocksize_unaligned, bs_unaligned
1610 If set, fio will issue I/O units with any size within
1611 :option:`blocksize_range`, not just multiples of the minimum size. This
1612 typically won't work with direct I/O, as that normally requires sector
1615 .. option:: bs_is_seq_rand=bool
1617 If this option is set, fio will use the normal read,write blocksize settings
1618 as sequential,random blocksize settings instead. Any random read or write
1619 will use the WRITE blocksize settings, and any sequential read or write will
1620 use the READ blocksize settings.
1622 .. option:: blockalign=int[,int][,int], ba=int[,int][,int]
1624 Boundary to which fio will align random I/O units. Default:
1625 :option:`blocksize`. Minimum alignment is typically 512b for using direct
1626 I/O, though it usually depends on the hardware block size. This option is
1627 mutually exclusive with using a random map for files, so it will turn off
1628 that option. Comma-separated values may be specified for reads, writes, and
1629 trims as described in :option:`blocksize`.
1635 .. option:: zero_buffers
1637 Initialize buffers with all zeros. Default: fill buffers with random data.
1639 .. option:: refill_buffers
1641 If this option is given, fio will refill the I/O buffers on every
1642 submit. Only makes sense if :option:`zero_buffers` isn't specified,
1643 naturally. Defaults to being unset i.e., the buffer is only filled at
1644 init time and the data in it is reused when possible but if any of
1645 :option:`verify`, :option:`buffer_compress_percentage` or
1646 :option:`dedupe_percentage` are enabled then `refill_buffers` is also
1647 automatically enabled.
1649 .. option:: scramble_buffers=bool
1651 If :option:`refill_buffers` is too costly and the target is using data
1652 deduplication, then setting this option will slightly modify the I/O buffer
1653 contents to defeat normal de-dupe attempts. This is not enough to defeat
1654 more clever block compression attempts, but it will stop naive dedupe of
1655 blocks. Default: true.
1657 .. option:: buffer_compress_percentage=int
1659 If this is set, then fio will attempt to provide I/O buffer content
1660 (on WRITEs) that compresses to the specified level. Fio does this by
1661 providing a mix of random data followed by fixed pattern data. The
1662 fixed pattern is either zeros, or the pattern specified by
1663 :option:`buffer_pattern`. If the `buffer_pattern` option is used, it
1664 might skew the compression ratio slightly. Setting
1665 `buffer_compress_percentage` to a value other than 100 will also
1666 enable :option:`refill_buffers` in order to reduce the likelihood that
1667 adjacent blocks are so similar that they over compress when seen
1668 together. See :option:`buffer_compress_chunk` for how to set a finer or
1669 coarser granularity for the random/fixed data region. Defaults to unset
1670 i.e., buffer data will not adhere to any compression level.
1672 .. option:: buffer_compress_chunk=int
1674 This setting allows fio to manage how big the random/fixed data region
1675 is when using :option:`buffer_compress_percentage`. When
1676 `buffer_compress_chunk` is set to some non-zero value smaller than the
1677 block size, fio can repeat the random/fixed region throughout the I/O
1678 buffer at the specified interval (which particularly useful when
1679 bigger block sizes are used for a job). When set to 0, fio will use a
1680 chunk size that matches the block size resulting in a single
1681 random/fixed region within the I/O buffer. Defaults to 512. When the
1682 unit is omitted, the value is interpreted in bytes.
1684 .. option:: buffer_pattern=str
1686 If set, fio will fill the I/O buffers with this pattern or with the contents
1687 of a file. If not set, the contents of I/O buffers are defined by the other
1688 options related to buffer contents. The setting can be any pattern of bytes,
1689 and can be prefixed with 0x for hex values. It may also be a string, where
1690 the string must then be wrapped with ``""``. Or it may also be a filename,
1691 where the filename must be wrapped with ``''`` in which case the file is
1692 opened and read. Note that not all the file contents will be read if that
1693 would cause the buffers to overflow. So, for example::
1695 buffer_pattern='filename'
1699 buffer_pattern="abcd"
1707 buffer_pattern=0xdeadface
1709 Also you can combine everything together in any order::
1711 buffer_pattern=0xdeadface"abcd"-12'filename'
1713 .. option:: dedupe_percentage=int
1715 If set, fio will generate this percentage of identical buffers when
1716 writing. These buffers will be naturally dedupable. The contents of the
1717 buffers depend on what other buffer compression settings have been set. It's
1718 possible to have the individual buffers either fully compressible, or not at
1719 all -- this option only controls the distribution of unique buffers. Setting
1720 this option will also enable :option:`refill_buffers` to prevent every buffer
1723 .. option:: dedupe_mode=str
1725 If ``dedupe_percentage=<int>`` is given, then this option controls how fio
1726 generates the dedupe buffers.
1729 Generate dedupe buffers by repeating previous writes
1731 Generate dedupe buffers from working set
1733 ``repeat`` is the default option for fio. Dedupe buffers are generated
1734 by repeating previous unique write.
1736 ``working_set`` is a more realistic workload.
1737 With ``working_set``, ``dedupe_working_set_percentage=<int>`` should be provided.
1738 Given that, fio will use the initial unique write buffers as its working set.
1739 Upon deciding to dedupe, fio will randomly choose a buffer from the working set.
1740 Note that by using ``working_set`` the dedupe percentage will converge
1741 to the desired over time while ``repeat`` maintains the desired percentage
1744 .. option:: dedupe_working_set_percentage=int
1746 If ``dedupe_mode=<str>`` is set to ``working_set``, then this controls
1747 the percentage of size of the file or device used as the buffers
1748 fio will choose to generate the dedupe buffers from
1750 Note that size needs to be explicitly provided and only 1 file per
1753 .. option:: dedupe_global=bool
1755 This controls whether the deduplication buffers will be shared amongst
1756 all jobs that have this option set. The buffers are spread evenly between
1759 .. option:: invalidate=bool
1761 Invalidate the buffer/page cache parts of the files to be used prior to
1762 starting I/O if the platform and file type support it. Defaults to true.
1763 This will be ignored if :option:`pre_read` is also specified for the
1766 .. option:: sync=str
1768 Whether, and what type, of synchronous I/O to use for writes. The allowed
1772 Do not use synchronous IO, the default.
1778 Use synchronous file IO. For the majority of I/O engines,
1779 this means using O_SYNC.
1785 Use synchronous data IO. For the majority of I/O engines,
1786 this means using O_DSYNC.
1789 .. option:: iomem=str, mem=str
1791 Fio can use various types of memory as the I/O unit buffer. The allowed
1795 Use memory from :manpage:`malloc(3)` as the buffers. Default memory
1799 Use shared memory as the buffers. Allocated through
1800 :manpage:`shmget(2)`.
1803 Same as shm, but use huge pages as backing.
1806 Use :manpage:`mmap(2)` to allocate buffers. May either be anonymous memory, or can
1807 be file backed if a filename is given after the option. The format
1808 is `mem=mmap:/path/to/file`.
1811 Use a memory mapped huge file as the buffer backing. Append filename
1812 after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file`.
1815 Same as mmap, but use a MMAP_SHARED mapping.
1818 Use GPU memory as the buffers for GPUDirect RDMA benchmark.
1819 The :option:`ioengine` must be `rdma`.
1821 The area allocated is a function of the maximum allowed bs size for the job,
1822 multiplied by the I/O depth given. Note that for **shmhuge** and
1823 **mmaphuge** to work, the system must have free huge pages allocated. This
1824 can normally be checked and set by reading/writing
1825 :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page
1826 is 2 or 4MiB in size depending on the platform. So to calculate the
1827 number of huge pages you need for a given job file, add up the I/O
1828 depth of all jobs (normally one unless :option:`iodepth` is used) and
1829 multiply by the maximum bs set. Then divide that number by the huge
1830 page size. You can see the size of the huge pages in
1831 :file:`/proc/meminfo`. If no huge pages are allocated by having a
1832 non-zero number in `nr_hugepages`, using **mmaphuge** or **shmhuge**
1833 will fail. Also see :option:`hugepage-size`.
1835 **mmaphuge** also needs to have hugetlbfs mounted and the file location
1836 should point there. So if it's mounted in :file:`/huge`, you would use
1837 `mem=mmaphuge:/huge/somefile`.
1839 .. option:: iomem_align=int, mem_align=int
1841 This indicates the memory alignment of the I/O memory buffers. Note that
1842 the given alignment is applied to the first I/O unit buffer, if using
1843 :option:`iodepth` the alignment of the following buffers are given by the
1844 :option:`bs` used. In other words, if using a :option:`bs` that is a
1845 multiple of the page sized in the system, all buffers will be aligned to
1846 this value. If using a :option:`bs` that is not page aligned, the alignment
1847 of subsequent I/O memory buffers is the sum of the :option:`iomem_align` and
1850 .. option:: hugepage-size=int
1852 Defines the size of a huge page. Must at least be equal to the system
1853 setting, see :file:`/proc/meminfo` and
1854 :file:`/sys/kernel/mm/hugepages/`. Defaults to 2 or 4MiB depending on
1855 the platform. Should probably always be a multiple of megabytes, so
1856 using ``hugepage-size=Xm`` is the preferred way to set this to avoid
1857 setting a non-pow-2 bad value.
1859 .. option:: lockmem=int
1861 Pin the specified amount of memory with :manpage:`mlock(2)`. Can be used to
1862 simulate a smaller amount of memory. The amount specified is per worker.
1868 .. option:: size=int
1870 The total size of file I/O for each thread of this job. Fio will run until
1871 this many bytes has been transferred, unless runtime is limited by other options
1872 (such as :option:`runtime`, for instance, or increased/decreased by :option:`io_size`).
1873 Fio will divide this size between the available files determined by options
1874 such as :option:`nrfiles`, :option:`filename`, unless :option:`filesize` is
1875 specified by the job. If the result of division happens to be 0, the size is
1876 set to the physical size of the given files or devices if they exist.
1877 If this option is not specified, fio will use the full size of the given
1878 files or devices. If the files do not exist, size must be given. It is also
1879 possible to give size as a percentage between 1 and 100. If ``size=20%`` is
1880 given, fio will use 20% of the full size of the given files or devices.
1881 In ZBD mode, value can also be set as number of zones using 'z'.
1882 Can be combined with :option:`offset` to constrain the start and end range
1883 that I/O will be done within.
1885 .. option:: io_size=int, io_limit=int
1887 Normally fio operates within the region set by :option:`size`, which means
1888 that the :option:`size` option sets both the region and size of I/O to be
1889 performed. Sometimes that is not what you want. With this option, it is
1890 possible to define just the amount of I/O that fio should do. For instance,
1891 if :option:`size` is set to 20GiB and :option:`io_size` is set to 5GiB, fio
1892 will perform I/O within the first 20GiB but exit when 5GiB have been
1893 done. The opposite is also possible -- if :option:`size` is set to 20GiB,
1894 and :option:`io_size` is set to 40GiB, then fio will do 40GiB of I/O within
1895 the 0..20GiB region.
1897 .. option:: filesize=irange(int)
1899 Individual file sizes. May be a range, in which case fio will select sizes for
1900 files at random within the given range. If not given, each created file is the
1901 same size. This option overrides :option:`size` in terms of file size, i.e. if
1902 :option:`filesize` is specified then :option:`size` becomes merely the default
1903 for :option:`io_size` and has no effect at all if :option:`io_size` is set
1906 .. option:: file_append=bool
1908 Perform I/O after the end of the file. Normally fio will operate within the
1909 size of a file. If this option is set, then fio will append to the file
1910 instead. This has identical behavior to setting :option:`offset` to the size
1911 of a file. This option is ignored on non-regular files.
1913 .. option:: fill_device=bool, fill_fs=bool
1915 Sets size to something really large and waits for ENOSPC (no space left on
1916 device) or EDQUOT (disk quota exceeded)
1917 as the terminating condition. Only makes sense with sequential
1918 write. For a read workload, the mount point will be filled first then I/O
1919 started on the result. This option doesn't make sense if operating on a raw
1920 device node, since the size of that is already known by the file system.
1921 Additionally, writing beyond end-of-device will not return ENOSPC there.
1927 .. option:: ioengine=str
1929 Defines how the job issues I/O to the file. The following types are defined:
1932 Basic :manpage:`read(2)` or :manpage:`write(2)`
1933 I/O. :manpage:`lseek(2)` is used to position the I/O location.
1934 See :option:`fsync` and :option:`fdatasync` for syncing write I/Os.
1937 Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O. Default on
1938 all supported operating systems except for Windows.
1941 Basic :manpage:`readv(2)` or :manpage:`writev(2)` I/O. Will emulate
1942 queuing by coalescing adjacent I/Os into a single submission.
1945 Basic :manpage:`preadv(2)` or :manpage:`pwritev(2)` I/O.
1948 Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O.
1951 Fast Linux native asynchronous I/O. Supports async IO
1952 for both direct and buffered IO.
1953 This engine defines engine specific options.
1956 Fast Linux native asynchronous I/O for pass through commands.
1957 This engine defines engine specific options.
1960 Linux native asynchronous I/O. Note that Linux may only support
1961 queued behavior with non-buffered I/O (set ``direct=1`` or
1963 This engine defines engine specific options.
1966 POSIX asynchronous I/O using :manpage:`aio_read(3)` and
1967 :manpage:`aio_write(3)`.
1970 Solaris native asynchronous I/O.
1973 Windows native asynchronous I/O. Default on Windows.
1976 File is memory mapped with :manpage:`mmap(2)` and data copied
1977 to/from using :manpage:`memcpy(3)`.
1980 :manpage:`splice(2)` is used to transfer the data and
1981 :manpage:`vmsplice(2)` to transfer data from user space to the
1985 SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
1986 ioctl, or if the target is an sg character device we use
1987 :manpage:`read(2)` and :manpage:`write(2)` for asynchronous
1988 I/O. Requires :option:`filename` option to specify either block or
1989 character devices. This engine supports trim operations.
1990 The sg engine includes engine specific options.
1993 Read, write, trim and ZBC/ZAC operations to a zoned
1994 block device using libzbc library. The target can be
1995 either an SG character device or a block device file.
1998 Doesn't transfer any data, just pretends to. This is mainly used to
1999 exercise fio itself and for debugging/testing purposes.
