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 Show available debug options.
99 .. option:: --parse-only
101 Parse options only, don't start any I/O.
103 .. option:: --output=filename
105 Write output to file `filename`.
107 .. option:: --output-format=format
109 Set the reporting `format` to `normal`, `terse`, `json`, or `json+`. Multiple
110 formats can be selected, separated by a comma. `terse` is a CSV based
111 format. `json+` is like `json`, except it adds a full dump of the latency
114 .. option:: --bandwidth-log
116 Generate aggregate bandwidth logs.
118 .. option:: --minimal
120 Print statistics in a terse, semicolon-delimited format.
122 .. option:: --append-terse
124 Print statistics in selected mode AND terse, semicolon-delimited format.
125 **Deprecated**, use :option:`--output-format` instead to select multiple
128 .. option:: --terse-version=version
130 Set terse `version` output format (default 3, or 2 or 4 or 5).
132 .. option:: --version
134 Print version information and exit.
138 Print a summary of the command line options and exit.
140 .. option:: --cpuclock-test
142 Perform test and validation of internal CPU clock.
144 .. option:: --crctest=[test]
146 Test the speed of the built-in checksumming functions. If no argument is
147 given, all of them are tested. Alternatively, a comma separated list can
148 be passed, in which case the given ones are tested.
150 .. option:: --cmdhelp=command
152 Print help information for `command`. May be ``all`` for all commands.
154 .. option:: --enghelp=[ioengine[,command]]
156 List all commands defined by `ioengine`, or print help for `command`
157 defined by `ioengine`. If no `ioengine` is given, list all
160 .. option:: --showcmd=jobfile
162 Convert `jobfile` to a set of command-line options.
164 .. option:: --readonly
166 Turn on safety read-only checks, preventing writes and trims. The
167 ``--readonly`` option is an extra safety guard to prevent users from
168 accidentally starting a write or trim workload when that is not desired.
169 Fio will only modify the device under test if
170 `rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite` is given. This
171 safety net can be used as an extra precaution.
173 .. option:: --eta=when
175 Specifies when real-time ETA estimate should be printed. `when` may be
176 `always`, `never` or `auto`. `auto` is the default, it prints ETA
177 when requested if the output is a TTY. `always` disregards the output
178 type, and prints ETA when requested. `never` never prints ETA.
180 .. option:: --eta-interval=time
182 By default, fio requests client ETA status roughly every second. With
183 this option, the interval is configurable. Fio imposes a minimum
184 allowed time to avoid flooding the console, less than 250 msec is
187 .. option:: --eta-newline=time
189 Force a new line for every `time` period passed. When the unit is omitted,
190 the value is interpreted in seconds.
192 .. option:: --status-interval=time
194 Force a full status dump of cumulative (from job start) values at `time`
195 intervals. This option does *not* provide per-period measurements. So
196 values such as bandwidth are running averages. When the time unit is omitted,
197 `time` is interpreted in seconds.
199 .. option:: --section=name
201 Only run specified section `name` in job file. Multiple sections can be specified.
202 The ``--section`` option allows one to combine related jobs into one file.
203 E.g. one job file could define light, moderate, and heavy sections. Tell
204 fio to run only the "heavy" section by giving ``--section=heavy``
205 command line option. One can also specify the "write" operations in one
206 section and "verify" operation in another section. The ``--section`` option
207 only applies to job sections. The reserved *global* section is always
210 .. option:: --alloc-size=kb
212 Set the internal smalloc pool size to `kb` in KiB. The
213 ``--alloc-size`` switch allows one to use a larger pool size for smalloc.
214 If running large jobs with randommap enabled, fio can run out of memory.
215 Smalloc is an internal allocator for shared structures from a fixed size
216 memory pool and can grow to 16 pools. The pool size defaults to 16MiB.
218 NOTE: While running :file:`.fio_smalloc.*` backing store files are visible
221 .. option:: --warnings-fatal
223 All fio parser warnings are fatal, causing fio to exit with an
226 .. option:: --max-jobs=nr
228 Set the maximum number of threads/processes to support to `nr`.
229 NOTE: On Linux, it may be necessary to increase the shared-memory
230 limit (:file:`/proc/sys/kernel/shmmax`) if fio runs into errors while
233 .. option:: --server=args
235 Start a backend server, with `args` specifying what to listen to.
236 See `Client/Server`_ section.
238 .. option:: --daemonize=pidfile
240 Background a fio server, writing the pid to the given `pidfile` file.
242 .. option:: --client=hostname
244 Instead of running the jobs locally, send and run them on the given `hostname`
245 or set of `hostname`\s. See `Client/Server`_ section.
247 .. option:: --remote-config=file
249 Tell fio server to load this local `file`.
251 .. option:: --idle-prof=option
253 Report CPU idleness. `option` is one of the following:
256 Run unit work calibration only and exit.
259 Show aggregate system idleness and unit work.
262 As **system** but also show per CPU idleness.
264 .. option:: --inflate-log=log
266 Inflate and output compressed `log`.
268 .. option:: --trigger-file=file
270 Execute trigger command when `file` exists.
272 .. option:: --trigger-timeout=time
274 Execute trigger at this `time`.
276 .. option:: --trigger=command
278 Set this `command` as local trigger.
280 .. option:: --trigger-remote=command
282 Set this `command` as remote trigger.
284 .. option:: --aux-path=path
286 Use the directory specified by `path` for generated state files instead
287 of the current working directory.
289 Any parameters following the options will be assumed to be job files, unless
290 they match a job file parameter. Multiple job files can be listed and each job
291 file will be regarded as a separate group. Fio will :option:`stonewall`
292 execution between each group.
298 As previously described, fio accepts one or more job files describing what it is
299 supposed to do. The job file format is the classic ini file, where the names
300 enclosed in [] brackets define the job name. You are free to use any ASCII name
301 you want, except *global* which has special meaning. Following the job name is
302 a sequence of zero or more parameters, one per line, that define the behavior of
303 the job. If the first character in a line is a ';' or a '#', the entire line is
304 discarded as a comment.
306 A *global* section sets defaults for the jobs described in that file. A job may
307 override a *global* section parameter, and a job file may even have several
308 *global* sections if so desired. A job is only affected by a *global* section
311 The :option:`--cmdhelp` option also lists all options. If used with a `command`
312 argument, :option:`--cmdhelp` will detail the given `command`.
314 See the `examples/` directory for inspiration on how to write job files. Note
315 the copyright and license requirements currently apply to `examples/` files.
317 So let's look at a really simple job file that defines two processes, each
318 randomly reading from a 128MiB file:
322 ; -- start job file --
333 As you can see, the job file sections themselves are empty as all the described
334 parameters are shared. As no :option:`filename` option is given, fio makes up a
335 `filename` for each of the jobs as it sees fit. On the command line, this job
336 would look as follows::
338 $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
341 Let's look at an example that has a number of processes writing randomly to
346 ; -- start job file --
357 Here we have no *global* section, as we only have one job defined anyway. We
358 want to use async I/O here, with a depth of 4 for each file. We also increased
359 the buffer size used to 32KiB and define numjobs to 4 to fork 4 identical
360 jobs. The result is 4 processes each randomly writing to their own 64MiB
361 file. Instead of using the above job file, you could have given the parameters
362 on the command line. For this case, you would specify::
364 $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
366 When fio is utilized as a basis of any reasonably large test suite, it might be
367 desirable to share a set of standardized settings across multiple job files.
368 Instead of copy/pasting such settings, any section may pull in an external
369 :file:`filename.fio` file with *include filename* directive, as in the following
372 ; -- start job file including.fio --
376 include glob-include.fio
383 include test-include.fio
384 ; -- end job file including.fio --
388 ; -- start job file glob-include.fio --
391 ; -- end job file glob-include.fio --
395 ; -- start job file test-include.fio --
398 ; -- end job file test-include.fio --
400 Settings pulled into a section apply to that section only (except *global*
401 section). Include directives may be nested in that any included file may contain
402 further include directive(s). Include files may not contain [] sections.
405 Environment variables
406 ~~~~~~~~~~~~~~~~~~~~~
408 Fio also supports environment variable expansion in job files. Any sub-string of
409 the form ``${VARNAME}`` as part of an option value (in other words, on the right
410 of the '='), will be expanded to the value of the environment variable called
411 `VARNAME`. If no such environment variable is defined, or `VARNAME` is the
412 empty string, the empty string will be substituted.
414 As an example, let's look at a sample fio invocation and job file::
416 $ SIZE=64m NUMJOBS=4 fio jobfile.fio
420 ; -- start job file --
427 This will expand to the following equivalent job file at runtime:
431 ; -- start job file --
438 Fio ships with a few example job files, you can also look there for inspiration.
443 Additionally, fio has a set of reserved keywords that will be replaced
444 internally with the appropriate value. Those keywords are:
448 The architecture page size of the running system.
452 Megabytes of total memory in the system.
456 Number of online available CPUs.
458 These can be used on the command line or in the job file, and will be
459 automatically substituted with the current system values when the job is
460 run. Simple math is also supported on these keywords, so you can perform actions
465 and get that properly expanded to 8 times the size of memory in the machine.
471 This section describes in details each parameter associated with a job. Some
472 parameters take an option of a given type, such as an integer or a
473 string. Anywhere a numeric value is required, an arithmetic expression may be
474 used, provided it is surrounded by parentheses. Supported operators are:
483 For time values in expressions, units are microseconds by default. This is
484 different than for time values not in expressions (not enclosed in
485 parentheses). The following types are used:
492 String: A sequence of alphanumeric characters.
495 Integer with possible time suffix. Without a unit value is interpreted as
496 seconds unless otherwise specified. Accepts a suffix of 'd' for days, 'h' for
497 hours, 'm' for minutes, 's' for seconds, 'ms' (or 'msec') for milliseconds and
498 'us' (or 'usec') for microseconds. For example, use 10m for 10 minutes.