2002 Transfer over the network to given ``host:port``. Depending on the
2003 :option:`protocol` used, the :option:`hostname`, :option:`port`,
2004 :option:`listen` and :option:`filename` options are used to specify
2005 what sort of connection to make, while the :option:`protocol` option
2006 determines which protocol will be used. This engine defines engine
2010 Like **net**, but uses :manpage:`splice(2)` and
2011 :manpage:`vmsplice(2)` to map data and send/receive.
2012 This engine defines engine specific options.
2015 Doesn't transfer any data, but burns CPU cycles according to the
2016 :option:`cpuload`, :option:`cpuchunks` and :option:`cpumode` options.
2017 Setting :option:`cpuload`\=85 will cause that job to do nothing but burn 85%
2018 of the CPU. In case of SMP machines, use :option:`numjobs`\=<nr_of_cpu>
2019 to get desired CPU usage, as the cpuload only loads a
2020 single CPU at the desired rate. A job never finishes unless there is
2021 at least one non-cpuio job.
2022 Setting :option:`cpumode`\=qsort replace the default noop instructions loop
2023 by a qsort algorithm to consume more energy.
2026 The RDMA I/O engine supports both RDMA memory semantics
2027 (RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
2028 InfiniBand, RoCE and iWARP protocols. This engine defines engine
2032 I/O engine that does regular fallocate to simulate data transfer as
2036 does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
2039 does fallocate(,mode = 0).
2042 does fallocate(,mode = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
2045 I/O engine that sends :manpage:`ftruncate(2)` operations in response
2046 to write (DDIR_WRITE) events. Each ftruncate issued sets the file's
2047 size to the current block offset. :option:`blocksize` is ignored.
2050 I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
2051 defragment activity in request to DDIR_WRITE event.
2054 I/O engine supporting direct access to Ceph Reliable Autonomic
2055 Distributed Object Store (RADOS) via librados. This ioengine
2056 defines engine specific options.
2059 I/O engine supporting direct access to Ceph Rados Block Devices
2060 (RBD) via librbd without the need to use the kernel rbd driver. This
2061 ioengine defines engine specific options.
2064 I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to
2065 a WebDAV or S3 endpoint. This ioengine defines engine specific options.
2067 This engine only supports direct IO of iodepth=1; you need to scale this
2068 via numjobs. blocksize defines the size of the objects to be created.
2070 TRIM is translated to object deletion.
2073 Using GlusterFS libgfapi sync interface to direct access to
2074 GlusterFS volumes without having to go through FUSE. This ioengine
2075 defines engine specific options.
2078 Using GlusterFS libgfapi async interface to direct access to
2079 GlusterFS volumes without having to go through FUSE. This ioengine
2080 defines engine specific options.
2083 Read and write through Hadoop (HDFS). The :option:`filename` option
2084 is used to specify host,port of the hdfs name-node to connect. This
2085 engine interprets offsets a little differently. In HDFS, files once
2086 created cannot be modified so random writes are not possible. To
2087 imitate this the libhdfs engine expects a bunch of small files to be
2088 created over HDFS and will randomly pick a file from them
2089 based on the offset generated by fio backend (see the example
2090 job file to create such files, use ``rw=write`` option). Please
2091 note, it may be necessary to set environment variables to work
2092 with HDFS/libhdfs properly. Each job uses its own connection to
2096 Read, write and erase an MTD character device (e.g.,
2097 :file:`/dev/mtd0`). Discards are treated as erases. Depending on the
2098 underlying device type, the I/O may have to go in a certain pattern,
2099 e.g., on NAND, writing sequentially to erase blocks and discarding
2100 before overwriting. The `trimwrite` mode works well for this
2104 Read and write using filesystem DAX to a file on a filesystem
2105 mounted with DAX on a persistent memory device through the PMDK
2109 Read and write using device DAX to a persistent memory device (e.g.,
2110 /dev/dax0.0) through the PMDK libpmem library.
2113 Prefix to specify loading an external I/O engine object file. Append
2114 the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load
2115 ioengine :file:`foo.o` in :file:`/tmp`. The path can be either
2116 absolute or relative. See :file:`engines/skeleton_external.c` for
2117 details of writing an external I/O engine.
2120 Simply create the files and do no I/O to them. You still need to
2121 set `filesize` so that all the accounting still occurs, but no
2122 actual I/O will be done other than creating the file.
2125 Simply do stat() and do no I/O to the file. You need to set 'filesize'
2126 and 'nrfiles', so that files will be created.
2127 This engine is to measure file lookup and meta data access.
2130 Simply delete the files by unlink() and do no I/O to them. You need to set 'filesize'
2131 and 'nrfiles', so that the files will be created.
2132 This engine is to measure file delete.
2135 Read and write using mmap I/O to a file on a filesystem
2136 mounted with DAX on a persistent memory device through the PMDK
2140 Synchronous read and write using DDN's Infinite Memory Engine (IME).
2141 This engine is very basic and issues calls to IME whenever an IO is
2145 Synchronous read and write using DDN's Infinite Memory Engine (IME).
2146 This engine uses iovecs and will try to stack as much IOs as possible
2147 (if the IOs are "contiguous" and the IO depth is not exceeded)
2148 before issuing a call to IME.
2151 Asynchronous read and write using DDN's Infinite Memory Engine (IME).
2152 This engine will try to stack as much IOs as possible by creating
2153 requests for IME. FIO will then decide when to commit these requests.
2156 Read and write iscsi lun with libiscsi.
2159 Read and write a Network Block Device (NBD).
2162 I/O engine supporting libcufile synchronous access to nvidia-fs and a
2163 GPUDirect Storage-supported filesystem. This engine performs
2164 I/O without transferring buffers between user-space and the kernel,
2165 unless :option:`verify` is set or :option:`cuda_io` is `posix`.
2166 :option:`iomem` must not be `cudamalloc`. This ioengine defines
2167 engine specific options.
2170 I/O engine supporting asynchronous read and write operations to the
2171 DAOS File System (DFS) via libdfs.
2174 I/O engine supporting asynchronous read and write operations to
2175 NFS filesystems from userspace via libnfs. This is useful for
2176 achieving higher concurrency and thus throughput than is possible
2180 Execute 3rd party tools. Could be used to perform monitoring during jobs runtime.
2183 I/O engine using the xNVMe C API, for NVMe devices. The xnvme engine provides
2184 flexibility to access GNU/Linux Kernel NVMe driver via libaio, IOCTLs, io_uring,
2185 the SPDK NVMe driver, or your own custom NVMe driver. The xnvme engine includes
2186 engine specific options. (See https://xnvme.io).
2188 I/O engine specific parameters
2189 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2191 In addition, there are some parameters which are only valid when a specific
2192 :option:`ioengine` is in use. These are used identically to normal parameters,
2193 with the caveat that when used on the command line, they must come after the
2194 :option:`ioengine` that defines them is selected.
2196 .. option:: cmdprio_percentage=int[,int] : [io_uring] [libaio]
2198 Set the percentage of I/O that will be issued with the highest priority.
2199 Default: 0. A single value applies to reads and writes. Comma-separated
2200 values may be specified for reads and writes. For this option to be
2201 effective, NCQ priority must be supported and enabled, and the :option:`direct`
2202 option must be set. fio must also be run as the root user. Unlike
2203 slat/clat/lat stats, which can be tracked and reported independently, per
2204 priority stats only track and report a single type of latency. By default,
2205 completion latency (clat) will be reported, if :option:`lat_percentiles` is
2206 set, total latency (lat) will be reported.
2208 .. option:: cmdprio_class=int[,int] : [io_uring] [libaio]
2210 Set the I/O priority class to use for I/Os that must be issued with
2211 a priority when :option:`cmdprio_percentage` or
2212 :option:`cmdprio_bssplit` is set. If not specified when
2213 :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
2214 this defaults to the highest priority class. A single value applies
2215 to reads and writes. Comma-separated values may be specified for
2216 reads and writes. See :manpage:`ionice(1)`. See also the
2217 :option:`prioclass` option.
2219 .. option:: cmdprio=int[,int] : [io_uring] [libaio]
2221 Set the I/O priority value to use for I/Os that must be issued with
2222 a priority when :option:`cmdprio_percentage` or
2223 :option:`cmdprio_bssplit` is set. If not specified when
2224 :option:`cmdprio_percentage` or :option:`cmdprio_bssplit` is set,
2226 Linux limits us to a positive value between 0 and 7, with 0 being the
2227 highest. A single value applies to reads and writes. Comma-separated
2228 values may be specified for reads and writes. See :manpage:`ionice(1)`.
2229 Refer to an appropriate manpage for other operating systems since
2230 meaning of priority may differ. See also the :option:`prio` option.
2232 .. option:: cmdprio_bssplit=str[,str] : [io_uring] [libaio]
2234 To get a finer control over I/O priority, this option allows
2235 specifying the percentage of IOs that must have a priority set
2236 depending on the block size of the IO. This option is useful only
2237 when used together with the :option:`bssplit` option, that is,
2238 multiple different block sizes are used for reads and writes.
2240 The first accepted format for this option is the same as the format of
2241 the :option:`bssplit` option:
2243 cmdprio_bssplit=blocksize/percentage:blocksize/percentage
2245 In this case, each entry will use the priority class and priority
2246 level defined by the options :option:`cmdprio_class` and
2247 :option:`cmdprio` respectively.
2249 The second accepted format for this option is:
2251 cmdprio_bssplit=blocksize/percentage/class/level:blocksize/percentage/class/level
2253 In this case, the priority class and priority level is defined inside
2254 each entry. In comparison with the first accepted format, the second
2255 accepted format does not restrict all entries to have the same priority
2256 class and priority level.
2258 For both formats, only the read and write data directions are supported,
2259 values for trim IOs are ignored. This option is mutually exclusive with
2260 the :option:`cmdprio_percentage` option.
2262 .. option:: fixedbufs : [io_uring] [io_uring_cmd]
2264 If fio is asked to do direct IO, then Linux will map pages for each
2265 IO call, and release them when IO is done. If this option is set, the
2266 pages are pre-mapped before IO is started. This eliminates the need to
2267 map and release for each IO. This is more efficient, and reduces the
2270 .. option:: nonvectored : [io_uring] [io_uring_cmd]
2272 With this option, fio will use non-vectored read/write commands, where
2273 address must contain the address directly. Default is -1.
2275 .. option:: force_async=int : [io_uring] [io_uring_cmd]
2277 Normal operation for io_uring is to try and issue an sqe as
2278 non-blocking first, and if that fails, execute it in an async manner.
2279 With this option set to N, then every N request fio will ask sqe to
2280 be issued in an async manner. Default is 0.
2282 .. option:: registerfiles : [io_uring] [io_uring_cmd]
2284 With this option, fio registers the set of files being used with the
2285 kernel. This avoids the overhead of managing file counts in the kernel,
2286 making the submission and completion part more lightweight. Required
2287 for the below :option:`sqthread_poll` option.
2289 .. option:: sqthread_poll : [io_uring] [io_uring_cmd] [xnvme]
2291 Normally fio will submit IO by issuing a system call to notify the
2292 kernel of available items in the SQ ring. If this option is set, the
2293 act of submitting IO will be done by a polling thread in the kernel.
2294 This frees up cycles for fio, at the cost of using more CPU in the
2297 .. option:: sqthread_poll_cpu : [io_uring] [io_uring_cmd]
2299 When :option:`sqthread_poll` is set, this option provides a way to
2300 define which CPU should be used for the polling thread.
2302 .. option:: cmd_type=str : [io_uring_cmd]
2304 Specifies the type of uring passthrough command to be used. Supported
2305 value is nvme. Default is nvme.
2309 [io_uring] [io_uring_cmd] [xnvme]
2311 If this option is set, fio will attempt to use polled IO completions.
2312 Normal IO completions generate interrupts to signal the completion of
2313 IO, polled completions do not. Hence they are require active reaping
2314 by the application. The benefits are more efficient IO for high IOPS
2315 scenarios, and lower latencies for low queue depth IO.
2319 Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority
2324 If this option is set, fio will attempt to use polled IO completions.
2325 This will have a similar effect as (io_uring)hipri. Only SCSI READ and
2326 WRITE commands will have the SGV4_FLAG_HIPRI set (not UNMAP (trim) nor
2327 VERIFY). Older versions of the Linux sg driver that do not support
2328 hipri will simply ignore this flag and do normal IO. The Linux SCSI
2329 Low Level Driver (LLD) that "owns" the device also needs to support
2330 hipri (also known as iopoll and mq_poll). The MegaRAID driver is an
2331 example of a SCSI LLD. Default: clear (0) which does normal
2332 (interrupted based) IO.
2334 .. option:: userspace_reap : [libaio]
2336 Normally, with the libaio engine in use, fio will use the
2337 :manpage:`io_getevents(2)` system call to reap newly returned events. With
2338 this flag turned on, the AIO ring will be read directly from user-space to
2339 reap events. The reaping mode is only enabled when polling for a minimum of
2340 0 events (e.g. when :option:`iodepth_batch_complete` `=0`).
2342 .. option:: hipri_percentage : [pvsync2]
2344 When hipri is set this determines the probability of a pvsync2 I/O being high
2345 priority. The default is 100%.
2347 .. option:: nowait : [pvsync2] [libaio] [io_uring]
2349 By default if a request cannot be executed immediately (e.g. resource starvation,
2350 waiting on locks) it is queued and the initiating process will be blocked until
2351 the required resource becomes free.
2353 This option sets the RWF_NOWAIT flag (supported from the 4.14 Linux kernel) and
2354 the call will return instantly with EAGAIN or a partial result rather than waiting.
2356 It is useful to also use ignore_error=EAGAIN when using this option.
2358 Note: glibc 2.27, 2.28 have a bug in syscall wrappers preadv2, pwritev2.
2359 They return EOPNOTSUP instead of EAGAIN.
2361 For cached I/O, using this option usually means a request operates only with
2362 cached data. Currently the RWF_NOWAIT flag does not supported for cached write.
2364 For direct I/O, requests will only succeed if cache invalidation isn't required,
2365 file blocks are fully allocated and the disk request could be issued immediately.
2367 .. option:: cpuload=int : [cpuio]
2369 Attempt to use the specified percentage of CPU cycles. This is a mandatory
2370 option when using cpuio I/O engine.