503 Integer. A whole number value, which may contain an integer prefix
504 and an integer suffix:
506 [*integer prefix*] **number** [*integer suffix*]
508 The optional *integer prefix* specifies the number's base. The default
509 is decimal. *0x* specifies hexadecimal.
511 The optional *integer suffix* specifies the number's units, and includes an
512 optional unit prefix and an optional unit. For quantities of data, the
513 default unit is bytes. For quantities of time, the default unit is seconds
514 unless otherwise specified.
516 With :option:`kb_base`\=1000, fio follows international standards for unit
517 prefixes. To specify power-of-10 decimal values defined in the
518 International System of Units (SI):
520 * *K* -- means kilo (K) or 1000
521 * *M* -- means mega (M) or 1000**2
522 * *G* -- means giga (G) or 1000**3
523 * *T* -- means tera (T) or 1000**4
524 * *P* -- means peta (P) or 1000**5
526 To specify power-of-2 binary values defined in IEC 80000-13:
528 * *Ki* -- means kibi (Ki) or 1024
529 * *Mi* -- means mebi (Mi) or 1024**2
530 * *Gi* -- means gibi (Gi) or 1024**3
531 * *Ti* -- means tebi (Ti) or 1024**4
532 * *Pi* -- means pebi (Pi) or 1024**5
534 With :option:`kb_base`\=1024 (the default), the unit prefixes are opposite
535 from those specified in the SI and IEC 80000-13 standards to provide
536 compatibility with old scripts. For example, 4k means 4096.
538 For quantities of data, an optional unit of 'B' may be included
539 (e.g., 'kB' is the same as 'k').
541 The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega,
542 not milli). 'b' and 'B' both mean byte, not bit.
544 Examples with :option:`kb_base`\=1000:
546 * *4 KiB*: 4096, 4096b, 4096B, 4ki, 4kib, 4kiB, 4Ki, 4KiB
547 * *1 MiB*: 1048576, 1mi, 1024ki
548 * *1 MB*: 1000000, 1m, 1000k
549 * *1 TiB*: 1099511627776, 1ti, 1024gi, 1048576mi
550 * *1 TB*: 1000000000, 1t, 1000m, 1000000k
552 Examples with :option:`kb_base`\=1024 (default):
554 * *4 KiB*: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
555 * *1 MiB*: 1048576, 1m, 1024k
556 * *1 MB*: 1000000, 1mi, 1000ki
557 * *1 TiB*: 1099511627776, 1t, 1024g, 1048576m
558 * *1 TB*: 1000000000, 1ti, 1000mi, 1000000ki
560 To specify times (units are not case sensitive):
564 * *M* -- means minutes
565 * *s* -- or sec means seconds (default)
566 * *ms* -- or *msec* means milliseconds
567 * *us* -- or *usec* means microseconds
569 If the option accepts an upper and lower range, use a colon ':' or
570 minus '-' to separate such values. See :ref:`irange <irange>`.
571 If the lower value specified happens to be larger than the upper value
572 the two values are swapped.
577 Boolean. Usually parsed as an integer, however only defined for
578 true and false (1 and 0).
583 Integer range with suffix. Allows value range to be given, such as
584 1024-4096. A colon may also be used as the separator, e.g. 1k:4k. If the
585 option allows two sets of ranges, they can be specified with a ',' or '/'
586 delimiter: 1k-4k/8k-32k. Also see :ref:`int <int>`.
589 A list of floating point numbers, separated by a ':' character.
591 With the above in mind, here follows the complete list of fio job parameters.
597 .. option:: kb_base=int
599 Select the interpretation of unit prefixes in input parameters.
602 Inputs comply with IEC 80000-13 and the International
603 System of Units (SI). Use:
605 - power-of-2 values with IEC prefixes (e.g., KiB)
606 - power-of-10 values with SI prefixes (e.g., kB)
609 Compatibility mode (default). To avoid breaking old scripts:
611 - power-of-2 values with SI prefixes
612 - power-of-10 values with IEC prefixes
614 See :option:`bs` for more details on input parameters.
616 Outputs always use correct prefixes. Most outputs include both
619 bw=2383.3kB/s (2327.4KiB/s)
621 If only one value is reported, then kb_base selects the one to use:
623 **1000** -- SI prefixes
625 **1024** -- IEC prefixes
627 .. option:: unit_base=int
629 Base unit for reporting. Allowed values are:
632 Use auto-detection (default).
644 ASCII name of the job. This may be used to override the name printed by fio
645 for this job. Otherwise the job name is used. On the command line this
646 parameter has the special purpose of also signaling the start of a new job.
648 .. option:: description=str
650 Text description of the job. Doesn't do anything except dump this text
651 description when this job is run. It's not parsed.
653 .. option:: loops=int
655 Run the specified number of iterations of this job. Used to repeat the same
656 workload a given number of times. Defaults to 1.
658 .. option:: numjobs=int
660 Create the specified number of clones of this job. Each clone of job
661 is spawned as an independent thread or process. May be used to setup a
662 larger number of threads/processes doing the same thing. Each thread is
663 reported separately; to see statistics for all clones as a whole, use
664 :option:`group_reporting` in conjunction with :option:`new_group`.
665 See :option:`--max-jobs`. Default: 1.
668 Time related parameters
669 ~~~~~~~~~~~~~~~~~~~~~~~
671 .. option:: runtime=time
673 Tell fio to terminate processing after the specified period of time. It
674 can be quite hard to determine for how long a specified job will run, so
675 this parameter is handy to cap the total runtime to a given time. When
676 the unit is omitted, the value is interpreted in seconds.
678 .. option:: time_based
680 If set, fio will run for the duration of the :option:`runtime` specified
681 even if the file(s) are completely read or written. It will simply loop over
682 the same workload as many times as the :option:`runtime` allows.
684 .. option:: startdelay=irange(time)
686 Delay the start of job for the specified amount of time. Can be a single
687 value or a range. When given as a range, each thread will choose a value
688 randomly from within the range. Value is in seconds if a unit is omitted.
690 .. option:: ramp_time=time
692 If set, fio will run the specified workload for this amount of time before
693 logging any performance numbers. Useful for letting performance settle
694 before logging results, thus minimizing the runtime required for stable
695 results. Note that the ``ramp_time`` is considered lead in time for a job,
696 thus it will increase the total runtime if a special timeout or
697 :option:`runtime` is specified. When the unit is omitted, the value is
700 .. option:: clocksource=str
702 Use the given clocksource as the base of timing. The supported options are:
705 :manpage:`gettimeofday(2)`
708 :manpage:`clock_gettime(2)`
711 Internal CPU clock source
713 cpu is the preferred clocksource if it is reliable, as it is very fast (and
714 fio is heavy on time calls). Fio will automatically use this clocksource if
715 it's supported and considered reliable on the system it is running on,
716 unless another clocksource is specifically set. For x86/x86-64 CPUs, this
717 means supporting TSC Invariant.
719 .. option:: gtod_reduce=bool
721 Enable all of the :manpage:`gettimeofday(2)` reducing options
722 (:option:`disable_clat`, :option:`disable_slat`, :option:`disable_bw_measurement`) plus
723 reduce precision of the timeout somewhat to really shrink the
724 :manpage:`gettimeofday(2)` call count. With this option enabled, we only do
725 about 0.4% of the :manpage:`gettimeofday(2)` calls we would have done if all
726 time keeping was enabled.
728 .. option:: gtod_cpu=int
730 Sometimes it's cheaper to dedicate a single thread of execution to just
731 getting the current time. Fio (and databases, for instance) are very
732 intensive on :manpage:`gettimeofday(2)` calls. With this option, you can set
733 one CPU aside for doing nothing but logging current time to a shared memory
734 location. Then the other threads/processes that run I/O workloads need only
735 copy that segment, instead of entering the kernel with a
736 :manpage:`gettimeofday(2)` call. The CPU set aside for doing these time
737 calls will be excluded from other uses. Fio will manually clear it from the
738 CPU mask of other jobs.
744 .. option:: directory=str
746 Prefix filenames with this directory. Used to place files in a different
747 location than :file:`./`. You can specify a number of directories by
748 separating the names with a ':' character. These directories will be
749 assigned equally distributed to job clones created by :option:`numjobs` as
750 long as they are using generated filenames. If specific `filename(s)` are
751 set fio will use the first listed directory, and thereby matching the
752 `filename` semantic (which generates a file for each clone if not
753 specified, but lets all clones use the same file if set).
755 See the :option:`filename` option for information on how to escape "``:``" and
756 "``\``" characters within the directory path itself.
758 Note: To control the directory fio will use for internal state files
759 use :option:`--aux-path`.
761 .. option:: filename=str
763 Fio normally makes up a `filename` based on the job name, thread number, and
764 file number (see :option:`filename_format`). If you want to share files
765 between threads in a job or several
766 jobs with fixed file paths, specify a `filename` for each of them to override
767 the default. If the ioengine is file based, you can specify a number of files
768 by separating the names with a ':' colon. So if you wanted a job to open
769 :file:`/dev/sda` and :file:`/dev/sdb` as the two working files, you would use
770 ``filename=/dev/sda:/dev/sdb``. This also means that whenever this option is
771 specified, :option:`nrfiles` is ignored. The size of regular files specified
772 by this option will be :option:`size` divided by number of files unless an
773 explicit size is specified by :option:`filesize`.
775 Each colon and backslash in the wanted path must be escaped with a ``\``
776 character. For instance, if the path is :file:`/dev/dsk/foo@3,0:c` then you
777 would use ``filename=/dev/dsk/foo@3,0\:c`` and if the path is
778 :file:`F:\\filename` then you would use ``filename=F\:\\filename``.