2372 .. option:: cpuchunks=int : [cpuio]
2374 Split the load into cycles of the given time. In microseconds.
2376 .. option:: cpumode=str : [cpuio]
2378 Specify how to stress the CPU. It can take these two values:
2381 This is the default where the CPU executes noop instructions.
2383 Replace the default noop instructions loop with a qsort algorithm to
2384 consume more energy.
2386 .. option:: exit_on_io_done=bool : [cpuio]
2388 Detect when I/O threads are done, then exit.
2390 .. option:: namenode=str : [libhdfs]
2392 The hostname or IP address of a HDFS cluster namenode to contact.
2394 .. option:: port=int
2398 The listening port of the HFDS cluster namenode.
2402 The TCP or UDP port to bind to or connect to. If this is used with
2403 :option:`numjobs` to spawn multiple instances of the same job type, then
2404 this will be the starting port number since fio will use a range of
2409 The port to use for RDMA-CM communication. This should be the same value
2410 on the client and the server side.
2412 .. option:: hostname=str : [netsplice] [net] [rdma]
2414 The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If the job
2415 is a TCP listener or UDP reader, the hostname is not used and must be omitted
2416 unless it is a valid UDP multicast address.
2418 .. option:: serverip=str : [librpma_*]
2420 The IP address to be used for RDMA-CM based I/O.
2422 .. option:: direct_write_to_pmem=bool : [librpma_*]
2424 Set to 1 only when Direct Write to PMem from the remote host is possible.
2425 Otherwise, set to 0.
2427 .. option:: busy_wait_polling=bool : [librpma_*_server]
2429 Set to 0 to wait for completion instead of busy-wait polling completion.
2432 .. option:: interface=str : [netsplice] [net]
2434 The IP address of the network interface used to send or receive UDP
2437 .. option:: ttl=int : [netsplice] [net]
2439 Time-to-live value for outgoing UDP multicast packets. Default: 1.
2441 .. option:: nodelay=bool : [netsplice] [net]
2443 Set TCP_NODELAY on TCP connections.
2445 .. option:: protocol=str, proto=str : [netsplice] [net]
2447 The network protocol to use. Accepted values are:
2450 Transmission control protocol.
2452 Transmission control protocol V6.
2454 User datagram protocol.
2456 User datagram protocol V6.
2460 When the protocol is TCP or UDP, the port must also be given, as well as the
2461 hostname if the job is a TCP listener or UDP reader. For unix sockets, the
2462 normal :option:`filename` option should be used and the port is invalid.
2464 .. option:: listen : [netsplice] [net]
2466 For TCP network connections, tell fio to listen for incoming connections
2467 rather than initiating an outgoing connection. The :option:`hostname` must
2468 be omitted if this option is used.
2470 .. option:: pingpong : [netsplice] [net]
2472 Normally a network writer will just continue writing data, and a network
2473 reader will just consume packages. If ``pingpong=1`` is set, a writer will
2474 send its normal payload to the reader, then wait for the reader to send the
2475 same payload back. This allows fio to measure network latencies. The
2476 submission and completion latencies then measure local time spent sending or
2477 receiving, and the completion latency measures how long it took for the
2478 other end to receive and send back. For UDP multicast traffic
2479 ``pingpong=1`` should only be set for a single reader when multiple readers
2480 are listening to the same address.
2482 .. option:: window_size : [netsplice] [net]
2484 Set the desired socket buffer size for the connection.
2486 .. option:: mss : [netsplice] [net]
2488 Set the TCP maximum segment size (TCP_MAXSEG).
2490 .. option:: donorname=str : [e4defrag]
2492 File will be used as a block donor (swap extents between files).
2494 .. option:: inplace=int : [e4defrag]
2496 Configure donor file blocks allocation strategy:
2499 Default. Preallocate donor's file on init.
2501 Allocate space immediately inside defragment event, and free right
2504 .. option:: clustername=str : [rbd,rados]
2506 Specifies the name of the Ceph cluster.
2508 .. option:: rbdname=str : [rbd]
2510 Specifies the name of the RBD.
2512 .. option:: clientname=str : [rbd,rados]
2514 Specifies the username (without the 'client.' prefix) used to access the
2515 Ceph cluster. If the *clustername* is specified, the *clientname* shall be
2516 the full *type.id* string. If no type. prefix is given, fio will add
2517 'client.' by default.
2519 .. option:: conf=str : [rados]
2521 Specifies the configuration path of ceph cluster, so conf file does not
2522 have to be /etc/ceph/ceph.conf.
2524 .. option:: busy_poll=bool : [rbd,rados]
2526 Poll store instead of waiting for completion. Usually this provides better
2527 throughput at cost of higher(up to 100%) CPU utilization.
2529 .. option:: touch_objects=bool : [rados]
2531 During initialization, touch (create if do not exist) all objects (files).
2532 Touching all objects affects ceph caches and likely impacts test results.
2535 .. option:: pool=str :
2539 Specifies the name of the Ceph pool containing RBD or RADOS data.
2543 Specify the label or UUID of the DAOS pool to connect to.
2545 .. option:: cont=str : [dfs]
2547 Specify the label or UUID of the DAOS container to open.
2549 .. option:: chunk_size=int
2553 Specificy a different chunk size (in bytes) for the dfs file.
2554 Use DAOS container's chunk size by default.
2558 The size of the chunk to use for each file.
2560 .. option:: object_class=str : [dfs]
2562 Specificy a different object class for the dfs file.
2563 Use DAOS container's object class by default.
2565 .. option:: skip_bad=bool : [mtd]
2567 Skip operations against known bad blocks.
2569 .. option:: hdfsdirectory : [libhdfs]
2571 libhdfs will create chunk in this HDFS directory.
2573 .. option:: verb=str : [rdma]
2575 The RDMA verb to use on this side of the RDMA ioengine connection. Valid
2576 values are write, read, send and recv. These correspond to the equivalent
2577 RDMA verbs (e.g. write = rdma_write etc.). Note that this only needs to be
2578 specified on the client side of the connection. See the examples folder.
2580 .. option:: bindname=str : [rdma]
2582 The name to use to bind the local RDMA-CM connection to a local RDMA device.
2583 This could be a hostname or an IPv4 or IPv6 address. On the server side this
2584 will be passed into the rdma_bind_addr() function and on the client site it
2585 will be used in the rdma_resolve_add() function. This can be useful when
2586 multiple paths exist between the client and the server or in certain loopback
2589 .. option:: stat_type=str : [filestat]
2591 Specify stat system call type to measure lookup/getattr performance.
2592 Default is **stat** for :manpage:`stat(2)`.
2594 .. option:: readfua=bool : [sg]
2596 With readfua option set to 1, read operations include
2597 the force unit access (fua) flag. Default is 0.
2599 .. option:: writefua=bool : [sg]
2601 With writefua option set to 1, write operations include
2602 the force unit access (fua) flag. Default is 0.
2604 .. option:: sg_write_mode=str : [sg]
2606 Specify the type of write commands to issue. This option can take three values:
2609 This is the default where write opcodes are issued as usual.
2610 **write_and_verify**
2611 Issue WRITE AND VERIFY commands. The BYTCHK bit is set to 0. This
2612 directs the device to carry out a medium verification with no data
2613 comparison. The writefua option is ignored with this selection.
2615 This option is deprecated. Use write_and_verify instead.
2617 Issue WRITE SAME commands. This transfers a single block to the device
2618 and writes this same block of data to a contiguous sequence of LBAs
2619 beginning at the specified offset. fio's block size parameter specifies
2620 the amount of data written with each command. However, the amount of data
2621 actually transferred to the device is equal to the device's block
2622 (sector) size. For a device with 512 byte sectors, blocksize=8k will
2623 write 16 sectors with each command. fio will still generate 8k of data
2624 for each command but only the first 512 bytes will be used and
2625 transferred to the device. The writefua option is ignored with this
2628 This option is deprecated. Use write_same instead.
2630 Issue WRITE SAME(16) commands as above but with the No Data Output
2631 Buffer (NDOB) bit set. No data will be transferred to the device with
2632 this bit set. Data written will be a pre-determined pattern such as
2635 Issue WRITE STREAM(16) commands. Use the **stream_id** option to specify
2636 the stream identifier.
2637 **verify_bytchk_00**
2638 Issue VERIFY commands with BYTCHK set to 00. This directs the
2639 device to carry out a medium verification with no data comparison.
2640 **verify_bytchk_01**
2641 Issue VERIFY commands with BYTCHK set to 01. This directs the device to
2642 compare the data on the device with the data transferred to the device.
2643 **verify_bytchk_11**
2644 Issue VERIFY commands with BYTCHK set to 11. This transfers a
2645 single block to the device and compares the contents of this block with the
2646 data on the device beginning at the specified offset. fio's block size
2647 parameter specifies the total amount of data compared with this command.
2648 However, only one block (sector) worth of data is transferred to the device.
2649 This is similar to the WRITE SAME command except that data is compared instead
2652 .. option:: stream_id=int : [sg]
2654 Set the stream identifier for WRITE STREAM commands. If this is set to 0 (which is not
2655 a valid stream identifier) fio will open a stream and then close it when done. Default
2658 .. option:: http_host=str : [http]
2660 Hostname to connect to. For S3, this could be the bucket hostname.
2661 Default is **localhost**
2663 .. option:: http_user=str : [http]
2665 Username for HTTP authentication.
2667 .. option:: http_pass=str : [http]
2669 Password for HTTP authentication.
2671 .. option:: https=str : [http]
2673 Enable HTTPS instead of http. *on* enables HTTPS; *insecure*
2674 will enable HTTPS, but disable SSL peer verification (use with
2675 caution!). Default is **off**
2677 .. option:: http_mode=str : [http]
2679 Which HTTP access mode to use: *webdav*, *swift*, or *s3*.
2680 Default is **webdav**
2682 .. option:: http_s3_region=str : [http]
2684 The S3 region/zone string.
2685 Default is **us-east-1**
2687 .. option:: http_s3_key=str : [http]
2691 .. option:: http_s3_keyid=str : [http]
2693 The S3 key/access id.
2695 .. option:: http_swift_auth_token=str : [http]
2697 The Swift auth token. See the example configuration file on how
2700 .. option:: http_verbose=int : [http]
2702 Enable verbose requests from libcurl. Useful for debugging. 1
2703 turns on verbose logging from libcurl, 2 additionally enables
2704 HTTP IO tracing. Default is **0**
2706 .. option:: uri=str : [nbd]
2708 Specify the NBD URI of the server to test. The string
2709 is a standard NBD URI
2710 (see https://github.com/NetworkBlockDevice/nbd/tree/master/doc).
2711 Example URIs: nbd://localhost:10809
2712 nbd+unix:///?socket=/tmp/socket
2713 nbds://tlshost/exportname
2715 .. option:: gpu_dev_ids=str : [libcufile]
2717 Specify the GPU IDs to use with CUDA. This is a colon-separated list of
2718 int. GPUs are assigned to workers roundrobin. Default is 0.
2720 .. option:: cuda_io=str : [libcufile]
2722 Specify the type of I/O to use with CUDA. Default is **cufile**.
2725 Use libcufile and nvidia-fs. This option performs I/O directly
2726 between a GPUDirect Storage filesystem and GPU buffers,
2727 avoiding use of a bounce buffer. If :option:`verify` is set,
2728 cudaMemcpy is used to copy verificaton data between RAM and GPU.
2729 Verification data is copied from RAM to GPU before a write
2730 and from GPU to RAM after a read. :option:`direct` must be 1.
2732 Use POSIX to perform I/O with a RAM buffer, and use cudaMemcpy
2733 to transfer data between RAM and the GPUs. Data is copied from
2734 GPU to RAM before a write and copied from RAM to GPU after a
2735 read. :option:`verify` does not affect use of cudaMemcpy.
2737 .. option:: nfs_url=str : [nfs]
2739 URL in libnfs format, eg nfs://<server|ipv4|ipv6>/path[?arg=val[&arg=val]*]
2740 Refer to the libnfs README for more details.
2742 .. option:: program=str : [exec]
2744 Specify the program to execute.
2746 .. option:: arguments=str : [exec]
2748 Specify arguments to pass to program.
2749 Some special variables can be expanded to pass fio's job details to the program.
2752 Replaced by the duration of the job in seconds.
2754 Replaced by the name of the job.
2756 .. option:: grace_time=int : [exec]
2758 Specify the time between the SIGTERM and SIGKILL signals. Default is 1 second.
2760 .. option:: std_redirect=bool : [exec]
2762 If set, stdout and stderr streams are redirected to files named from the job name. Default is true.
2764 .. option:: xnvme_async=str : [xnvme]
2766 Select the xnvme async command interface. This can take these values.
2769 This is default and used to emulate asynchronous I/O.
2771 Use thread pool for Asynchronous I/O.
2773 Use Linux io_uring/liburing for Asynchronous I/O.
2775 Use Linux aio for Asynchronous I/O.
2777 Use POSIX aio for Asynchronous I/O.
2779 Use nil-io; For introspective perf. evaluation
2781 .. option:: xnvme_sync=str : [xnvme]
2783 Select the xnvme synchronous command interface. This can take these values.
2786 This is default and uses Linux NVMe Driver ioctl() for synchronous I/O.
2788 Use pread()/write() for synchronous I/O.
2790 .. option:: xnvme_admin=str : [xnvme]
2792 Select the xnvme admin command interface. This can take these values.
2795 This is default and uses linux NVMe Driver ioctl() for admin commands.
2797 Use Linux Block Layer ioctl() and sysfs for admin commands.
2799 Use file-stat to construct NVMe idfy responses.
2801 .. option:: xnvme_dev_nsid=int : [xnvme]
2803 xnvme namespace identifier, for userspace NVMe driver.
2805 .. option:: xnvme_iovec=int : [xnvme]
2807 If this option is set. xnvme will use vectored read/write commands.
2812 .. option:: iodepth=int
2814 Number of I/O units to keep in flight against the file. Note that
2815 increasing *iodepth* beyond 1 will not affect synchronous ioengines (except
2816 for small degrees when :option:`verify_async` is in use). Even async
2817 engines may impose OS restrictions causing the desired depth not to be
2818 achieved. This may happen on Linux when using libaio and not setting
2819 :option:`direct`\=1, since buffered I/O is not async on that OS. Keep an
2820 eye on the I/O depth distribution in the fio output to verify that the
2821 achieved depth is as expected. Default: 1.