780 On Windows, disk devices are accessed as :file:`\\\\.\\PhysicalDrive0` for
781 the first device, :file:`\\\\.\\PhysicalDrive1` for the second etc.
782 Note: Windows and FreeBSD prevent write access to areas
783 of the disk containing in-use data (e.g. filesystems).
785 The filename "`-`" is a reserved name, meaning *stdin* or *stdout*. Which
786 of the two depends on the read/write direction set.
788 .. option:: filename_format=str
790 If sharing multiple files between jobs, it is usually necessary to have fio
791 generate the exact names that you want. By default, fio will name a file
792 based on the default file format specification of
793 :file:`jobname.jobnumber.filenumber`. With this option, that can be
794 customized. Fio will recognize and replace the following keywords in this
798 The name of the worker thread or process.
800 The incremental number of the worker thread or process.
802 The incremental number of the file for that worker thread or
805 To have dependent jobs share a set of files, this option can be set to have
806 fio generate filenames that are shared between the two. For instance, if
807 :file:`testfiles.$filenum` is specified, file number 4 for any job will be
808 named :file:`testfiles.4`. The default of :file:`$jobname.$jobnum.$filenum`
809 will be used if no other format specifier is given.
811 If you specify a path then the directories will be created up to the
812 main directory for the file. So for example if you specify
813 ``filename_format=a/b/c/$jobnum`` then the directories a/b/c will be
814 created before the file setup part of the job. If you specify
815 :option:`directory` then the path will be relative that directory,
816 otherwise it is treated as the absolute path.
818 .. option:: unique_filename=bool
820 To avoid collisions between networked clients, fio defaults to prefixing any
821 generated filenames (with a directory specified) with the source of the
822 client connecting. To disable this behavior, set this option to 0.
824 .. option:: opendir=str
826 Recursively open any files below directory `str`.
828 .. option:: lockfile=str
830 Fio defaults to not locking any files before it does I/O to them. If a file
831 or file descriptor is shared, fio can serialize I/O to that file to make the
832 end result consistent. This is usual for emulating real workloads that share
833 files. The lock modes are:
836 No locking. The default.
838 Only one thread or process may do I/O at a time, excluding all
841 Read-write locking on the file. Many readers may
842 access the file at the same time, but writes get exclusive access.
844 .. option:: nrfiles=int
846 Number of files to use for this job. Defaults to 1. The size of files
847 will be :option:`size` divided by this unless explicit size is specified by
848 :option:`filesize`. Files are created for each thread separately, and each
849 file will have a file number within its name by default, as explained in
850 :option:`filename` section.
853 .. option:: openfiles=int
855 Number of files to keep open at the same time. Defaults to the same as
856 :option:`nrfiles`, can be set smaller to limit the number simultaneous
859 .. option:: file_service_type=str
861 Defines how fio decides which file from a job to service next. The following
865 Choose a file at random.
868 Round robin over opened files. This is the default.
871 Finish one file before moving on to the next. Multiple files can
872 still be open depending on :option:`openfiles`.
875 Use a *Zipf* distribution to decide what file to access.
878 Use a *Pareto* distribution to decide what file to access.
881 Use a *Gaussian* (normal) distribution to decide what file to
887 For *random*, *roundrobin*, and *sequential*, a postfix can be appended to
888 tell fio how many I/Os to issue before switching to a new file. For example,
889 specifying ``file_service_type=random:8`` would cause fio to issue
890 8 I/Os before selecting a new file at random. For the non-uniform
891 distributions, a floating point postfix can be given to influence how the
892 distribution is skewed. See :option:`random_distribution` for a description
893 of how that would work.
895 .. option:: ioscheduler=str
897 Attempt to switch the device hosting the file to the specified I/O scheduler
900 .. option:: create_serialize=bool
902 If true, serialize the file creation for the jobs. This may be handy to
903 avoid interleaving of data files, which may greatly depend on the filesystem
904 used and even the number of processors in the system. Default: true.
906 .. option:: create_fsync=bool
908 :manpage:`fsync(2)` the data file after creation. This is the default.
910 .. option:: create_on_open=bool
912 If true, don't pre-create files but allow the job's open() to create a file
913 when it's time to do I/O. Default: false -- pre-create all necessary files
916 .. option:: create_only=bool
918 If true, fio will only run the setup phase of the job. If files need to be
919 laid out or updated on disk, only that will be done -- the actual job contents
920 are not executed. Default: false.
922 .. option:: allow_file_create=bool
924 If true, fio is permitted to create files as part of its workload. If this
925 option is false, then fio will error out if
926 the files it needs to use don't already exist. Default: true.
928 .. option:: allow_mounted_write=bool
930 If this isn't set, fio will abort jobs that are destructive (e.g. that write)
931 to what appears to be a mounted device or partition. This should help catch
932 creating inadvertently destructive tests, not realizing that the test will
933 destroy data on the mounted file system. Note that some platforms don't allow
934 writing against a mounted device regardless of this option. Default: false.
936 .. option:: pre_read=bool
938 If this is given, files will be pre-read into memory before starting the
939 given I/O operation. This will also clear the :option:`invalidate` flag,
940 since it is pointless to pre-read and then drop the cache. This will only
941 work for I/O engines that are seek-able, since they allow you to read the
942 same data multiple times. Thus it will not work on non-seekable I/O engines
943 (e.g. network, splice). Default: false.
945 .. option:: unlink=bool
947 Unlink the job files when done. Not the default, as repeated runs of that
948 job would then waste time recreating the file set again and again. Default:
951 .. option:: unlink_each_loop=bool
953 Unlink job files after each iteration or loop. Default: false.
955 .. option:: zonemode=str
960 The :option:`zonerange`, :option:`zonesize` and
961 :option:`zoneskip` parameters are ignored.
963 I/O happens in a single zone until
964 :option:`zonesize` bytes have been transferred.
965 After that number of bytes has been
966 transferred processing of the next zone
969 Zoned block device mode. I/O happens
970 sequentially in each zone, even if random I/O
971 has been selected. Random I/O happens across
972 all zones instead of being restricted to a
973 single zone. The :option:`zoneskip` parameter
974 is ignored. :option:`zonerange` and
975 :option:`zonesize` must be identical.
977 .. option:: zonerange=int
979 Size of a single zone. See also :option:`zonesize` and
982 .. option:: zonesize=int
984 For :option:`zonemode` =strided, this is the number of bytes to
985 transfer before skipping :option:`zoneskip` bytes. If this parameter
986 is smaller than :option:`zonerange` then only a fraction of each zone
987 with :option:`zonerange` bytes will be accessed. If this parameter is
988 larger than :option:`zonerange` then each zone will be accessed
989 multiple times before skipping to the next zone.
991 For :option:`zonemode` =zbd, this is the size of a single zone. The
992 :option:`zonerange` parameter is ignored in this mode.
994 .. option:: zoneskip=int
996 For :option:`zonemode` =strided, the number of bytes to skip after
997 :option:`zonesize` bytes of data have been transferred. This parameter
998 must be zero for :option:`zonemode` =zbd.
1000 .. option:: read_beyond_wp=bool
1002 This parameter applies to :option:`zonemode` =zbd only.
1004 Zoned block devices are block devices that consist of multiple zones.
1005 Each zone has a type, e.g. conventional or sequential. A conventional
1006 zone can be written at any offset that is a multiple of the block
1007 size. Sequential zones must be written sequentially. The position at
1008 which a write must occur is called the write pointer. A zoned block
1009 device can be either drive managed, host managed or host aware. For
1010 host managed devices the host must ensure that writes happen
1011 sequentially. Fio recognizes host managed devices and serializes
1012 writes to sequential zones for these devices.
1014 If a read occurs in a sequential zone beyond the write pointer then
1015 the zoned block device will complete the read without reading any data
1016 from the storage medium. Since such reads lead to unrealistically high
1017 bandwidth and IOPS numbers fio only reads beyond the write pointer if
1018 explicitly told to do so. Default: false.
1024 .. option:: direct=bool
1026 If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that
1027 OpenBSD and ZFS on Solaris don't support direct I/O. On Windows the synchronous
1028 ioengines don't support direct I/O. Default: false.
1030 .. option:: atomic=bool
1032 If value is true, attempt to use atomic direct I/O. Atomic writes are
1033 guaranteed to be stable once acknowledged by the operating system. Only
1034 Linux supports O_ATOMIC right now.
1036 .. option:: buffered=bool
1038 If value is true, use buffered I/O. This is the opposite of the
1039 :option:`direct` option. Defaults to true.
1041 .. option:: readwrite=str, rw=str
1043 Type of I/O pattern. Accepted values are:
1050 Sequential trims (Linux block devices and SCSI
1051 character devices only).
1057 Random trims (Linux block devices and SCSI
1058 character devices only).
1060 Sequential mixed reads and writes.
1062 Random mixed reads and writes.
1064 Sequential trim+write sequences. Blocks will be trimmed first,
1065 then the same blocks will be written to.
1067 Fio defaults to read if the option is not specified. For the mixed I/O
1068 types, the default is to split them 50/50. For certain types of I/O the
1069 result may still be skewed a bit, since the speed may be different.
1071 It is possible to specify the number of I/Os to do before getting a new
1072 offset by appending ``:<nr>`` to the end of the string given. For a
1073 random read, it would look like ``rw=randread:8`` for passing in an offset
1074 modifier with a value of 8. If the suffix is used with a sequential I/O
1075 pattern, then the *<nr>* value specified will be **added** to the generated
1076 offset for each I/O turning sequential I/O into sequential I/O with holes.
1077 For instance, using ``rw=write:4k`` will skip 4k for every write. Also see
1078 the :option:`rw_sequencer` option.
1080 .. option:: rw_sequencer=str
1082 If an offset modifier is given by appending a number to the ``rw=<str>``
1083 line, then this option controls how that number modifies the I/O offset
1084 being generated. Accepted values are:
1087 Generate sequential offset.
1089 Generate the same offset.
1091 ``sequential`` is only useful for random I/O, where fio would normally
1092 generate a new random offset for every I/O. If you append e.g. 8 to randread,
1093 you would get a new random offset for every 8 I/Os. The result would be a
1094 seek for only every 8 I/Os, instead of for every I/O. Use ``rw=randread:8``
1095 to specify that. As sequential I/O is already sequential, setting
1096 ``sequential`` for that would not result in any differences. ``identical``
1097 behaves in a similar fashion, except it sends the same offset 8 number of
1098 times before generating a new offset.
1100 .. option:: unified_rw_reporting=bool
1102 Fio normally reports statistics on a per data direction basis, meaning that
1103 reads, writes, and trims are accounted and reported separately. If this
1104 option is set fio sums the results and report them as "mixed" instead.
1106 .. option:: randrepeat=bool
1108 Seed the random number generator used for random I/O patterns in a
1109 predictable way so the pattern is repeatable across runs. Default: true.
1111 .. option:: allrandrepeat=bool
1113 Seed all random number generators in a predictable way so results are
1114 repeatable across runs. Default: false.
1116 .. option:: randseed=int
1118 Seed the random number generators based on this seed value, to be able to
1119 control what sequence of output is being generated. If not set, the random
1120 sequence depends on the :option:`randrepeat` setting.
1122 .. option:: fallocate=str
1124 Whether pre-allocation is performed when laying down files.
1125 Accepted values are:
1128 Do not pre-allocate space.
1131 Use a platform's native pre-allocation call but fall back to
1132 **none** behavior if it fails/is not implemented.
1135 Pre-allocate via :manpage:`posix_fallocate(3)`.
1138 Pre-allocate via :manpage:`fallocate(2)` with
1139 FALLOC_FL_KEEP_SIZE set.
1142 Backward-compatible alias for **none**.
1145 Backward-compatible alias for **posix**.
1147 May not be available on all supported platforms. **keep** is only available
1148 on Linux. If using ZFS on Solaris this cannot be set to **posix**
1149 because ZFS doesn't support pre-allocation. Default: **native** if any
1150 pre-allocation methods are available, **none** if not.
1152 .. option:: fadvise_hint=str
1154 Use :manpage:`posix_fadvise(2)` or :manpage:`posix_fadvise(2)` to
1155 advise the kernel on what I/O patterns are likely to be issued.
1156 Accepted values are:
1159 Backwards-compatible hint for "no hint".
1162 Backwards compatible hint for "advise with fio workload type". This
1163 uses **FADV_RANDOM** for a random workload, and **FADV_SEQUENTIAL**
1164 for a sequential workload.
1167 Advise using **FADV_SEQUENTIAL**.
1170 Advise using **FADV_RANDOM**.
1172 .. option:: write_hint=str
1174 Use :manpage:`fcntl(2)` to advise the kernel what life time to expect
1175 from a write. Only supported on Linux, as of version 4.13. Accepted
1179 No particular life time associated with this file.
1182 Data written to this file has a short life time.
1185 Data written to this file has a medium life time.
1188 Data written to this file has a long life time.
1191 Data written to this file has a very long life time.
1193 The values are all relative to each other, and no absolute meaning
1194 should be associated with them.
1196 .. option:: offset=int
1198 Start I/O at the provided offset in the file, given as either a fixed size in
1199 bytes or a percentage. If a percentage is given, the generated offset will be
1200 aligned to the minimum ``blocksize`` or to the value of ``offset_align`` if
1201 provided. Data before the given offset will not be touched. This
1202 effectively caps the file size at `real_size - offset`. Can be combined with
1203 :option:`size` to constrain the start and end range of the I/O workload.
1204 A percentage can be specified by a number between 1 and 100 followed by '%',
1205 for example, ``offset=20%`` to specify 20%.
1207 .. option:: offset_align=int
1209 If set to non-zero value, the byte offset generated by a percentage ``offset``
1210 is aligned upwards to this value. Defaults to 0 meaning that a percentage
1211 offset is aligned to the minimum block size.
1213 .. option:: offset_increment=int
1215 If this is provided, then the real offset becomes `offset + offset_increment
1216 * thread_number`, where the thread number is a counter that starts at 0 and
1217 is incremented for each sub-job (i.e. when :option:`numjobs` option is
1218 specified). This option is useful if there are several jobs which are
1219 intended to operate on a file in parallel disjoint segments, with even
1220 spacing between the starting points.
1222 .. option:: number_ios=int
1224 Fio will normally perform I/Os until it has exhausted the size of the region
1225 set by :option:`size`, or if it exhaust the allocated time (or hits an error
1226 condition). With this setting, the range/size can be set independently of
1227 the number of I/Os to perform. When fio reaches this number, it will exit
1228 normally and report status. Note that this does not extend the amount of I/O
1229 that will be done, it will only stop fio if this condition is met before
1230 other end-of-job criteria.
1232 .. option:: fsync=int
1234 If writing to a file, issue an :manpage:`fsync(2)` (or its equivalent) of
1235 the dirty data for every number of blocks given. For example, if you give 32
1236 as a parameter, fio will sync the file after every 32 writes issued. If fio is
1237 using non-buffered I/O, we may not sync the file. The exception is the sg
1238 I/O engine, which synchronizes the disk cache anyway. Defaults to 0, which
1239 means fio does not periodically issue and wait for a sync to complete. Also
1240 see :option:`end_fsync` and :option:`fsync_on_close`.
1242 .. option:: fdatasync=int
1244 Like :option:`fsync` but uses :manpage:`fdatasync(2)` to only sync data and
1245 not metadata blocks. In Windows, FreeBSD, and DragonFlyBSD there is no
1246 :manpage:`fdatasync(2)` so this falls back to using :manpage:`fsync(2)`.
1247 Defaults to 0, which means fio does not periodically issue and wait for a
1248 data-only sync to complete.
1250 .. option:: write_barrier=int
1252 Make every `N-th` write a barrier write.
1254 .. option:: sync_file_range=str:int
1256 Use :manpage:`sync_file_range(2)` for every `int` number of write
1257 operations. Fio will track range of writes that have happened since the last
1258 :manpage:`sync_file_range(2)` call. `str` can currently be one or more of:
1261 SYNC_FILE_RANGE_WAIT_BEFORE
1263 SYNC_FILE_RANGE_WRITE
1265 SYNC_FILE_RANGE_WAIT_AFTER
1267 So if you do ``sync_file_range=wait_before,write:8``, fio would use
1268 ``SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE`` for every 8
1269 writes. Also see the :manpage:`sync_file_range(2)` man page. This option is
1272 .. option:: overwrite=bool
1274 If true, writes to a file will always overwrite existing data. If the file
1275 doesn't already exist, it will be created before the write phase begins. If
1276 the file exists and is large enough for the specified write phase, nothing
1277 will be done. Default: false.
1279 .. option:: end_fsync=bool
1281 If true, :manpage:`fsync(2)` file contents when a write stage has completed.
1284 .. option:: fsync_on_close=bool
1286 If true, fio will :manpage:`fsync(2)` a dirty file on close. This differs
1287 from :option:`end_fsync` in that it will happen on every file close, not
1288 just at the end of the job. Default: false.
1290 .. option:: rwmixread=int
1292 Percentage of a mixed workload that should be reads. Default: 50.
1294 .. option:: rwmixwrite=int
1296 Percentage of a mixed workload that should be writes. If both
1297 :option:`rwmixread` and :option:`rwmixwrite` is given and the values do not
1298 add up to 100%, the latter of the two will be used to override the
1299 first. This may interfere with a given rate setting, if fio is asked to
1300 limit reads or writes to a certain rate. If that is the case, then the
1301 distribution may be skewed. Default: 50.
1303 .. option:: random_distribution=str:float[,str:float][,str:float]
1305 By default, fio will use a completely uniform random distribution when asked
1306 to perform random I/O. Sometimes it is useful to skew the distribution in
1307 specific ways, ensuring that some parts of the data is more hot than others.
1308 fio includes the following distribution models:
1311 Uniform random distribution
1320 Normal (Gaussian) distribution
1323 Zoned random distribution
1326 Zone absolute random distribution
1328 When using a **zipf** or **pareto** distribution, an input value is also
1329 needed to define the access pattern. For **zipf**, this is the `Zipf
1330 theta`. For **pareto**, it's the `Pareto power`. Fio includes a test
1331 program, :command:`fio-genzipf`, that can be used visualize what the given input
1332 values will yield in terms of hit rates. If you wanted to use **zipf** with
1333 a `theta` of 1.2, you would use ``random_distribution=zipf:1.2`` as the
1334 option. If a non-uniform model is used, fio will disable use of the random
1335 map. For the **normal** distribution, a normal (Gaussian) deviation is
1336 supplied as a value between 0 and 100.