2823 .. option:: iodepth_batch_submit=int, iodepth_batch=int
2825 This defines how many pieces of I/O to submit at once. It defaults to 1
2826 which means that we submit each I/O as soon as it is available, but can be
2827 raised to submit bigger batches of I/O at the time. If it is set to 0 the
2828 :option:`iodepth` value will be used.
2830 .. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int
2832 This defines how many pieces of I/O to retrieve at once. It defaults to 1
2833 which means that we'll ask for a minimum of 1 I/O in the retrieval process
2834 from the kernel. The I/O retrieval will go on until we hit the limit set by
2835 :option:`iodepth_low`. If this variable is set to 0, then fio will always
2836 check for completed events before queuing more I/O. This helps reduce I/O
2837 latency, at the cost of more retrieval system calls.
2839 .. option:: iodepth_batch_complete_max=int
2841 This defines maximum pieces of I/O to retrieve at once. This variable should
2842 be used along with :option:`iodepth_batch_complete_min`\=int variable,
2843 specifying the range of min and max amount of I/O which should be
2844 retrieved. By default it is equal to the :option:`iodepth_batch_complete_min`
2849 iodepth_batch_complete_min=1
2850 iodepth_batch_complete_max=<iodepth>
2852 which means that we will retrieve at least 1 I/O and up to the whole
2853 submitted queue depth. If none of I/O has been completed yet, we will wait.
2857 iodepth_batch_complete_min=0
2858 iodepth_batch_complete_max=<iodepth>
2860 which means that we can retrieve up to the whole submitted queue depth, but
2861 if none of I/O has been completed yet, we will NOT wait and immediately exit
2862 the system call. In this example we simply do polling.
2864 .. option:: iodepth_low=int
2866 The low water mark indicating when to start filling the queue
2867 again. Defaults to the same as :option:`iodepth`, meaning that fio will
2868 attempt to keep the queue full at all times. If :option:`iodepth` is set to
2869 e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of
2870 16 requests, it will let the depth drain down to 4 before starting to fill
2873 .. option:: serialize_overlap=bool
2875 Serialize in-flight I/Os that might otherwise cause or suffer from data races.
2876 When two or more I/Os are submitted simultaneously, there is no guarantee that
2877 the I/Os will be processed or completed in the submitted order. Further, if
2878 two or more of those I/Os are writes, any overlapping region between them can
2879 become indeterminate/undefined on certain storage. These issues can cause
2880 verification to fail erratically when at least one of the racing I/Os is
2881 changing data and the overlapping region has a non-zero size. Setting
2882 ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
2883 serializing in-flight I/Os that have a non-zero overlap. Note that setting
2884 this option can reduce both performance and the :option:`iodepth` achieved.
2886 This option only applies to I/Os issued for a single job except when it is
2887 enabled along with :option:`io_submit_mode`\=offload. In offload mode, fio
2888 will check for overlap among all I/Os submitted by offload jobs with :option:`serialize_overlap`
2893 .. option:: io_submit_mode=str
2895 This option controls how fio submits the I/O to the I/O engine. The default
2896 is `inline`, which means that the fio job threads submit and reap I/O
2897 directly. If set to `offload`, the job threads will offload I/O submission
2898 to a dedicated pool of I/O threads. This requires some coordination and thus
2899 has a bit of extra overhead, especially for lower queue depth I/O where it
2900 can increase latencies. The benefit is that fio can manage submission rates
2901 independently of the device completion rates. This avoids skewed latency
2902 reporting if I/O gets backed up on the device side (the coordinated omission
2903 problem). Note that this option cannot reliably be used with async IO
2910 .. option:: thinktime=time
2912 Stall the job for the specified period of time after an I/O has completed before issuing the
2913 next. May be used to simulate processing being done by an application.
2914 When the unit is omitted, the value is interpreted in microseconds. See
2915 :option:`thinktime_blocks`, :option:`thinktime_iotime` and :option:`thinktime_spin`.
2917 .. option:: thinktime_spin=time
2919 Only valid if :option:`thinktime` is set - pretend to spend CPU time doing
2920 something with the data received, before falling back to sleeping for the
2921 rest of the period specified by :option:`thinktime`. When the unit is
2922 omitted, the value is interpreted in microseconds.
2924 .. option:: thinktime_blocks=int
2926 Only valid if :option:`thinktime` is set - control how many blocks to issue,
2927 before waiting :option:`thinktime` usecs. If not set, defaults to 1 which will make
2928 fio wait :option:`thinktime` usecs after every block. This effectively makes any
2929 queue depth setting redundant, since no more than 1 I/O will be queued
2930 before we have to complete it and do our :option:`thinktime`. In other words, this
2931 setting effectively caps the queue depth if the latter is larger.
2933 .. option:: thinktime_blocks_type=str
2935 Only valid if :option:`thinktime` is set - control how :option:`thinktime_blocks`
2936 triggers. The default is `complete`, which triggers thinktime when fio completes
2937 :option:`thinktime_blocks` blocks. If this is set to `issue`, then the trigger happens
2940 .. option:: thinktime_iotime=time
2942 Only valid if :option:`thinktime` is set - control :option:`thinktime`
2943 interval by time. The :option:`thinktime` stall is repeated after IOs
2944 are executed for :option:`thinktime_iotime`. For example,
2945 ``--thinktime_iotime=9s --thinktime=1s`` repeat 10-second cycle with IOs
2946 for 9 seconds and stall for 1 second. When the unit is omitted,
2947 :option:`thinktime_iotime` is interpreted as a number of seconds. If
2948 this option is used together with :option:`thinktime_blocks`, the
2949 :option:`thinktime` stall is repeated after :option:`thinktime_iotime`
2950 or after :option:`thinktime_blocks` IOs, whichever happens first.
2952 .. option:: rate=int[,int][,int]
2954 Cap the bandwidth used by this job. The number is in bytes/sec, the normal
2955 suffix rules apply. Comma-separated values may be specified for reads,
2956 writes, and trims as described in :option:`blocksize`.
2958 For example, using `rate=1m,500k` would limit reads to 1MiB/sec and writes to
2959 500KiB/sec. Capping only reads or writes can be done with `rate=,500k` or
2960 `rate=500k,` where the former will only limit writes (to 500KiB/sec) and the
2961 latter will only limit reads.
2963 .. option:: rate_min=int[,int][,int]
2965 Tell fio to do whatever it can to maintain at least this bandwidth. Failing
2966 to meet this requirement will cause the job to exit. Comma-separated values
2967 may be specified for reads, writes, and trims as described in
2968 :option:`blocksize`.
2970 .. option:: rate_iops=int[,int][,int]
2972 Cap the bandwidth to this number of IOPS. Basically the same as
2973 :option:`rate`, just specified independently of bandwidth. If the job is
2974 given a block size range instead of a fixed value, the smallest block size
2975 is used as the metric. Comma-separated values may be specified for reads,
2976 writes, and trims as described in :option:`blocksize`.
2978 .. option:: rate_iops_min=int[,int][,int]
2980 If fio doesn't meet this rate of I/O, it will cause the job to exit.
2981 Comma-separated values may be specified for reads, writes, and trims as
2982 described in :option:`blocksize`.
2984 .. option:: rate_process=str
2986 This option controls how fio manages rated I/O submissions. The default is
2987 `linear`, which submits I/O in a linear fashion with fixed delays between
2988 I/Os that gets adjusted based on I/O completion rates. If this is set to
2989 `poisson`, fio will submit I/O based on a more real world random request
2990 flow, known as the Poisson process
2991 (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be
2992 10^6 / IOPS for the given workload.
2994 .. option:: rate_ignore_thinktime=bool
2996 By default, fio will attempt to catch up to the specified rate setting,
2997 if any kind of thinktime setting was used. If this option is set, then
2998 fio will ignore the thinktime and continue doing IO at the specified
2999 rate, instead of entering a catch-up mode after thinktime is done.
3005 .. option:: latency_target=time
3007 If set, fio will attempt to find the max performance point that the given
3008 workload will run at while maintaining a latency below this target. When
3009 the unit is omitted, the value is interpreted in microseconds. See
3010 :option:`latency_window` and :option:`latency_percentile`.
3012 .. option:: latency_window=time
3014 Used with :option:`latency_target` to specify the sample window that the job
3015 is run at varying queue depths to test the performance. When the unit is
3016 omitted, the value is interpreted in microseconds.
3018 .. option:: latency_percentile=float
3020 The percentage of I/Os that must fall within the criteria specified by
3021 :option:`latency_target` and :option:`latency_window`. If not set, this
3022 defaults to 100.0, meaning that all I/Os must be equal or below to the value
3023 set by :option:`latency_target`.
3025 .. option:: latency_run=bool
3027 Used with :option:`latency_target`. If false (default), fio will find
3028 the highest queue depth that meets :option:`latency_target` and exit. If
3029 true, fio will continue running and try to meet :option:`latency_target`
3030 by adjusting queue depth.
3032 .. option:: max_latency=time[,time][,time]
3034 If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
3035 maximum latency. When the unit is omitted, the value is interpreted in
3036 microseconds. Comma-separated values may be specified for reads, writes,
3037 and trims as described in :option:`blocksize`.
3039 .. option:: rate_cycle=int
3041 Average bandwidth for :option:`rate` and :option:`rate_min` over this number
3042 of milliseconds. Defaults to 1000.
3048 .. option:: write_iolog=str
3050 Write the issued I/O patterns to the specified file. See
3051 :option:`read_iolog`. Specify a separate file for each job, otherwise the
3052 iologs will be interspersed and the file may be corrupt. This file will
3053 be opened in append mode.
3055 .. option:: read_iolog=str
3057 Open an iolog with the specified filename and replay the I/O patterns it
3058 contains. This can be used to store a workload and replay it sometime
3059 later. The iolog given may also be a blktrace binary file, which allows fio
3060 to replay a workload captured by :command:`blktrace`. See
3061 :manpage:`blktrace(8)` for how to capture such logging data. For blktrace
3062 replay, the file needs to be turned into a blkparse binary data file first
3063 (``blkparse <device> -o /dev/null -d file_for_fio.bin``).
3064 You can specify a number of files by separating the names with a ':'
3065 character. See the :option:`filename` option for information on how to
3066 escape ':' characters within the file names. These files will
3067 be sequentially assigned to job clones created by :option:`numjobs`.
3068 '-' is a reserved name, meaning read from stdin, notably if
3069 :option:`filename` is set to '-' which means stdin as well, then
3070 this flag can't be set to '-'.
3072 .. option:: read_iolog_chunked=bool
3074 Determines how iolog is read. If false(default) entire :option:`read_iolog`
3075 will be read at once. If selected true, input from iolog will be read
3076 gradually. Useful when iolog is very large, or it is generated.
3078 .. option:: merge_blktrace_file=str
3080 When specified, rather than replaying the logs passed to :option:`read_iolog`,
3081 the logs go through a merge phase which aggregates them into a single
3082 blktrace. The resulting file is then passed on as the :option:`read_iolog`
3083 parameter. The intention here is to make the order of events consistent.
3084 This limits the influence of the scheduler compared to replaying multiple
3085 blktraces via concurrent jobs.
3087 .. option:: merge_blktrace_scalars=float_list
3089 This is a percentage based option that is index paired with the list of
3090 files passed to :option:`read_iolog`. When merging is performed, scale
3091 the time of each event by the corresponding amount. For example,
3092 ``--merge_blktrace_scalars="50:100"`` runs the first trace in halftime
3093 and the second trace in realtime. This knob is separately tunable from
3094 :option:`replay_time_scale` which scales the trace during runtime and
3095 does not change the output of the merge unlike this option.
3097 .. option:: merge_blktrace_iters=float_list
3099 This is a whole number option that is index paired with the list of files
3100 passed to :option:`read_iolog`. When merging is performed, run each trace
3101 for the specified number of iterations. For example,
3102 ``--merge_blktrace_iters="2:1"`` runs the first trace for two iterations
3103 and the second trace for one iteration.
3105 .. option:: replay_no_stall=bool
3107 When replaying I/O with :option:`read_iolog` the default behavior is to
3108 attempt to respect the timestamps within the log and replay them with the
3109 appropriate delay between IOPS. By setting this variable fio will not
3110 respect the timestamps and attempt to replay them as fast as possible while
3111 still respecting ordering. The result is the same I/O pattern to a given
3112 device, but different timings.
3114 .. option:: replay_time_scale=int
3116 When replaying I/O with :option:`read_iolog`, fio will honor the
3117 original timing in the trace. With this option, it's possible to scale
3118 the time. It's a percentage option, if set to 50 it means run at 50%
3119 the original IO rate in the trace. If set to 200, run at twice the
3120 original IO rate. Defaults to 100.
3122 .. option:: replay_redirect=str
3124 While replaying I/O patterns using :option:`read_iolog` the default behavior
3125 is to replay the IOPS onto the major/minor device that each IOP was recorded
3126 from. This is sometimes undesirable because on a different machine those
3127 major/minor numbers can map to a different device. Changing hardware on the
3128 same system can also result in a different major/minor mapping.
3129 ``replay_redirect`` causes all I/Os to be replayed onto the single specified
3130 device regardless of the device it was recorded
3131 from. i.e. :option:`replay_redirect`\= :file:`/dev/sdc` would cause all I/O
3132 in the blktrace or iolog to be replayed onto :file:`/dev/sdc`. This means
3133 multiple devices will be replayed onto a single device, if the trace
3134 contains multiple devices. If you want multiple devices to be replayed
3135 concurrently to multiple redirected devices you must blkparse your trace
3136 into separate traces and replay them with independent fio invocations.
3137 Unfortunately this also breaks the strict time ordering between multiple
3140 .. option:: replay_align=int
3142 Force alignment of the byte offsets in a trace to this value. The value
3143 must be a power of 2.
3145 .. option:: replay_scale=int
3147 Scale byte offsets down by this factor when replaying traces. Should most
3148 likely use :option:`replay_align` as well.