1338 For a **zoned** distribution, fio supports specifying percentages of I/O
1339 access that should fall within what range of the file or device. For
1340 example, given a criteria of:
1342 * 60% of accesses should be to the first 10%
1343 * 30% of accesses should be to the next 20%
1344 * 8% of accesses should be to the next 30%
1345 * 2% of accesses should be to the next 40%
1347 we can define that through zoning of the random accesses. For the above
1348 example, the user would do::
1350 random_distribution=zoned:60/10:30/20:8/30:2/40
1352 A **zoned_abs** distribution works exactly like the **zoned**, except
1353 that it takes absolute sizes. For example, let's say you wanted to
1354 define access according to the following criteria:
1356 * 60% of accesses should be to the first 20G
1357 * 30% of accesses should be to the next 100G
1358 * 10% of accesses should be to the next 500G
1360 we can define an absolute zoning distribution with:
1362 random_distribution=zoned_abs=60/20G:30/100G:10/500g
1364 For both **zoned** and **zoned_abs**, fio supports defining up to
1367 Similarly to how :option:`bssplit` works for setting ranges and
1368 percentages of block sizes. Like :option:`bssplit`, it's possible to
1369 specify separate zones for reads, writes, and trims. If just one set
1370 is given, it'll apply to all of them. This goes for both **zoned**
1371 **zoned_abs** distributions.
1373 .. option:: percentage_random=int[,int][,int]
1375 For a random workload, set how big a percentage should be random. This
1376 defaults to 100%, in which case the workload is fully random. It can be set
1377 from anywhere from 0 to 100. Setting it to 0 would make the workload fully
1378 sequential. Any setting in between will result in a random mix of sequential
1379 and random I/O, at the given percentages. Comma-separated values may be
1380 specified for reads, writes, and trims as described in :option:`blocksize`.
1382 .. option:: norandommap
1384 Normally fio will cover every block of the file when doing random I/O. If
1385 this option is given, fio will just get a new random offset without looking
1386 at past I/O history. This means that some blocks may not be read or written,
1387 and that some blocks may be read/written more than once. If this option is
1388 used with :option:`verify` and multiple blocksizes (via :option:`bsrange`),
1389 only intact blocks are verified, i.e., partially-overwritten blocks are
1390 ignored. With an async I/O engine and an I/O depth > 1, it is possible for
1391 the same block to be overwritten, which can cause verification errors. Either
1392 do not use norandommap in this case, or also use the lfsr random generator.
1394 .. option:: softrandommap=bool
1396 See :option:`norandommap`. If fio runs with the random block map enabled and
1397 it fails to allocate the map, if this option is set it will continue without
1398 a random block map. As coverage will not be as complete as with random maps,
1399 this option is disabled by default.
1401 .. option:: random_generator=str
1403 Fio supports the following engines for generating I/O offsets for random I/O:
1406 Strong 2^88 cycle random number generator.
1408 Linear feedback shift register generator.
1410 Strong 64-bit 2^258 cycle random number generator.
1412 **tausworthe** is a strong random number generator, but it requires tracking
1413 on the side if we want to ensure that blocks are only read or written
1414 once. **lfsr** guarantees that we never generate the same offset twice, and
1415 it's also less computationally expensive. It's not a true random generator,
1416 however, though for I/O purposes it's typically good enough. **lfsr** only
1417 works with single block sizes, not with workloads that use multiple block
1418 sizes. If used with such a workload, fio may read or write some blocks
1419 multiple times. The default value is **tausworthe**, unless the required
1420 space exceeds 2^32 blocks. If it does, then **tausworthe64** is
1421 selected automatically.
1427 .. option:: blocksize=int[,int][,int], bs=int[,int][,int]
1429 The block size in bytes used for I/O units. Default: 4096. A single value
1430 applies to reads, writes, and trims. Comma-separated values may be
1431 specified for reads, writes, and trims. A value not terminated in a comma
1432 applies to subsequent types.
1437 means 256k for reads, writes and trims.
1440 means 8k for reads, 32k for writes and trims.
1443 means 8k for reads, 32k for writes, and default for trims.
1446 means default for reads, 8k for writes and trims.
1449 means default for reads, 8k for writes, and default for trims.
1451 .. option:: blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
1453 A range of block sizes in bytes for I/O units. The issued I/O unit will
1454 always be a multiple of the minimum size, unless
1455 :option:`blocksize_unaligned` is set.
1457 Comma-separated ranges may be specified for reads, writes, and trims as
1458 described in :option:`blocksize`.
1460 Example: ``bsrange=1k-4k,2k-8k``.
1462 .. option:: bssplit=str[,str][,str]
1464 Sometimes you want even finer grained control of the block sizes
1465 issued, not just an even split between them. This option allows you to
1466 weight various block sizes, so that you are able to define a specific
1467 amount of block sizes issued. The format for this option is::
1469 bssplit=blocksize/percentage:blocksize/percentage
1471 for as many block sizes as needed. So if you want to define a workload
1472 that has 50% 64k blocks, 10% 4k blocks, and 40% 32k blocks, you would
1475 bssplit=4k/10:64k/50:32k/40
1477 Ordering does not matter. If the percentage is left blank, fio will
1478 fill in the remaining values evenly. So a bssplit option like this one::
1480 bssplit=4k/50:1k/:32k/
1482 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always
1483 add up to 100, if bssplit is given a range that adds up to more, it
1486 Comma-separated values may be specified for reads, writes, and trims as
1487 described in :option:`blocksize`.
1489 If you want a workload that has 50% 2k reads and 50% 4k reads, while
1490 having 90% 4k writes and 10% 8k writes, you would specify::
1492 bssplit=2k/50:4k/50,4k/90:8k/10
1494 Fio supports defining up to 64 different weights for each data
1497 .. option:: blocksize_unaligned, bs_unaligned
1499 If set, fio will issue I/O units with any size within
1500 :option:`blocksize_range`, not just multiples of the minimum size. This
1501 typically won't work with direct I/O, as that normally requires sector
1504 .. option:: bs_is_seq_rand=bool
1506 If this option is set, fio will use the normal read,write blocksize settings
1507 as sequential,random blocksize settings instead. Any random read or write
1508 will use the WRITE blocksize settings, and any sequential read or write will
1509 use the READ blocksize settings.
1511 .. option:: blockalign=int[,int][,int], ba=int[,int][,int]
1513 Boundary to which fio will align random I/O units. Default:
1514 :option:`blocksize`. Minimum alignment is typically 512b for using direct
1515 I/O, though it usually depends on the hardware block size. This option is
1516 mutually exclusive with using a random map for files, so it will turn off
1517 that option. Comma-separated values may be specified for reads, writes, and
1518 trims as described in :option:`blocksize`.
1524 .. option:: zero_buffers
1526 Initialize buffers with all zeros. Default: fill buffers with random data.
1528 .. option:: refill_buffers
1530 If this option is given, fio will refill the I/O buffers on every
1531 submit. Only makes sense if :option:`zero_buffers` isn't specified,
1532 naturally. Defaults to being unset i.e., the buffer is only filled at
1533 init time and the data in it is reused when possible but if any of
1534 :option:`verify`, :option:`buffer_compress_percentage` or
1535 :option:`dedupe_percentage` are enabled then `refill_buffers` is also
1536 automatically enabled.
1538 .. option:: scramble_buffers=bool
1540 If :option:`refill_buffers` is too costly and the target is using data
1541 deduplication, then setting this option will slightly modify the I/O buffer
1542 contents to defeat normal de-dupe attempts. This is not enough to defeat
1543 more clever block compression attempts, but it will stop naive dedupe of
1544 blocks. Default: true.
1546 .. option:: buffer_compress_percentage=int
1548 If this is set, then fio will attempt to provide I/O buffer content
1549 (on WRITEs) that compresses to the specified level. Fio does this by
1550 providing a mix of random data followed by fixed pattern data. The
1551 fixed pattern is either zeros, or the pattern specified by
1552 :option:`buffer_pattern`. If the `buffer_pattern` option is used, it
1553 might skew the compression ratio slightly. Setting
1554 `buffer_compress_percentage` to a value other than 100 will also
1555 enable :option:`refill_buffers` in order to reduce the likelihood that
1556 adjacent blocks are so similar that they over compress when seen
1557 together. See :option:`buffer_compress_chunk` for how to set a finer or
1558 coarser granularity for the random/fixed data region. Defaults to unset
1559 i.e., buffer data will not adhere to any compression level.
1561 .. option:: buffer_compress_chunk=int
1563 This setting allows fio to manage how big the random/fixed data region
1564 is when using :option:`buffer_compress_percentage`. When
1565 `buffer_compress_chunk` is set to some non-zero value smaller than the
1566 block size, fio can repeat the random/fixed region throughout the I/O
1567 buffer at the specified interval (which particularly useful when
1568 bigger block sizes are used for a job). When set to 0, fio will use a
1569 chunk size that matches the block size resulting in a single
1570 random/fixed region within the I/O buffer. Defaults to 512. When the
1571 unit is omitted, the value is interpreted in bytes.
1573 .. option:: buffer_pattern=str
1575 If set, fio will fill the I/O buffers with this pattern or with the contents
1576 of a file. If not set, the contents of I/O buffers are defined by the other
1577 options related to buffer contents. The setting can be any pattern of bytes,
1578 and can be prefixed with 0x for hex values. It may also be a string, where
1579 the string must then be wrapped with ``""``. Or it may also be a filename,
1580 where the filename must be wrapped with ``''`` in which case the file is
1581 opened and read. Note that not all the file contents will be read if that
1582 would cause the buffers to overflow. So, for example::
1584 buffer_pattern='filename'
1588 buffer_pattern="abcd"
1596 buffer_pattern=0xdeadface
1598 Also you can combine everything together in any order::
1600 buffer_pattern=0xdeadface"abcd"-12'filename'
1602 .. option:: dedupe_percentage=int
1604 If set, fio will generate this percentage of identical buffers when
1605 writing. These buffers will be naturally dedupable. The contents of the
1606 buffers depend on what other buffer compression settings have been set. It's
1607 possible to have the individual buffers either fully compressible, or not at
1608 all -- this option only controls the distribution of unique buffers. Setting
1609 this option will also enable :option:`refill_buffers` to prevent every buffer
1612 .. option:: invalidate=bool
1614 Invalidate the buffer/page cache parts of the files to be used prior to
1615 starting I/O if the platform and file type support it. Defaults to true.
1616 This will be ignored if :option:`pre_read` is also specified for the
1619 .. option:: sync=bool
1621 Use synchronous I/O for buffered writes. For the majority of I/O engines,
1622 this means using O_SYNC. Default: false.
1624 .. option:: iomem=str, mem=str
1626 Fio can use various types of memory as the I/O unit buffer. The allowed
1630 Use memory from :manpage:`malloc(3)` as the buffers. Default memory
1634 Use shared memory as the buffers. Allocated through
1635 :manpage:`shmget(2)`.
1638 Same as shm, but use huge pages as backing.
1641 Use :manpage:`mmap(2)` to allocate buffers. May either be anonymous memory, or can
1642 be file backed if a filename is given after the option. The format
1643 is `mem=mmap:/path/to/file`.
1646 Use a memory mapped huge file as the buffer backing. Append filename
1647 after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file`.
1650 Same as mmap, but use a MMAP_SHARED mapping.
1653 Use GPU memory as the buffers for GPUDirect RDMA benchmark.
1654 The :option:`ioengine` must be `rdma`.
1656 The area allocated is a function of the maximum allowed bs size for the job,
1657 multiplied by the I/O depth given. Note that for **shmhuge** and
1658 **mmaphuge** to work, the system must have free huge pages allocated. This
1659 can normally be checked and set by reading/writing
1660 :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page
1661 is 4MiB in size. So to calculate the number of huge pages you need for a
1662 given job file, add up the I/O depth of all jobs (normally one unless
1663 :option:`iodepth` is used) and multiply by the maximum bs set. Then divide
1664 that number by the huge page size. You can see the size of the huge pages in
1665 :file:`/proc/meminfo`. If no huge pages are allocated by having a non-zero
1666 number in `nr_hugepages`, using **mmaphuge** or **shmhuge** will fail. Also
1667 see :option:`hugepage-size`.
1669 **mmaphuge** also needs to have hugetlbfs mounted and the file location
1670 should point there. So if it's mounted in :file:`/huge`, you would use
1671 `mem=mmaphuge:/huge/somefile`.
1673 .. option:: iomem_align=int, mem_align=int
1675 This indicates the memory alignment of the I/O memory buffers. Note that
1676 the given alignment is applied to the first I/O unit buffer, if using
1677 :option:`iodepth` the alignment of the following buffers are given by the
1678 :option:`bs` used. In other words, if using a :option:`bs` that is a
1679 multiple of the page sized in the system, all buffers will be aligned to
1680 this value. If using a :option:`bs` that is not page aligned, the alignment
1681 of subsequent I/O memory buffers is the sum of the :option:`iomem_align` and
1684 .. option:: hugepage-size=int
1686 Defines the size of a huge page. Must at least be equal to the system
1687 setting, see :file:`/proc/meminfo`. Defaults to 4MiB. Should probably
1688 always be a multiple of megabytes, so using ``hugepage-size=Xm`` is the
1689 preferred way to set this to avoid setting a non-pow-2 bad value.
1691 .. option:: lockmem=int
1693 Pin the specified amount of memory with :manpage:`mlock(2)`. Can be used to
1694 simulate a smaller amount of memory. The amount specified is per worker.
1700 .. option:: size=int
1702 The total size of file I/O for each thread of this job. Fio will run until
1703 this many bytes has been transferred, unless runtime is limited by other options
1704 (such as :option:`runtime`, for instance, or increased/decreased by :option:`io_size`).
1705 Fio will divide this size between the available files determined by options
1706 such as :option:`nrfiles`, :option:`filename`, unless :option:`filesize` is
1707 specified by the job. If the result of division happens to be 0, the size is
1708 set to the physical size of the given files or devices if they exist.
1709 If this option is not specified, fio will use the full size of the given
1710 files or devices. If the files do not exist, size must be given. It is also
1711 possible to give size as a percentage between 1 and 100. If ``size=20%`` is
1712 given, fio will use 20% of the full size of the given files or devices.
1713 Can be combined with :option:`offset` to constrain the start and end range
1714 that I/O will be done within.
1716 .. option:: io_size=int, io_limit=int
1718 Normally fio operates within the region set by :option:`size`, which means
1719 that the :option:`size` option sets both the region and size of I/O to be
1720 performed. Sometimes that is not what you want. With this option, it is
1721 possible to define just the amount of I/O that fio should do. For instance,
1722 if :option:`size` is set to 20GiB and :option:`io_size` is set to 5GiB, fio
1723 will perform I/O within the first 20GiB but exit when 5GiB have been
1724 done. The opposite is also possible -- if :option:`size` is set to 20GiB,
1725 and :option:`io_size` is set to 40GiB, then fio will do 40GiB of I/O within
1726 the 0..20GiB region.
1728 .. option:: filesize=irange(int)
1730 Individual file sizes. May be a range, in which case fio will select sizes
1731 for files at random within the given range and limited to :option:`size` in
1732 total (if that is given). If not given, each created file is the same size.
1733 This option overrides :option:`size` in terms of file size, which means
1734 this value is used as a fixed size or possible range of each file.
1736 .. option:: file_append=bool
1738 Perform I/O after the end of the file. Normally fio will operate within the
1739 size of a file. If this option is set, then fio will append to the file
1740 instead. This has identical behavior to setting :option:`offset` to the size
1741 of a file. This option is ignored on non-regular files.
1743 .. option:: fill_device=bool, fill_fs=bool
1745 Sets size to something really large and waits for ENOSPC (no space left on
1746 device) as the terminating condition. Only makes sense with sequential
1747 write. For a read workload, the mount point will be filled first then I/O
1748 started on the result. This option doesn't make sense if operating on a raw
1749 device node, since the size of that is already known by the file system.
1750 Additionally, writing beyond end-of-device will not return ENOSPC there.
1756 .. option:: ioengine=str
1758 Defines how the job issues I/O to the file. The following types are defined:
1761 Basic :manpage:`read(2)` or :manpage:`write(2)`
1762 I/O. :manpage:`lseek(2)` is used to position the I/O location.
1763 See :option:`fsync` and :option:`fdatasync` for syncing write I/Os.
1766 Basic :manpage:`pread(2)` or :manpage:`pwrite(2)` I/O. Default on
1767 all supported operating systems except for Windows.
1770 Basic :manpage:`readv(2)` or :manpage:`writev(2)` I/O. Will emulate
1771 queuing by coalescing adjacent I/Os into a single submission.
1774 Basic :manpage:`preadv(2)` or :manpage:`pwritev(2)` I/O.
1777 Basic :manpage:`preadv2(2)` or :manpage:`pwritev2(2)` I/O.
1780 Linux native asynchronous I/O. Note that Linux may only support
1781 queued behavior with non-buffered I/O (set ``direct=1`` or
1783 This engine defines engine specific options.
1786 POSIX asynchronous I/O using :manpage:`aio_read(3)` and
1787 :manpage:`aio_write(3)`.
1790 Solaris native asynchronous I/O.
1793 Windows native asynchronous I/O. Default on Windows.
1796 File is memory mapped with :manpage:`mmap(2)` and data copied
1797 to/from using :manpage:`memcpy(3)`.
1800 :manpage:`splice(2)` is used to transfer the data and
1801 :manpage:`vmsplice(2)` to transfer data from user space to the
1805 SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
1806 ioctl, or if the target is an sg character device we use
1807 :manpage:`read(2)` and :manpage:`write(2)` for asynchronous
1808 I/O. Requires :option:`filename` option to specify either block or
1809 character devices. This engine supports trim operations.
1810 The sg engine includes engine specific options.
1813 Doesn't transfer any data, just pretends to. This is mainly used to
1814 exercise fio itself and for debugging/testing purposes.
1817 Transfer over the network to given ``host:port``. Depending on the
1818 :option:`protocol` used, the :option:`hostname`, :option:`port`,
1819 :option:`listen` and :option:`filename` options are used to specify
1820 what sort of connection to make, while the :option:`protocol` option
1821 determines which protocol will be used. This engine defines engine
1825 Like **net**, but uses :manpage:`splice(2)` and
1826 :manpage:`vmsplice(2)` to map data and send/receive.
1827 This engine defines engine specific options.
1830 Doesn't transfer any data, but burns CPU cycles according to the
1831 :option:`cpuload` and :option:`cpuchunks` options. Setting
1832 :option:`cpuload`\=85 will cause that job to do nothing but burn 85%
1833 of the CPU. In case of SMP machines, use :option:`numjobs`\=<nr_of_cpu>
1834 to get desired CPU usage, as the cpuload only loads a
1835 single CPU at the desired rate. A job never finishes unless there is
1836 at least one non-cpuio job.
1839 The GUASI I/O engine is the Generic Userspace Asynchronous Syscall
1840 Interface approach to async I/O. See
1842 http://www.xmailserver.org/guasi-lib.html
1844 for more info on GUASI.
1847 The RDMA I/O engine supports both RDMA memory semantics
1848 (RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
1849 InfiniBand, RoCE and iWARP protocols. This engine defines engine
1853 I/O engine that does regular fallocate to simulate data transfer as
1857 does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
1860 does fallocate(,mode = 0).
1863 does fallocate(,mode = FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
1866 I/O engine that sends :manpage:`ftruncate(2)` operations in response
1867 to write (DDIR_WRITE) events. Each ftruncate issued sets the file's
1868 size to the current block offset. :option:`blocksize` is ignored.
1871 I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
1872 defragment activity in request to DDIR_WRITE event.
1875 I/O engine supporting direct access to Ceph Reliable Autonomic
1876 Distributed Object Store (RADOS) via librados. This ioengine
1877 defines engine specific options.