3150 .. option:: replay_skip=str
3152 Sometimes it's useful to skip certain IO types in a replay trace.
3153 This could be, for instance, eliminating the writes in the trace.
3154 Or not replaying the trims/discards, if you are redirecting to
3155 a device that doesn't support them. This option takes a comma
3156 separated list of read, write, trim, sync.
3159 Threads, processes and job synchronization
3160 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3164 Fio defaults to creating jobs by using fork, however if this option is
3165 given, fio will create jobs by using POSIX Threads' function
3166 :manpage:`pthread_create(3)` to create threads instead.
3168 .. option:: wait_for=str
3170 If set, the current job won't be started until all workers of the specified
3171 waitee job are done.
3173 ``wait_for`` operates on the job name basis, so there are a few
3174 limitations. First, the waitee must be defined prior to the waiter job
3175 (meaning no forward references). Second, if a job is being referenced as a
3176 waitee, it must have a unique name (no duplicate waitees).
3178 .. option:: nice=int
3180 Run the job with the given nice value. See man :manpage:`nice(2)`.
3182 On Windows, values less than -15 set the process class to "High"; -1 through
3183 -15 set "Above Normal"; 1 through 15 "Below Normal"; and above 15 "Idle"
3186 .. option:: prio=int
3188 Set the I/O priority value of this job. Linux limits us to a positive value
3189 between 0 and 7, with 0 being the highest. See man
3190 :manpage:`ionice(1)`. Refer to an appropriate manpage for other operating
3191 systems since meaning of priority may differ. For per-command priority
3192 setting, see I/O engine specific :option:`cmdprio_percentage` and
3193 :option:`cmdprio` options.
3195 .. option:: prioclass=int
3197 Set the I/O priority class. See man :manpage:`ionice(1)`. For per-command
3198 priority setting, see I/O engine specific :option:`cmdprio_percentage`
3199 and :option:`cmdprio_class` options.
3201 .. option:: cpus_allowed=str
3203 Controls the same options as :option:`cpumask`, but accepts a textual
3204 specification of the permitted CPUs instead and CPUs are indexed from 0. So
3205 to use CPUs 0 and 5 you would specify ``cpus_allowed=0,5``. This option also
3206 allows a range of CPUs to be specified -- say you wanted a binding to CPUs
3207 0, 5, and 8 to 15, you would set ``cpus_allowed=0,5,8-15``.
3209 On Windows, when ``cpus_allowed`` is unset only CPUs from fio's current
3210 processor group will be used and affinity settings are inherited from the
3211 system. An fio build configured to target Windows 7 makes options that set
3212 CPUs processor group aware and values will set both the processor group
3213 and a CPU from within that group. For example, on a system where processor
3214 group 0 has 40 CPUs and processor group 1 has 32 CPUs, ``cpus_allowed``
3215 values between 0 and 39 will bind CPUs from processor group 0 and
3216 ``cpus_allowed`` values between 40 and 71 will bind CPUs from processor
3217 group 1. When using ``cpus_allowed_policy=shared`` all CPUs specified by a
3218 single ``cpus_allowed`` option must be from the same processor group. For
3219 Windows fio builds not built for Windows 7, CPUs will only be selected from
3220 (and be relative to) whatever processor group fio happens to be running in
3221 and CPUs from other processor groups cannot be used.
3223 .. option:: cpus_allowed_policy=str
3225 Set the policy of how fio distributes the CPUs specified by
3226 :option:`cpus_allowed` or :option:`cpumask`. Two policies are supported:
3229 All jobs will share the CPU set specified.
3231 Each job will get a unique CPU from the CPU set.
3233 **shared** is the default behavior, if the option isn't specified. If
3234 **split** is specified, then fio will assign one cpu per job. If not
3235 enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
3238 .. option:: cpumask=int
3240 Set the CPU affinity of this job. The parameter given is a bit mask of
3241 allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
3242 and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
3243 :manpage:`sched_setaffinity(2)`. This may not work on all supported
3244 operating systems or kernel versions. This option doesn't work well for a
3245 higher CPU count than what you can store in an integer mask, so it can only
3246 control cpus 1-32. For boxes with larger CPU counts, use
3247 :option:`cpus_allowed`.
3249 .. option:: numa_cpu_nodes=str
3251 Set this job running on specified NUMA nodes' CPUs. The arguments allow
3252 comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable
3253 NUMA options support, fio must be built on a system with libnuma-dev(el)
3256 .. option:: numa_mem_policy=str
3258 Set this job's memory policy and corresponding NUMA nodes. Format of the
3263 ``mode`` is one of the following memory policies: ``default``, ``prefer``,
3264 ``bind``, ``interleave`` or ``local``. For ``default`` and ``local`` memory
3265 policies, no node needs to be specified. For ``prefer``, only one node is
3266 allowed. For ``bind`` and ``interleave`` the ``nodelist`` may be as
3267 follows: a comma delimited list of numbers, A-B ranges, or `all`.
3269 .. option:: cgroup=str
3271 Add job to this control group. If it doesn't exist, it will be created. The
3272 system must have a mounted cgroup blkio mount point for this to work. If
3273 your system doesn't have it mounted, you can do so with::
3275 # mount -t cgroup -o blkio none /cgroup
3277 .. option:: cgroup_weight=int
3279 Set the weight of the cgroup to this value. See the documentation that comes
3280 with the kernel, allowed values are in the range of 100..1000.
3282 .. option:: cgroup_nodelete=bool
3284 Normally fio will delete the cgroups it has created after the job
3285 completion. To override this behavior and to leave cgroups around after the
3286 job completion, set ``cgroup_nodelete=1``. This can be useful if one wants
3287 to inspect various cgroup files after job completion. Default: false.
3289 .. option:: flow_id=int
3291 The ID of the flow. If not specified, it defaults to being a global
3292 flow. See :option:`flow`.
3294 .. option:: flow=int
3296 Weight in token-based flow control. If this value is used, then there is a
3297 'flow counter' which is used to regulate the proportion of activity between
3298 two or more jobs. Fio attempts to keep this flow counter near zero. The
3299 ``flow`` parameter stands for how much should be added or subtracted to the
3300 flow counter on each iteration of the main I/O loop. That is, if one job has
3301 ``flow=8`` and another job has ``flow=-1``, then there will be a roughly 1:8
3302 ratio in how much one runs vs the other.
3304 .. option:: flow_sleep=int
3306 The period of time, in microseconds, to wait after the flow counter
3307 has exceeded its proportion before retrying operations.
3309 .. option:: stonewall, wait_for_previous
3311 Wait for preceding jobs in the job file to exit, before starting this
3312 one. Can be used to insert serialization points in the job file. A stone
3313 wall also implies starting a new reporting group, see
3314 :option:`group_reporting`.
3318 By default, fio will continue running all other jobs when one job finishes.
3319 Sometimes this is not the desired action. Setting ``exitall`` will instead
3320 make fio terminate all jobs in the same group, as soon as one job of that
3323 .. option:: exit_what
3325 By default, fio will continue running all other jobs when one job finishes.
3326 Sometimes this is not the desired action. Setting ``exit_all`` will
3327 instead make fio terminate all jobs in the same group. The option
3328 ``exit_what`` allows to control which jobs get terminated when ``exitall`` is
3329 enabled. The default is ``group`` and does not change the behaviour of
3330 ``exitall``. The setting ``all`` terminates all jobs. The setting ``stonewall``
3331 terminates all currently running jobs across all groups and continues execution
3332 with the next stonewalled group.
3334 .. option:: exec_prerun=str
3336 Before running this job, issue the command specified through
3337 :manpage:`system(3)`. Output is redirected in a file called
3338 :file:`jobname.prerun.txt`.
3340 .. option:: exec_postrun=str
3342 After the job completes, issue the command specified though
3343 :manpage:`system(3)`. Output is redirected in a file called
3344 :file:`jobname.postrun.txt`.
3348 Instead of running as the invoking user, set the user ID to this value
3349 before the thread/process does any work.
3353 Set group ID, see :option:`uid`.
3359 .. option:: verify_only
3361 Do not perform specified workload, only verify data still matches previous
3362 invocation of this workload. This option allows one to check data multiple
3363 times at a later date without overwriting it. This option makes sense only
3364 for workloads that write data, and does not support workloads with the
3365 :option:`time_based` option set.
3367 .. option:: do_verify=bool
3369 Run the verify phase after a write phase. Only valid if :option:`verify` is
3372 .. option:: verify=str
3374 If writing to a file, fio can verify the file contents after each iteration
3375 of the job. Each verification method also implies verification of special
3376 header, which is written to the beginning of each block. This header also
3377 includes meta information, like offset of the block, block number, timestamp
3378 when block was written, etc. :option:`verify` can be combined with
3379 :option:`verify_pattern` option. The allowed values are:
3382 Use an md5 sum of the data area and store it in the header of
3386 Use an experimental crc64 sum of the data area and store it in the
3387 header of each block.
3390 Use a crc32c sum of the data area and store it in the header of
3391 each block. This will automatically use hardware acceleration
3392 (e.g. SSE4.2 on an x86 or CRC crypto extensions on ARM64) but will
3393 fall back to software crc32c if none is found. Generally the
3394 fastest checksum fio supports when hardware accelerated.
3400 Use a crc32 sum of the data area and store it in the header of each
3404 Use a crc16 sum of the data area and store it in the header of each
3408 Use a crc7 sum of the data area and store it in the header of each
3412 Use xxhash as the checksum function. Generally the fastest software
3413 checksum that fio supports.
3416 Use sha512 as the checksum function.
3419 Use sha256 as the checksum function.
3422 Use optimized sha1 as the checksum function.
3425 Use optimized sha3-224 as the checksum function.
3428 Use optimized sha3-256 as the checksum function.
3431 Use optimized sha3-384 as the checksum function.
3434 Use optimized sha3-512 as the checksum function.
3437 This option is deprecated, since now meta information is included in
3438 generic verification header and meta verification happens by
3439 default. For detailed information see the description of the
3440 :option:`verify` setting. This option is kept because of
3441 compatibility's sake with old configurations. Do not use it.
3444 Verify a strict pattern. Normally fio includes a header with some
3445 basic information and checksumming, but if this option is set, only
3446 the specific pattern set with :option:`verify_pattern` is verified.
3449 Only pretend to verify. Useful for testing internals with
3450 :option:`ioengine`\=null, not for much else.
3452 This option can be used for repeated burn-in tests of a system to make sure
3453 that the written data is also correctly read back. If the data direction
3454 given is a read or random read, fio will assume that it should verify a
3455 previously written file. If the data direction includes any form of write,
3456 the verify will be of the newly written data.
3458 To avoid false verification errors, do not use the norandommap option when
3459 verifying data with async I/O engines and I/O depths > 1. Or use the
3460 norandommap and the lfsr random generator together to avoid writing to the
3461 same offset with multiple outstanding I/Os.
3463 .. option:: verify_offset=int
3465 Swap the verification header with data somewhere else in the block before
3466 writing. It is swapped back before verifying.
3468 .. option:: verify_interval=int
3470 Write the verification header at a finer granularity than the
3471 :option:`blocksize`. It will be written for chunks the size of
3472 ``verify_interval``. :option:`blocksize` should divide this evenly.
3474 .. option:: verify_pattern=str
3476 If set, fio will fill the I/O buffers with this pattern. Fio defaults to
3477 filling with totally random bytes, but sometimes it's interesting to fill
3478 with a known pattern for I/O verification purposes. Depending on the width
3479 of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it can
3480 be either a decimal or a hex number). The ``verify_pattern`` if larger than
3481 a 32-bit quantity has to be a hex number that starts with either "0x" or
3482 "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o
3483 format, which means that for each block offset will be written and then
3484 verified back, e.g.::
3488 Or use combination of everything::
3490 verify_pattern=0xff%o"abcd"-12
3492 .. option:: verify_fatal=bool
3494 Normally fio will keep checking the entire contents before quitting on a
3495 block verification failure. If this option is set, fio will exit the job on
3496 the first observed failure. Default: false.
3498 .. option:: verify_dump=bool
3500 If set, dump the contents of both the original data block and the data block
3501 we read off disk to files. This allows later analysis to inspect just what
3502 kind of data corruption occurred. Off by default.
3504 .. option:: verify_async=int
3506 Fio will normally verify I/O inline from the submitting thread. This option
3507 takes an integer describing how many async offload threads to create for I/O
3508 verification instead, causing fio to offload the duty of verifying I/O
3509 contents to one or more separate threads. If using this offload option, even
3510 sync I/O engines can benefit from using an :option:`iodepth` setting higher
3511 than 1, as it allows them to have I/O in flight while verifies are running.
3512 Defaults to 0 async threads, i.e. verification is not asynchronous.
3514 .. option:: verify_async_cpus=str
3516 Tell fio to set the given CPU affinity on the async I/O verification
3517 threads. See :option:`cpus_allowed` for the format used.
3519 .. option:: verify_backlog=int
3521 Fio will normally verify the written contents of a job that utilizes verify
3522 once that job has completed. In other words, everything is written then
3523 everything is read back and verified. You may want to verify continually
3524 instead for a variety of reasons. Fio stores the meta data associated with
3525 an I/O block in memory, so for large verify workloads, quite a bit of memory
3526 would be used up holding this meta data. If this option is enabled, fio will
3527 write only N blocks before verifying these blocks.
3529 .. option:: verify_backlog_batch=int
3531 Control how many blocks fio will verify if :option:`verify_backlog` is
3532 set. If not set, will default to the value of :option:`verify_backlog`
3533 (meaning the entire queue is read back and verified). If
3534 ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all
3535 blocks will be verified, if ``verify_backlog_batch`` is larger than
3536 :option:`verify_backlog`, some blocks will be verified more than once.
3538 .. option:: verify_state_save=bool
3540 When a job exits during the write phase of a verify workload, save its
3541 current state. This allows fio to replay up until that point, if the verify
3542 state is loaded for the verify read phase. The format of the filename is,
3545 <type>-<jobname>-<jobindex>-verify.state.
3547 <type> is "local" for a local run, "sock" for a client/server socket
3548 connection, and "ip" (192.168.0.1, for instance) for a networked
3549 client/server connection. Defaults to true.
3551 .. option:: verify_state_load=bool
3553 If a verify termination trigger was used, fio stores the current write state
3554 of each thread. This can be used at verification time so that fio knows how
3555 far it should verify. Without this information, fio will run a full
3556 verification pass, according to the settings in the job file used. Default
3559 .. option:: trim_percentage=int
3561 Number of verify blocks to discard/trim.
3563 .. option:: trim_verify_zero=bool
3565 Verify that trim/discarded blocks are returned as zeros.
3567 .. option:: trim_backlog=int
3569 Trim after this number of blocks are written.
3571 .. option:: trim_backlog_batch=int
3573 Trim this number of I/O blocks.
3575 .. option:: experimental_verify=bool
3577 Enable experimental verification.
3582 .. option:: steadystate=str:float, ss=str:float
3584 Define the criterion and limit for assessing steady state performance. The
3585 first parameter designates the criterion whereas the second parameter sets
3586 the threshold. When the criterion falls below the threshold for the
3587 specified duration, the job will stop. For example, `iops_slope:0.1%` will
3588 direct fio to terminate the job when the least squares regression slope
3589 falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled
3590 this will apply to all jobs in the group. Below is the list of available
3591 steady state assessment criteria. All assessments are carried out using only
3592 data from the rolling collection window. Threshold limits can be expressed
3593 as a fixed value or as a percentage of the mean in the collection window.
3595 When using this feature, most jobs should include the :option:`time_based`
3596 and :option:`runtime` options or the :option:`loops` option so that fio does not
3597 stop running after it has covered the full size of the specified file(s) or device(s).
3600 Collect IOPS data. Stop the job if all individual IOPS measurements
3601 are within the specified limit of the mean IOPS (e.g., ``iops:2``
3602 means that all individual IOPS values must be within 2 of the mean,
3603 whereas ``iops:0.2%`` means that all individual IOPS values must be
3604 within 0.2% of the mean IOPS to terminate the job).
3607 Collect IOPS data and calculate the least squares regression
3608 slope. Stop the job if the slope falls below the specified limit.
3611 Collect bandwidth data. Stop the job if all individual bandwidth
3612 measurements are within the specified limit of the mean bandwidth.
3615 Collect bandwidth data and calculate the least squares regression
3616 slope. Stop the job if the slope falls below the specified limit.
3618 .. option:: steadystate_duration=time, ss_dur=time
3620 A rolling window of this duration will be used to judge whether steady state
3621 has been reached. Data will be collected once per second. The default is 0
3622 which disables steady state detection. When the unit is omitted, the
3623 value is interpreted in seconds.
3625 .. option:: steadystate_ramp_time=time, ss_ramp=time
3627 Allow the job to run for the specified duration before beginning data
3628 collection for checking the steady state job termination criterion. The
3629 default is 0. When the unit is omitted, the value is interpreted in seconds.
3632 Measurements and reporting
3633 ~~~~~~~~~~~~~~~~~~~~~~~~~~
3635 .. option:: per_job_logs=bool
3637 If set, this generates bw/clat/iops log with per file private filenames. If
3638 not set, jobs with identical names will share the log filename. Default:
3641 .. option:: group_reporting
3643 It may sometimes be interesting to display statistics for groups of jobs as
3644 a whole instead of for each individual job. This is especially true if
3645 :option:`numjobs` is used; looking at individual thread/process output
3646 quickly becomes unwieldy. To see the final report per-group instead of
3647 per-job, use :option:`group_reporting`. Jobs in a file will be part of the
3648 same reporting group, unless if separated by a :option:`stonewall`, or by
3649 using :option:`new_group`.
3651 .. option:: new_group
3653 Start a new reporting group. See: :option:`group_reporting`. If not given,
3654 all jobs in a file will be part of the same reporting group, unless
3655 separated by a :option:`stonewall`.
3657 .. option:: stats=bool
3659 By default, fio collects and shows final output results for all jobs
3660 that run. If this option is set to 0, then fio will ignore it in
3661 the final stat output.
3663 .. option:: write_bw_log=str
3665 If given, write a bandwidth log for this job. Can be used to store data of
3666 the bandwidth of the jobs in their lifetime.
3668 If no str argument is given, the default filename of
3669 :file:`jobname_type.x.log` is used. Even when the argument is given, fio
3670 will still append the type of log. So if one specifies::
3674 The actual log name will be :file:`foo_bw.x.log` where `x` is the index
3675 of the job (`1..N`, where `N` is the number of jobs). If
3676 :option:`per_job_logs` is false, then the filename will not include the
3679 The included :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
3680 text files into nice graphs. See `Log File Formats`_ for how data is
3681 structured within the file.
3683 .. option:: write_lat_log=str
3685 Same as :option:`write_bw_log`, except this option creates I/O
3686 submission (e.g., :file:`name_slat.x.log`), completion (e.g.,
3687 :file:`name_clat.x.log`), and total (e.g., :file:`name_lat.x.log`)
3688 latency files instead. See :option:`write_bw_log` for details about
3689 the filename format and `Log File Formats`_ for how data is structured
3692 .. option:: write_hist_log=str
3694 Same as :option:`write_bw_log` but writes an I/O completion latency
3695 histogram file (e.g., :file:`name_hist.x.log`) instead. Note that this
3696 file will be empty unless :option:`log_hist_msec` has also been set.
3697 See :option:`write_bw_log` for details about the filename format and
3698 `Log File Formats`_ for how data is structured within the file.
3700 .. option:: write_iops_log=str
3702 Same as :option:`write_bw_log`, but writes an IOPS file (e.g.
3703 :file:`name_iops.x.log`) instead. Because fio defaults to individual
3704 I/O logging, the value entry in the IOPS log will be 1 unless windowed
3705 logging (see :option:`log_avg_msec`) has been enabled. See
3706 :option:`write_bw_log` for details about the filename format and `Log
3707 File Formats`_ for how data is structured within the file.
3709 .. option:: log_entries=int
3711 By default, fio will log an entry in the iops, latency, or bw log for
3712 every I/O that completes. The initial number of I/O log entries is 1024.
3713 When the log entries are all used, new log entries are dynamically
3714 allocated. This dynamic log entry allocation may negatively impact
3715 time-related statistics such as I/O tail latencies (e.g. 99.9th percentile
3716 completion latency). This option allows specifying a larger initial
3717 number of log entries to avoid run-time allocations of new log entries,
3718 resulting in more precise time-related I/O statistics.
3719 Also see :option:`log_avg_msec`. Defaults to 1024.
3721 .. option:: log_avg_msec=int
3723 By default, fio will log an entry in the iops, latency, or bw log for every
3724 I/O that completes. When writing to the disk log, that can quickly grow to a
3725 very large size. Setting this option makes fio average the each log entry
3726 over the specified period of time, reducing the resolution of the log. See
3727 :option:`log_max_value` as well. Defaults to 0, logging all entries.
3728 Also see `Log File Formats`_.
3730 .. option:: log_hist_msec=int
3732 Same as :option:`log_avg_msec`, but logs entries for completion latency
3733 histograms. Computing latency percentiles from averages of intervals using
3734 :option:`log_avg_msec` is inaccurate. Setting this option makes fio log
3735 histogram entries over the specified period of time, reducing log sizes for
3736 high IOPS devices while retaining percentile accuracy. See
3737 :option:`log_hist_coarseness` and :option:`write_hist_log` as well.
3738 Defaults to 0, meaning histogram logging is disabled.
3740 .. option:: log_hist_coarseness=int
3742 Integer ranging from 0 to 6, defining the coarseness of the resolution of
3743 the histogram logs enabled with :option:`log_hist_msec`. For each increment
3744 in coarseness, fio outputs half as many bins. Defaults to 0, for which
3745 histogram logs contain 1216 latency bins. See :option:`write_hist_log`
3746 and `Log File Formats`_.
3748 .. option:: log_max_value=bool
3750 If :option:`log_avg_msec` is set, fio logs the average over that window. If
3751 you instead want to log the maximum value, set this option to 1. Defaults to
3752 0, meaning that averaged values are logged.
3754 .. option:: log_offset=bool
3756 If this is set, the iolog options will include the byte offset for the I/O
3757 entry as well as the other data values. Defaults to 0 meaning that
3758 offsets are not present in logs. Also see `Log File Formats`_.
3760 .. option:: log_compression=int
3762 If this is set, fio will compress the I/O logs as it goes, to keep the
3763 memory footprint lower. When a log reaches the specified size, that chunk is
3764 removed and compressed in the background. Given that I/O logs are fairly
3765 highly compressible, this yields a nice memory savings for longer runs. The
3766 downside is that the compression will consume some background CPU cycles, so
3767 it may impact the run. This, however, is also true if the logging ends up
3768 consuming most of the system memory. So pick your poison. The I/O logs are
3769 saved normally at the end of a run, by decompressing the chunks and storing
3770 them in the specified log file. This feature depends on the availability of
3773 .. option:: log_compression_cpus=str
3775 Define the set of CPUs that are allowed to handle online log compression for
3776 the I/O jobs. This can provide better isolation between performance
3777 sensitive jobs, and background compression work. See
3778 :option:`cpus_allowed` for the format used.
3780 .. option:: log_store_compressed=bool
3782 If set, fio will store the log files in a compressed format. They can be
3783 decompressed with fio, using the :option:`--inflate-log` command line
3784 parameter. The files will be stored with a :file:`.fz` suffix.
3786 .. option:: log_unix_epoch=bool
3788 If set, fio will log Unix timestamps to the log files produced by enabling
3789 write_type_log for each log type, instead of the default zero-based
3792 .. option:: log_alternate_epoch=bool
3794 If set, fio will log timestamps based on the epoch used by the clock specified
3795 in the log_alternate_epoch_clock_id option, to the log files produced by
3796 enabling write_type_log for each log type, instead of the default zero-based
3799 .. option:: log_alternate_epoch_clock_id=int
3801 Specifies the clock_id to be used by clock_gettime to obtain the alternate epoch
3802 if either log_unix_epoch or log_alternate_epoch are true. Otherwise has no
3803 effect. Default value is 0, or CLOCK_REALTIME.
3805 .. option:: block_error_percentiles=bool
3807 If set, record errors in trim block-sized units from writes and trims and
3808 output a histogram of how many trims it took to get to errors, and what kind
3809 of error was encountered.
3811 .. option:: bwavgtime=int
3813 Average the calculated bandwidth over the given time. Value is specified in
3814 milliseconds. If the job also does bandwidth logging through
3815 :option:`write_bw_log`, then the minimum of this option and
3816 :option:`log_avg_msec` will be used. Default: 500ms.
3818 .. option:: iopsavgtime=int
3820 Average the calculated IOPS over the given time. Value is specified in
3821 milliseconds. If the job also does IOPS logging through
3822 :option:`write_iops_log`, then the minimum of this option and
3823 :option:`log_avg_msec` will be used. Default: 500ms.
3825 .. option:: disk_util=bool
3827 Generate disk utilization statistics, if the platform supports it.
3830 .. option:: disable_lat=bool
3832 Disable measurements of total latency numbers. Useful only for cutting back
3833 the number of calls to :manpage:`gettimeofday(2)`, as that does impact
3834 performance at really high IOPS rates. Note that to really get rid of a
3835 large amount of these calls, this option must be used with
3836 :option:`disable_slat` and :option:`disable_bw_measurement` as well.
3838 .. option:: disable_clat=bool
3840 Disable measurements of completion latency numbers. See
3841 :option:`disable_lat`.
3843 .. option:: disable_slat=bool
3845 Disable measurements of submission latency numbers. See
3846 :option:`disable_lat`.
3848 .. option:: disable_bw_measurement=bool, disable_bw=bool
3850 Disable measurements of throughput/bandwidth numbers. See
3851 :option:`disable_lat`.
3853 .. option:: slat_percentiles=bool
3855 Report submission latency percentiles. Submission latency is not recorded
3856 for synchronous ioengines.
3858 .. option:: clat_percentiles=bool
3860 Report completion latency percentiles.
3862 .. option:: lat_percentiles=bool
3864 Report total latency percentiles. Total latency is the sum of submission
3865 latency and completion latency.
3867 .. option:: percentile_list=float_list
3869 Overwrite the default list of percentiles for latencies and the block error
3870 histogram. Each number is a floating point number in the range (0,100], and
3871 the maximum length of the list is 20. Use ``:`` to separate the numbers. For
3872 example, ``--percentile_list=99.5:99.9`` will cause fio to report the
3873 latency durations below which 99.5% and 99.9% of the observed latencies fell,
3876 .. option:: significant_figures=int
3878 If using :option:`--output-format` of `normal`, set the significant
3879 figures to this value. Higher values will yield more precise IOPS and
3880 throughput units, while lower values will round. Requires a minimum
3881 value of 1 and a maximum value of 10. Defaults to 4.
3887 .. option:: exitall_on_error
3889 When one job finishes in error, terminate the rest. The default is to wait
3890 for each job to finish.
3892 .. option:: continue_on_error=str
3894 Normally fio will exit the job on the first observed failure. If this option
3895 is set, fio will continue the job when there is a 'non-fatal error' (EIO or
3896 EILSEQ) until the runtime is exceeded or the I/O size specified is
3897 completed. If this option is used, there are two more stats that are
3898 appended, the total error count and the first error. The error field given
3899 in the stats is the first error that was hit during the run.
3901 The allowed values are:
3904 Exit on any I/O or verify errors.
3907 Continue on read errors, exit on all others.
3910 Continue on write errors, exit on all others.
3913 Continue on any I/O error, exit on all others.
3916 Continue on verify errors, exit on all others.
3919 Continue on all errors.
3922 Backward-compatible alias for 'none'.
3925 Backward-compatible alias for 'all'.
3927 .. option:: ignore_error=str
3929 Sometimes you want to ignore some errors during test in that case you can
3930 specify error list for each error type, instead of only being able to
3931 ignore the default 'non-fatal error' using :option:`continue_on_error`.
3932 ``ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST`` errors for
3933 given error type is separated with ':'. Error may be symbol ('ENOSPC',
3934 'ENOMEM') or integer. Example::
3936 ignore_error=EAGAIN,ENOSPC:122
3938 This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from
3939 WRITE. This option works by overriding :option:`continue_on_error` with
3940 the list of errors for each error type if any.
3942 .. option:: error_dump=bool
3944 If set dump every error even if it is non fatal, true by default. If
3945 disabled only fatal error will be dumped.