1880 I/O engine supporting direct access to Ceph Rados Block Devices
1881 (RBD) via librbd without the need to use the kernel rbd driver. This
1882 ioengine defines engine specific options.
1885 I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to
1886 a WebDAV or S3 endpoint. This ioengine defines engine specific options.
1888 This engine only supports direct IO of iodepth=1; you need to scale this
1889 via numjobs. blocksize defines the size of the objects to be created.
1891 TRIM is translated to object deletion.
1894 Using GlusterFS libgfapi sync interface to direct access to
1895 GlusterFS volumes without having to go through FUSE. This ioengine
1896 defines engine specific options.
1899 Using GlusterFS libgfapi async interface to direct access to
1900 GlusterFS volumes without having to go through FUSE. This ioengine
1901 defines engine specific options.
1904 Read and write through Hadoop (HDFS). The :option:`filename` option
1905 is used to specify host,port of the hdfs name-node to connect. This
1906 engine interprets offsets a little differently. In HDFS, files once
1907 created cannot be modified so random writes are not possible. To
1908 imitate this the libhdfs engine expects a bunch of small files to be
1909 created over HDFS and will randomly pick a file from them
1910 based on the offset generated by fio backend (see the example
1911 job file to create such files, use ``rw=write`` option). Please
1912 note, it may be necessary to set environment variables to work
1913 with HDFS/libhdfs properly. Each job uses its own connection to
1917 Read, write and erase an MTD character device (e.g.,
1918 :file:`/dev/mtd0`). Discards are treated as erases. Depending on the
1919 underlying device type, the I/O may have to go in a certain pattern,
1920 e.g., on NAND, writing sequentially to erase blocks and discarding
1921 before overwriting. The `trimwrite` mode works well for this
1925 Read and write using filesystem DAX to a file on a filesystem
1926 mounted with DAX on a persistent memory device through the PMDK
1930 Read and write using device DAX to a persistent memory device (e.g.,
1931 /dev/dax0.0) through the PMDK libpmem library.
1934 Prefix to specify loading an external I/O engine object file. Append
1935 the engine filename, e.g. ``ioengine=external:/tmp/foo.o`` to load
1936 ioengine :file:`foo.o` in :file:`/tmp`. The path can be either
1937 absolute or relative. See :file:`engines/skeleton_external.c` for
1938 details of writing an external I/O engine.
1941 Simply create the files and do no I/O to them. You still need to
1942 set `filesize` so that all the accounting still occurs, but no
1943 actual I/O will be done other than creating the file.
1946 Read and write using mmap I/O to a file on a filesystem
1947 mounted with DAX on a persistent memory device through the PMDK
1951 Synchronous read and write using DDN's Infinite Memory Engine (IME).
1952 This engine is very basic and issues calls to IME whenever an IO is
1956 Synchronous read and write using DDN's Infinite Memory Engine (IME).
1957 This engine uses iovecs and will try to stack as much IOs as possible
1958 (if the IOs are "contiguous" and the IO depth is not exceeded)
1959 before issuing a call to IME.
1962 Asynchronous read and write using DDN's Infinite Memory Engine (IME).
1963 This engine will try to stack as much IOs as possible by creating
1964 requests for IME. FIO will then decide when to commit these requests.
1966 I/O engine specific parameters
1967 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1969 In addition, there are some parameters which are only valid when a specific
1970 :option:`ioengine` is in use. These are used identically to normal parameters,
1971 with the caveat that when used on the command line, they must come after the
1972 :option:`ioengine` that defines them is selected.
1974 .. option:: userspace_reap : [libaio]
1976 Normally, with the libaio engine in use, fio will use the
1977 :manpage:`io_getevents(2)` system call to reap newly returned events. With
1978 this flag turned on, the AIO ring will be read directly from user-space to
1979 reap events. The reaping mode is only enabled when polling for a minimum of
1980 0 events (e.g. when :option:`iodepth_batch_complete` `=0`).
1982 .. option:: hipri : [pvsync2]
1984 Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority
1987 .. option:: hipri_percentage : [pvsync2]
1989 When hipri is set this determines the probability of a pvsync2 I/O being high
1990 priority. The default is 100%.
1992 .. option:: cpuload=int : [cpuio]
1994 Attempt to use the specified percentage of CPU cycles. This is a mandatory
1995 option when using cpuio I/O engine.
1997 .. option:: cpuchunks=int : [cpuio]
1999 Split the load into cycles of the given time. In microseconds.
2001 .. option:: exit_on_io_done=bool : [cpuio]
2003 Detect when I/O threads are done, then exit.
2005 .. option:: namenode=str : [libhdfs]
2007 The hostname or IP address of a HDFS cluster namenode to contact.
2009 .. option:: port=int
2013 The listening port of the HFDS cluster namenode.
2017 The TCP or UDP port to bind to or connect to. If this is used with
2018 :option:`numjobs` to spawn multiple instances of the same job type, then
2019 this will be the starting port number since fio will use a range of
2024 The port to use for RDMA-CM communication. This should be the same value
2025 on the client and the server side.
2027 .. option:: hostname=str : [netsplice] [net] [rdma]
2029 The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If the job
2030 is a TCP listener or UDP reader, the hostname is not used and must be omitted
2031 unless it is a valid UDP multicast address.
2033 .. option:: interface=str : [netsplice] [net]
2035 The IP address of the network interface used to send or receive UDP
2038 .. option:: ttl=int : [netsplice] [net]
2040 Time-to-live value for outgoing UDP multicast packets. Default: 1.
2042 .. option:: nodelay=bool : [netsplice] [net]
2044 Set TCP_NODELAY on TCP connections.
2046 .. option:: protocol=str, proto=str : [netsplice] [net]
2048 The network protocol to use. Accepted values are:
2051 Transmission control protocol.
2053 Transmission control protocol V6.
2055 User datagram protocol.
2057 User datagram protocol V6.
2061 When the protocol is TCP or UDP, the port must also be given, as well as the
2062 hostname if the job is a TCP listener or UDP reader. For unix sockets, the
2063 normal :option:`filename` option should be used and the port is invalid.
2065 .. option:: listen : [netsplice] [net]
2067 For TCP network connections, tell fio to listen for incoming connections
2068 rather than initiating an outgoing connection. The :option:`hostname` must
2069 be omitted if this option is used.
2071 .. option:: pingpong : [netsplice] [net]
2073 Normally a network writer will just continue writing data, and a network
2074 reader will just consume packages. If ``pingpong=1`` is set, a writer will
2075 send its normal payload to the reader, then wait for the reader to send the
2076 same payload back. This allows fio to measure network latencies. The
2077 submission and completion latencies then measure local time spent sending or
2078 receiving, and the completion latency measures how long it took for the
2079 other end to receive and send back. For UDP multicast traffic
2080 ``pingpong=1`` should only be set for a single reader when multiple readers
2081 are listening to the same address.
2083 .. option:: window_size : [netsplice] [net]
2085 Set the desired socket buffer size for the connection.
2087 .. option:: mss : [netsplice] [net]
2089 Set the TCP maximum segment size (TCP_MAXSEG).
2091 .. option:: donorname=str : [e4defrag]
2093 File will be used as a block donor (swap extents between files).
2095 .. option:: inplace=int : [e4defrag]
2097 Configure donor file blocks allocation strategy:
2100 Default. Preallocate donor's file on init.
2102 Allocate space immediately inside defragment event, and free right
2105 .. option:: clustername=str : [rbd,rados]
2107 Specifies the name of the Ceph cluster.
2109 .. option:: rbdname=str : [rbd]
2111 Specifies the name of the RBD.
2113 .. option:: pool=str : [rbd,rados]
2115 Specifies the name of the Ceph pool containing RBD or RADOS data.
2117 .. option:: clientname=str : [rbd,rados]
2119 Specifies the username (without the 'client.' prefix) used to access the
2120 Ceph cluster. If the *clustername* is specified, the *clientname* shall be
2121 the full *type.id* string. If no type. prefix is given, fio will add
2122 'client.' by default.
2124 .. option:: busy_poll=bool : [rbd,rados]
2126 Poll store instead of waiting for completion. Usually this provides better
2127 throughput at cost of higher(up to 100%) CPU utilization.
2129 .. option:: skip_bad=bool : [mtd]
2131 Skip operations against known bad blocks.
2133 .. option:: hdfsdirectory : [libhdfs]
2135 libhdfs will create chunk in this HDFS directory.
2137 .. option:: chunk_size : [libhdfs]
2139 The size of the chunk to use for each file.
2141 .. option:: verb=str : [rdma]
2143 The RDMA verb to use on this side of the RDMA ioengine connection. Valid
2144 values are write, read, send and recv. These correspond to the equivalent
2145 RDMA verbs (e.g. write = rdma_write etc.). Note that this only needs to be
2146 specified on the client side of the connection. See the examples folder.
2148 .. option:: bindname=str : [rdma]
2150 The name to use to bind the local RDMA-CM connection to a local RDMA device.
2151 This could be a hostname or an IPv4 or IPv6 address. On the server side this
2152 will be passed into the rdma_bind_addr() function and on the client site it
2153 will be used in the rdma_resolve_add() function. This can be useful when
2154 multiple paths exist between the client and the server or in certain loopback
2157 .. option:: readfua=bool : [sg]
2159 With readfua option set to 1, read operations include
2160 the force unit access (fua) flag. Default is 0.
2162 .. option:: writefua=bool : [sg]
2164 With writefua option set to 1, write operations include
2165 the force unit access (fua) flag. Default is 0.
2167 .. option:: sg_write_mode=str : [sg]
2169 Specify the type of write commands to issue. This option can take three values:
2172 This is the default where write opcodes are issued as usual.
2174 Issue WRITE AND VERIFY commands. The BYTCHK bit is set to 0. This
2175 directs the device to carry out a medium verification with no data
2176 comparison. The writefua option is ignored with this selection.