3947 Running predefined workloads
3948 ----------------------------
3950 Fio includes predefined profiles that mimic the I/O workloads generated by
3953 .. option:: profile=str
3955 The predefined workload to run. Current profiles are:
3958 Threaded I/O bench (tiotest/tiobench) like workload.
3961 Aerospike Certification Tool (ACT) like workload.
3963 To view a profile's additional options use :option:`--cmdhelp` after specifying
3964 the profile. For example::
3966 $ fio --profile=act --cmdhelp
3971 .. option:: device-names=str
3976 .. option:: load=int
3979 ACT load multiplier. Default: 1.
3981 .. option:: test-duration=time
3984 How long the entire test takes to run. When the unit is omitted, the value
3985 is given in seconds. Default: 24h.
3987 .. option:: threads-per-queue=int
3990 Number of read I/O threads per device. Default: 8.
3992 .. option:: read-req-num-512-blocks=int
3995 Number of 512B blocks to read at the time. Default: 3.
3997 .. option:: large-block-op-kbytes=int
4000 Size of large block ops in KiB (writes). Default: 131072.
4005 Set to run ACT prep phase.
4007 Tiobench profile options
4008 ~~~~~~~~~~~~~~~~~~~~~~~~
4010 .. option:: size=str
4015 .. option:: block=int
4018 Block size in bytes. Default: 4096.
4020 .. option:: numruns=int
4030 .. option:: threads=int
4035 Interpreting the output
4036 -----------------------
4039 Example output was based on the following:
4040 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --time_based \
4041 --rate=1256k --bs=14K --name=quick --runtime=1s --name=mixed \
4042 --runtime=2m --rw=rw
4044 Fio spits out a lot of output. While running, fio will display the status of the
4045 jobs created. An example of that would be::
4047 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]
4049 The characters inside the first set of square brackets denote the current status of
4050 each thread. The first character is the first job defined in the job file, and so
4051 forth. The possible values (in typical life cycle order) are:
4053 +------+-----+-----------------------------------------------------------+
4055 +======+=====+===========================================================+
4056 | P | | Thread setup, but not started. |
4057 +------+-----+-----------------------------------------------------------+
4058 | C | | Thread created. |
4059 +------+-----+-----------------------------------------------------------+
4060 | I | | Thread initialized, waiting or generating necessary data. |
4061 +------+-----+-----------------------------------------------------------+
4062 | | p | Thread running pre-reading file(s). |
4063 +------+-----+-----------------------------------------------------------+
4064 | | / | Thread is in ramp period. |
4065 +------+-----+-----------------------------------------------------------+
4066 | | R | Running, doing sequential reads. |
4067 +------+-----+-----------------------------------------------------------+
4068 | | r | Running, doing random reads. |
4069 +------+-----+-----------------------------------------------------------+
4070 | | W | Running, doing sequential writes. |
4071 +------+-----+-----------------------------------------------------------+
4072 | | w | Running, doing random writes. |
4073 +------+-----+-----------------------------------------------------------+
4074 | | M | Running, doing mixed sequential reads/writes. |
4075 +------+-----+-----------------------------------------------------------+
4076 | | m | Running, doing mixed random reads/writes. |
4077 +------+-----+-----------------------------------------------------------+
4078 | | D | Running, doing sequential trims. |
4079 +------+-----+-----------------------------------------------------------+
4080 | | d | Running, doing random trims. |
4081 +------+-----+-----------------------------------------------------------+
4082 | | F | Running, currently waiting for :manpage:`fsync(2)`. |
4083 +------+-----+-----------------------------------------------------------+
4084 | | V | Running, doing verification of written data. |
4085 +------+-----+-----------------------------------------------------------+
4086 | f | | Thread finishing. |
4087 +------+-----+-----------------------------------------------------------+
4088 | E | | Thread exited, not reaped by main thread yet. |
4089 +------+-----+-----------------------------------------------------------+
4090 | _ | | Thread reaped. |
4091 +------+-----+-----------------------------------------------------------+
4092 | X | | Thread reaped, exited with an error. |
4093 +------+-----+-----------------------------------------------------------+
4094 | K | | Thread reaped, exited due to signal. |
4095 +------+-----+-----------------------------------------------------------+
4098 Example output was based on the following:
4099 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --runtime=58m \
4100 --time_based --rate=2512k --bs=256K --numjobs=10 \
4101 --name=readers --rw=read --name=writers --rw=write
4103 Fio will condense the thread string as not to take up more space on the command
4104 line than needed. For instance, if you have 10 readers and 10 writers running,
4105 the output would look like this::
4107 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]
4109 Note that the status string is displayed in order, so it's possible to tell which of
4110 the jobs are currently doing what. In the example above this means that jobs 1--10
4111 are readers and 11--20 are writers.
4113 The other values are fairly self explanatory -- number of threads currently
4114 running and doing I/O, the number of currently open files (f=), the estimated
4115 completion percentage, the rate of I/O since last check (read speed listed first,
4116 then write speed and optionally trim speed) in terms of bandwidth and IOPS,
4117 and time to completion for the current running group. It's impossible to estimate
4118 runtime of the following groups (if any).
4121 Example output was based on the following:
4122 TZ=UTC fio --iodepth=16 --ioengine=posixaio --filename=/tmp/fiofile \
4123 --direct=1 --size=100M --time_based --runtime=50s --rate_iops=89 \
4124 --bs=7K --name=Client1 --rw=write
4126 When fio is done (or interrupted by :kbd:`Ctrl-C`), it will show the data for
4127 each thread, group of threads, and disks in that order. For each overall thread (or
4128 group) the output looks like::
4130 Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
4131 write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
4132 slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
4133 clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
4134 lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
4135 clat percentiles (usec):
4136 | 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
4137 | 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
4138 | 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
4139 | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
4141 bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
4142 iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
4143 lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
4144 lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
4145 lat (msec) : 100=0.65%
4146 cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
4147 IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
4148 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
4149 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
4150 issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
4151 latency : target=0, window=0, percentile=100.00%, depth=8
4153 The job name (or first job's name when using :option:`group_reporting`) is printed,
4154 along with the group id, count of jobs being aggregated, last error id seen (which
4155 is 0 when there are no errors), pid/tid of that thread and the time the job/group
4156 completed. Below are the I/O statistics for each data direction performed (showing
4157 writes in the example above). In the order listed, they denote:
4160 The string before the colon shows the I/O direction the statistics
4161 are for. **IOPS** is the average I/Os performed per second. **BW**
4162 is the average bandwidth rate shown as: value in power of 2 format
4163 (value in power of 10 format). The last two values show: (**total
4164 I/O performed** in power of 2 format / **runtime** of that thread).
4167 Submission latency (**min** being the minimum, **max** being the
4168 maximum, **avg** being the average, **stdev** being the standard
4169 deviation). This is the time from when fio initialized the I/O
4170 to submission. For synchronous ioengines this includes the time
4171 up until just before the ioengine's queue function is called.
4172 For asynchronous ioengines this includes the time up through the
4173 completion of the ioengine's queue function (and commit function
4174 if it is defined). For sync I/O this row is not displayed as the
4175 slat is negligible. This value can be in nanoseconds,
4176 microseconds or milliseconds --- fio will choose the most
4177 appropriate base and print that (in the example above
4178 nanoseconds was the best scale). Note: in :option:`--minimal`
4179 mode latencies are always expressed in microseconds.
4182 Completion latency. Same names as slat, this denotes the time from
4183 submission to completion of the I/O pieces. For sync I/O, this
4184 represents the time from when the I/O was submitted to the
4185 operating system to when it was completed. For asynchronous
4186 ioengines this is the time from when the ioengine's queue (and
4187 commit if available) functions were completed to when the I/O's
4188 completion was reaped by fio.
4191 Total latency. Same names as slat and clat, this denotes the time from
4192 when fio created the I/O unit to completion of the I/O operation.
4193 It is the sum of submission and completion latency.
4196 Bandwidth statistics based on samples. Same names as the xlat stats,
4197 but also includes the number of samples taken (**samples**) and an
4198 approximate percentage of total aggregate bandwidth this thread
4199 received in its group (**per**). This last value is only really
4200 useful if the threads in this group are on the same disk, since they
4201 are then competing for disk access.
4204 IOPS statistics based on samples. Same names as bw.
4206 **lat (nsec/usec/msec)**
4207 The distribution of I/O completion latencies. This is the time from when
4208 I/O leaves fio and when it gets completed. Unlike the separate
4209 read/write/trim sections above, the data here and in the remaining
4210 sections apply to all I/Os for the reporting group. 250=0.04% means that
4211 0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11%
4212 of the I/Os required 250 to 499us for completion.
4215 CPU usage. User and system time, along with the number of context
4216 switches this thread went through, usage of system and user time, and
4217 finally the number of major and minor page faults. The CPU utilization
4218 numbers are averages for the jobs in that reporting group, while the
4219 context and fault counters are summed.
4222 The distribution of I/O depths over the job lifetime. The numbers are
4223 divided into powers of 2 and each entry covers depths from that value
4224 up to those that are lower than the next entry -- e.g., 16= covers
4225 depths from 16 to 31. Note that the range covered by a depth
4226 distribution entry can be different to the range covered by the
4227 equivalent submit/complete distribution entry.
4230 How many pieces of I/O were submitting in a single submit call. Each
4231 entry denotes that amount and below, until the previous entry -- e.g.,
4232 16=100% means that we submitted anywhere between 9 to 16 I/Os per submit
4233 call. Note that the range covered by a submit distribution entry can
4234 be different to the range covered by the equivalent depth distribution
4238 Like the above submit number, but for completions instead.
4241 The number of read/write/trim requests issued, and how many of them were
4245 These values are for :option:`latency_target` and related options. When
4246 these options are engaged, this section describes the I/O depth required
4247 to meet the specified latency target.
4250 Example output was based on the following:
4251 TZ=UTC fio --ioengine=null --iodepth=2 --size=100M --numjobs=2 \
4252 --rate_process=poisson --io_limit=32M --name=read --bs=128k \
4253 --rate=11M --name=write --rw=write --bs=2k --rate=700k
4255 After each client has been listed, the group statistics are printed. They
4256 will look like this::
4258 Run status group 0 (all jobs):
4259 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
4260 WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
4262 For each data direction it prints:
4265 Aggregate bandwidth of threads in this group followed by the
4266 minimum and maximum bandwidth of all the threads in this group.
4267 Values outside of brackets are power-of-2 format and those
4268 within are the equivalent value in a power-of-10 format.
4270 Aggregate I/O performed of all threads in this group. The
4271 format is the same as bw.
4273 The smallest and longest runtimes of the threads in this group.
4275 And finally, the disk statistics are printed. This is Linux specific. They will look like this::
4277 Disk stats (read/write):
4278 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
4280 Each value is printed for both reads and writes, with reads first. The
4284 Number of I/Os performed by all groups.
4286 Number of merges performed by the I/O scheduler.
4288 Number of ticks we kept the disk busy.
4290 Total time spent in the disk queue.
4292 The disk utilization. A value of 100% means we kept the disk
4293 busy constantly, 50% would be a disk idling half of the time.
4295 It is also possible to get fio to dump the current output while it is running,
4296 without terminating the job. To do that, send fio the **USR1** signal. You can
4297 also get regularly timed dumps by using the :option:`--status-interval`
4298 parameter, or by creating a file in :file:`/tmp` named
4299 :file:`fio-dump-status`. If fio sees this file, it will unlink it and dump the
4300 current output status.
4306 For scripted usage where you typically want to generate tables or graphs of the
4307 results, fio can output the results in a semicolon separated format. The format
4308 is one long line of values, such as::
4310 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%
4311 A description of this job goes here.
4313 The job description (if provided) follows on a second line for terse v2.
4314 It appears on the same line for other terse versions.
4316 To enable terse output, use the :option:`--minimal` or
4317 :option:`--output-format`\=terse command line options. The
4318 first value is the version of the terse output format. If the output has to be
4319 changed for some reason, this number will be incremented by 1 to signify that
4322 Split up, the format is as follows (comments in brackets denote when a
4323 field was introduced or whether it's specific to some terse version):
4327 terse version, fio version [v3], jobname, groupid, error
4331 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
4332 Submission latency: min, max, mean, stdev (usec)
4333 Completion latency: min, max, mean, stdev (usec)
4334 Completion latency percentiles: 20 fields (see below)
4335 Total latency: min, max, mean, stdev (usec)
4336 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
4337 IOPS [v5]: min, max, mean, stdev, number of samples
4343 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
4344 Submission latency: min, max, mean, stdev (usec)
4345 Completion latency: min, max, mean, stdev (usec)
4346 Completion latency percentiles: 20 fields (see below)
4347 Total latency: min, max, mean, stdev (usec)
4348 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
4349 IOPS [v5]: min, max, mean, stdev, number of samples
4351 TRIM status [all but version 3]:
4353 Fields are similar to READ/WRITE status.
4357 user, system, context switches, major faults, minor faults
4361 <=1, 2, 4, 8, 16, 32, >=64
4363 I/O latencies microseconds::
4365 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
4367 I/O latencies milliseconds::
4369 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
4371 Disk utilization [v3]::
4373 disk name, read ios, write ios, read merges, write merges, read ticks, write ticks,
4374 time spent in queue, disk utilization percentage
4376 Additional Info (dependent on continue_on_error, default off)::
4378 total # errors, first error code
4380 Additional Info (dependent on description being set)::
4384 Completion latency percentiles can be a grouping of up to 20 sets, so for the
4385 terse output fio writes all of them. Each field will look like this::
4389 which is the Xth percentile, and the `usec` latency associated with it.
4391 For `Disk utilization`, all disks used by fio are shown. So for each disk there
4392 will be a disk utilization section.
4394 Below is a single line containing short names for each of the fields in the
4395 minimal output v3, separated by semicolons::
4397 terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth_kb;read_iops;read_runtime_ms;read_slat_min_us;read_slat_max_us;read_slat_mean_us;read_slat_dev_us;read_clat_min_us;read_clat_max_us;read_clat_mean_us;read_clat_dev_us;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min_us;read_lat_max_us;read_lat_mean_us;read_lat_dev_us;read_bw_min_kb;read_bw_max_kb;read_bw_agg_pct;read_bw_mean_kb;read_bw_dev_kb;write_kb;write_bandwidth_kb;write_iops;write_runtime_ms;write_slat_min_us;write_slat_max_us;write_slat_mean_us;write_slat_dev_us;write_clat_min_us;write_clat_max_us;write_clat_mean_us;write_clat_dev_us;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min_us;write_lat_max_us;write_lat_mean_us;write_lat_dev_us;write_bw_min_kb;write_bw_max_kb;write_bw_agg_pct;write_bw_mean_kb;write_bw_dev_kb;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
4399 In client/server mode terse output differs from what appears when jobs are run
4400 locally. Disk utilization data is omitted from the standard terse output and
4401 for v3 and later appears on its own separate line at the end of each terse
4408 The `json` output format is intended to be both human readable and convenient
4409 for automated parsing. For the most part its sections mirror those of the
4410 `normal` output. The `runtime` value is reported in msec and the `bw` value is
4411 reported in 1024 bytes per second units.
4417 The `json+` output format is identical to the `json` output format except that it
4418 adds a full dump of the completion latency bins. Each `bins` object contains a
4419 set of (key, value) pairs where keys are latency durations and values count how
4420 many I/Os had completion latencies of the corresponding duration. For example,
4423 "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... }
4425 This data indicates that one I/O required 87,552ns to complete, two I/Os required
4426 100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
4428 Also included with fio is a Python script `fio_jsonplus_clat2csv` that takes
4429 json+ output and generates CSV-formatted latency data suitable for plotting.
4431 The latency durations actually represent the midpoints of latency intervals.
4432 For details refer to :file:`stat.h`.
4438 There are two trace file format that you can encounter. The older (v1) format is
4439 unsupported since version 1.20-rc3 (March 2008). It will still be described
4440 below in case that you get an old trace and want to understand it.
4442 In any case the trace is a simple text file with a single action per line.
4445 Trace file format v1
4446 ~~~~~~~~~~~~~~~~~~~~
4448 Each line represents a single I/O action in the following format::
4452 where `rw=0/1` for read/write, and the `offset` and `length` entries being in bytes.
4454 This format is not supported in fio versions >= 1.20-rc3.
4457 Trace file format v2
4458 ~~~~~~~~~~~~~~~~~~~~
4460 The second version of the trace file format was added in fio version 1.17. It
4461 allows to access more then one file per trace and has a bigger set of possible
4464 The first line of the trace file has to be::
4468 Following this can be lines in two different formats, which are described below.
4470 The file management format::
4474 The `filename` is given as an absolute path. The `action` can be one of these:
4477 Add the given `filename` to the trace.
4479 Open the file with the given `filename`. The `filename` has to have
4480 been added with the **add** action before.
4482 Close the file with the given `filename`. The file has to have been
4486 The file I/O action format::
4488 filename action offset length
4490 The `filename` is given as an absolute path, and has to have been added and
4491 opened before it can be used with this format. The `offset` and `length` are
4492 given in bytes. The `action` can be one of these:
4495 Wait for `offset` microseconds. Everything below 100 is discarded.
4496 The time is relative to the previous `wait` statement. Note that
4497 action `wait` is not allowed as of version 3, as the same behavior
4498 can be achieved using timestamps.
4500 Read `length` bytes beginning from `offset`.
4502 Write `length` bytes beginning from `offset`.
4504 :manpage:`fsync(2)` the file.
4506 :manpage:`fdatasync(2)` the file.
4508 Trim the given file from the given `offset` for `length` bytes.
4511 Trace file format v3
4512 ~~~~~~~~~~~~~~~~~~~~
4514 The third version of the trace file format was added in fio version 3.31. It
4515 forces each action to have a timestamp associated with it.
4517 The first line of the trace file has to be::
4521 Following this can be lines in two different formats, which are described below.
4523 The file management format::
4525 timestamp filename action
4527 The file I/O action format::
4529 timestamp filename action offset length
4531 The `timestamp` is relative to the beginning of the run (ie starts at 0). The
4532 `filename`, `action`, `offset` and `length` are identical to version 2, except
4533 that version 3 does not allow the `wait` action.
4536 I/O Replay - Merging Traces
4537 ---------------------------
4539 Colocation is a common practice used to get the most out of a machine.
4540 Knowing which workloads play nicely with each other and which ones don't is
4541 a much harder task. While fio can replay workloads concurrently via multiple
4542 jobs, it leaves some variability up to the scheduler making results harder to
4543 reproduce. Merging is a way to make the order of events consistent.
4545 Merging is integrated into I/O replay and done when a
4546 :option:`merge_blktrace_file` is specified. The list of files passed to
4547 :option:`read_iolog` go through the merge process and output a single file
4548 stored to the specified file. The output file is passed on as if it were the
4549 only file passed to :option:`read_iolog`. An example would look like::
4551 $ fio --read_iolog="<file1>:<file2>" --merge_blktrace_file="<output_file>"
4553 Creating only the merged file can be done by passing the command line argument
4554 :option:`--merge-blktrace-only`.
4556 Scaling traces can be done to see the relative impact of any particular trace
4557 being slowed down or sped up. :option:`merge_blktrace_scalars` takes in a colon
4558 separated list of percentage scalars. It is index paired with the files passed
4559 to :option:`read_iolog`.
4561 With scaling, it may be desirable to match the running time of all traces.
4562 This can be done with :option:`merge_blktrace_iters`. It is index paired with
4563 :option:`read_iolog` just like :option:`merge_blktrace_scalars`.
4565 In an example, given two traces, A and B, each 60s long. If we want to see
4566 the impact of trace A issuing IOs twice as fast and repeat trace A over the
4567 runtime of trace B, the following can be done::
4569 $ fio --read_iolog="<trace_a>:"<trace_b>" --merge_blktrace_file"<output_file>" --merge_blktrace_scalars="50:100" --merge_blktrace_iters="2:1"
4571 This runs trace A at 2x the speed twice for approximately the same runtime as
4572 a single run of trace B.
4575 CPU idleness profiling
4576 ----------------------
4578 In some cases, we want to understand CPU overhead in a test. For example, we
4579 test patches for the specific goodness of whether they reduce CPU usage.
4580 Fio implements a balloon approach to create a thread per CPU that runs at idle
4581 priority, meaning that it only runs when nobody else needs the cpu.
4582 By measuring the amount of work completed by the thread, idleness of each CPU
4583 can be derived accordingly.
4585 An unit work is defined as touching a full page of unsigned characters. Mean and
4586 standard deviation of time to complete an unit work is reported in "unit work"
4587 section. Options can be chosen to report detailed percpu idleness or overall
4588 system idleness by aggregating percpu stats.
4591 Verification and triggers
4592 -------------------------
4594 Fio is usually run in one of two ways, when data verification is done. The first
4595 is a normal write job of some sort with verify enabled. When the write phase has
4596 completed, fio switches to reads and verifies everything it wrote. The second
4597 model is running just the write phase, and then later on running the same job
4598 (but with reads instead of writes) to repeat the same I/O patterns and verify
4599 the contents. Both of these methods depend on the write phase being completed,
4600 as fio otherwise has no idea how much data was written.
4602 With verification triggers, fio supports dumping the current write state to
4603 local files. Then a subsequent read verify workload can load this state and know
4604 exactly where to stop. This is useful for testing cases where power is cut to a
4605 server in a managed fashion, for instance.
4607 A verification trigger consists of two things:
4609 1) Storing the write state of each job.
4610 2) Executing a trigger command.
4612 The write state is relatively small, on the order of hundreds of bytes to single
4613 kilobytes. It contains information on the number of completions done, the last X
4616 A trigger is invoked either through creation ('touch') of a specified file in
4617 the system, or through a timeout setting. If fio is run with
4618 :option:`--trigger-file`\= :file:`/tmp/trigger-file`, then it will continually
4619 check for the existence of :file:`/tmp/trigger-file`. When it sees this file, it
4620 will fire off the trigger (thus saving state, and executing the trigger
4623 For client/server runs, there's both a local and remote trigger. If fio is
4624 running as a server backend, it will send the job states back to the client for
4625 safe storage, then execute the remote trigger, if specified. If a local trigger
4626 is specified, the server will still send back the write state, but the client
4627 will then execute the trigger.
4629 Verification trigger example
4630 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4632 Let's say we want to run a powercut test on the remote Linux machine 'server'.
4633 Our write workload is in :file:`write-test.fio`. We want to cut power to 'server' at
4634 some point during the run, and we'll run this test from the safety or our local
4635 machine, 'localbox'. On the server, we'll start the fio backend normally::
4637 server# fio --server
4639 and on the client, we'll fire off the workload::
4641 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
4643 We set :file:`/tmp/my-trigger` as the trigger file, and we tell fio to execute::
4645 echo b > /proc/sysrq-trigger
4647 on the server once it has received the trigger and sent us the write state. This
4648 will work, but it's not **really** cutting power to the server, it's merely
4649 abruptly rebooting it. If we have a remote way of cutting power to the server
4650 through IPMI or similar, we could do that through a local trigger command
4651 instead. Let's assume we have a script that does IPMI reboot of a given hostname,
4652 ipmi-reboot. On localbox, we could then have run fio with a local trigger
4655 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
4657 For this case, fio would wait for the server to send us the write state, then
4658 execute ``ipmi-reboot server`` when that happened.
4660 Loading verify state
4661 ~~~~~~~~~~~~~~~~~~~~
4663 To load stored write state, a read verification job file must contain the
4664 :option:`verify_state_load` option. If that is set, fio will load the previously
4665 stored state. For a local fio run this is done by loading the files directly,
4666 and on a client/server run, the server backend will ask the client to send the
4667 files over and load them from there.
4673 Fio supports a variety of log file formats, for logging latencies, bandwidth,
4674 and IOPS. The logs share a common format, which looks like this:
4676 *time* (`msec`), *value*, *data direction*, *block size* (`bytes`),
4677 *offset* (`bytes`), *command priority*
4679 *Time* for the log entry is always in milliseconds. The *value* logged depends
4680 on the type of log, it will be one of the following:
4683 Value is latency in nsecs
4689 *Data direction* is one of the following:
4698 The entry's *block size* is always in bytes. The *offset* is the position in bytes
4699 from the start of the file for that particular I/O. The logging of the offset can be
4700 toggled with :option:`log_offset`.
4702 *Command priority* is 0 for normal priority and 1 for high priority. This is controlled
4703 by the ioengine specific :option:`cmdprio_percentage`.
4705 Fio defaults to logging every individual I/O but when windowed logging is set
4706 through :option:`log_avg_msec`, either the average (by default) or the maximum
4707 (:option:`log_max_value` is set) *value* seen over the specified period of time
4708 is recorded. Each *data direction* seen within the window period will aggregate
4709 its values in a separate row. Further, when using windowed logging the *block
4710 size* and *offset* entries will always contain 0.
4716 Normally fio is invoked as a stand-alone application on the machine where the
4717 I/O workload should be generated. However, the backend and frontend of fio can
4718 be run separately i.e., the fio server can generate an I/O workload on the "Device
4719 Under Test" while being controlled by a client on another machine.
4721 Start the server on the machine which has access to the storage DUT::
4725 where `args` defines what fio listens to. The arguments are of the form
4726 ``type,hostname`` or ``IP,port``. *type* is either ``ip`` (or ip4) for TCP/IP
4727 v4, ``ip6`` for TCP/IP v6, or ``sock`` for a local unix domain socket.
4728 *hostname* is either a hostname or IP address, and *port* is the port to listen
4729 to (only valid for TCP/IP, not a local socket). Some examples:
4733 Start a fio server, listening on all interfaces on the default port (8765).
4735 2) ``fio --server=ip:hostname,4444``
4737 Start a fio server, listening on IP belonging to hostname and on port 4444.
4739 3) ``fio --server=ip6:::1,4444``
4741 Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
4743 4) ``fio --server=,4444``
4745 Start a fio server, listening on all interfaces on port 4444.
4747 5) ``fio --server=1.2.3.4``
4749 Start a fio server, listening on IP 1.2.3.4 on the default port.
4751 6) ``fio --server=sock:/tmp/fio.sock``
4753 Start a fio server, listening on the local socket :file:`/tmp/fio.sock`.
4755 Once a server is running, a "client" can connect to the fio server with::
4757 fio <local-args> --client=<server> <remote-args> <job file(s)>
4759 where `local-args` are arguments for the client where it is running, `server`
4760 is the connect string, and `remote-args` and `job file(s)` are sent to the
4761 server. The `server` string follows the same format as it does on the server
4762 side, to allow IP/hostname/socket and port strings.
4764 Fio can connect to multiple servers this way::
4766 fio --client=<server1> <job file(s)> --client=<server2> <job file(s)>
4768 If the job file is located on the fio server, then you can tell the server to
4769 load a local file as well. This is done by using :option:`--remote-config` ::
4771 fio --client=server --remote-config /path/to/file.fio
4773 Then fio will open this local (to the server) job file instead of being passed
4774 one from the client.
4776 If you have many servers (example: 100 VMs/containers), you can input a pathname
4777 of a file containing host IPs/names as the parameter value for the
4778 :option:`--client` option. For example, here is an example :file:`host.list`
4779 file containing 2 hostnames::
4781 host1.your.dns.domain
4782 host2.your.dns.domain
4784 The fio command would then be::
4786 fio --client=host.list <job file(s)>
4788 In this mode, you cannot input server-specific parameters or job files -- all
4789 servers receive the same job file.
4791 In order to let ``fio --client`` runs use a shared filesystem from multiple
4792 hosts, ``fio --client`` now prepends the IP address of the server to the
4793 filename. For example, if fio is using the directory :file:`/mnt/nfs/fio` and is
4794 writing filename :file:`fileio.tmp`, with a :option:`--client` `hostfile`
4795 containing two hostnames ``h1`` and ``h2`` with IP addresses 192.168.10.120 and
4796 192.168.10.121, then fio will create two files::
4798 /mnt/nfs/fio/192.168.10.120.fileio.tmp
4799 /mnt/nfs/fio/192.168.10.121.fileio.tmp
4801 Terse output in client/server mode will differ slightly from what is produced
4802 when fio is run in stand-alone mode. See the terse output section for details.