2178 Issue WRITE SAME commands. This transfers a single block to the device
2179 and writes this same block of data to a contiguous sequence of LBAs
2180 beginning at the specified offset. fio's block size parameter specifies
2181 the amount of data written with each command. However, the amount of data
2182 actually transferred to the device is equal to the device's block
2183 (sector) size. For a device with 512 byte sectors, blocksize=8k will
2184 write 16 sectors with each command. fio will still generate 8k of data
2185 for each command but only the first 512 bytes will be used and
2186 transferred to the device. The writefua option is ignored with this
2189 .. option:: http_host=str : [http]
2191 Hostname to connect to. For S3, this could be the bucket hostname.
2192 Default is **localhost**
2194 .. option:: http_user=str : [http]
2196 Username for HTTP authentication.
2198 .. option:: http_pass=str : [http]
2200 Password for HTTP authentication.
2202 .. option:: https=str : [http]
2204 Enable HTTPS instead of http. *on* enables HTTPS; *insecure*
2205 will enable HTTPS, but disable SSL peer verification (use with
2206 caution!). Default is **off**
2208 .. option:: http_mode=str : [http]
2210 Which HTTP access mode to use: *webdav*, *swift*, or *s3*.
2211 Default is **webdav**
2213 .. option:: http_s3_region=str : [http]
2215 The S3 region/zone string.
2216 Default is **us-east-1**
2218 .. option:: http_s3_key=str : [http]
2222 .. option:: http_s3_keyid=str : [http]
2224 The S3 key/access id.
2226 .. option:: http_swift_auth_token=str : [http]
2228 The Swift auth token. See the example configuration file on how
2231 .. option:: http_verbose=int : [http]
2233 Enable verbose requests from libcurl. Useful for debugging. 1
2234 turns on verbose logging from libcurl, 2 additionally enables
2235 HTTP IO tracing. Default is **0**
2240 .. option:: iodepth=int
2242 Number of I/O units to keep in flight against the file. Note that
2243 increasing *iodepth* beyond 1 will not affect synchronous ioengines (except
2244 for small degrees when :option:`verify_async` is in use). Even async
2245 engines may impose OS restrictions causing the desired depth not to be
2246 achieved. This may happen on Linux when using libaio and not setting
2247 :option:`direct`\=1, since buffered I/O is not async on that OS. Keep an
2248 eye on the I/O depth distribution in the fio output to verify that the
2249 achieved depth is as expected. Default: 1.
2251 .. option:: iodepth_batch_submit=int, iodepth_batch=int
2253 This defines how many pieces of I/O to submit at once. It defaults to 1
2254 which means that we submit each I/O as soon as it is available, but can be
2255 raised to submit bigger batches of I/O at the time. If it is set to 0 the
2256 :option:`iodepth` value will be used.
2258 .. option:: iodepth_batch_complete_min=int, iodepth_batch_complete=int
2260 This defines how many pieces of I/O to retrieve at once. It defaults to 1
2261 which means that we'll ask for a minimum of 1 I/O in the retrieval process
2262 from the kernel. The I/O retrieval will go on until we hit the limit set by
2263 :option:`iodepth_low`. If this variable is set to 0, then fio will always
2264 check for completed events before queuing more I/O. This helps reduce I/O
2265 latency, at the cost of more retrieval system calls.
2267 .. option:: iodepth_batch_complete_max=int
2269 This defines maximum pieces of I/O to retrieve at once. This variable should
2270 be used along with :option:`iodepth_batch_complete_min`\=int variable,
2271 specifying the range of min and max amount of I/O which should be
2272 retrieved. By default it is equal to the :option:`iodepth_batch_complete_min`
2277 iodepth_batch_complete_min=1
2278 iodepth_batch_complete_max=<iodepth>
2280 which means that we will retrieve at least 1 I/O and up to the whole
2281 submitted queue depth. If none of I/O has been completed yet, we will wait.
2285 iodepth_batch_complete_min=0
2286 iodepth_batch_complete_max=<iodepth>
2288 which means that we can retrieve up to the whole submitted queue depth, but
2289 if none of I/O has been completed yet, we will NOT wait and immediately exit
2290 the system call. In this example we simply do polling.
2292 .. option:: iodepth_low=int
2294 The low water mark indicating when to start filling the queue
2295 again. Defaults to the same as :option:`iodepth`, meaning that fio will
2296 attempt to keep the queue full at all times. If :option:`iodepth` is set to
2297 e.g. 16 and *iodepth_low* is set to 4, then after fio has filled the queue of
2298 16 requests, it will let the depth drain down to 4 before starting to fill
2301 .. option:: serialize_overlap=bool
2303 Serialize in-flight I/Os that might otherwise cause or suffer from data races.
2304 When two or more I/Os are submitted simultaneously, there is no guarantee that
2305 the I/Os will be processed or completed in the submitted order. Further, if
2306 two or more of those I/Os are writes, any overlapping region between them can
2307 become indeterminate/undefined on certain storage. These issues can cause
2308 verification to fail erratically when at least one of the racing I/Os is
2309 changing data and the overlapping region has a non-zero size. Setting
2310 ``serialize_overlap`` tells fio to avoid provoking this behavior by explicitly
2311 serializing in-flight I/Os that have a non-zero overlap. Note that setting
2312 this option can reduce both performance and the :option:`iodepth` achieved.
2313 Additionally this option does not work when :option:`io_submit_mode` is set to
2314 offload. Default: false.
2316 .. option:: io_submit_mode=str
2318 This option controls how fio submits the I/O to the I/O engine. The default
2319 is `inline`, which means that the fio job threads submit and reap I/O
2320 directly. If set to `offload`, the job threads will offload I/O submission
2321 to a dedicated pool of I/O threads. This requires some coordination and thus
2322 has a bit of extra overhead, especially for lower queue depth I/O where it
2323 can increase latencies. The benefit is that fio can manage submission rates
2324 independently of the device completion rates. This avoids skewed latency
2325 reporting if I/O gets backed up on the device side (the coordinated omission
2332 .. option:: thinktime=time
2334 Stall the job for the specified period of time after an I/O has completed before issuing the
2335 next. May be used to simulate processing being done by an application.
2336 When the unit is omitted, the value is interpreted in microseconds. See
2337 :option:`thinktime_blocks` and :option:`thinktime_spin`.
2339 .. option:: thinktime_spin=time
2341 Only valid if :option:`thinktime` is set - pretend to spend CPU time doing
2342 something with the data received, before falling back to sleeping for the
2343 rest of the period specified by :option:`thinktime`. When the unit is
2344 omitted, the value is interpreted in microseconds.
2346 .. option:: thinktime_blocks=int
2348 Only valid if :option:`thinktime` is set - control how many blocks to issue,
2349 before waiting :option:`thinktime` usecs. If not set, defaults to 1 which will make
2350 fio wait :option:`thinktime` usecs after every block. This effectively makes any
2351 queue depth setting redundant, since no more than 1 I/O will be queued
2352 before we have to complete it and do our :option:`thinktime`. In other words, this
2353 setting effectively caps the queue depth if the latter is larger.
2355 .. option:: rate=int[,int][,int]
2357 Cap the bandwidth used by this job. The number is in bytes/sec, the normal
2358 suffix rules apply. Comma-separated values may be specified for reads,
2359 writes, and trims as described in :option:`blocksize`.
2361 For example, using `rate=1m,500k` would limit reads to 1MiB/sec and writes to
2362 500KiB/sec. Capping only reads or writes can be done with `rate=,500k` or
2363 `rate=500k,` where the former will only limit writes (to 500KiB/sec) and the
2364 latter will only limit reads.
2366 .. option:: rate_min=int[,int][,int]
2368 Tell fio to do whatever it can to maintain at least this bandwidth. Failing
2369 to meet this requirement will cause the job to exit. Comma-separated values
2370 may be specified for reads, writes, and trims as described in
2371 :option:`blocksize`.
2373 .. option:: rate_iops=int[,int][,int]
2375 Cap the bandwidth to this number of IOPS. Basically the same as
2376 :option:`rate`, just specified independently of bandwidth. If the job is
2377 given a block size range instead of a fixed value, the smallest block size
2378 is used as the metric. Comma-separated values may be specified for reads,
2379 writes, and trims as described in :option:`blocksize`.
2381 .. option:: rate_iops_min=int[,int][,int]
2383 If fio doesn't meet this rate of I/O, it will cause the job to exit.
2384 Comma-separated values may be specified for reads, writes, and trims as
2385 described in :option:`blocksize`.
2387 .. option:: rate_process=str
2389 This option controls how fio manages rated I/O submissions. The default is
2390 `linear`, which submits I/O in a linear fashion with fixed delays between
2391 I/Os that gets adjusted based on I/O completion rates. If this is set to
2392 `poisson`, fio will submit I/O based on a more real world random request
2393 flow, known as the Poisson process
2394 (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be
2395 10^6 / IOPS for the given workload.
2397 .. option:: rate_ignore_thinktime=bool
2399 By default, fio will attempt to catch up to the specified rate setting,
2400 if any kind of thinktime setting was used. If this option is set, then
2401 fio will ignore the thinktime and continue doing IO at the specified
2402 rate, instead of entering a catch-up mode after thinktime is done.
2408 .. option:: latency_target=time
2410 If set, fio will attempt to find the max performance point that the given
2411 workload will run at while maintaining a latency below this target. When
2412 the unit is omitted, the value is interpreted in microseconds. See
2413 :option:`latency_window` and :option:`latency_percentile`.
2415 .. option:: latency_window=time
2417 Used with :option:`latency_target` to specify the sample window that the job
2418 is run at varying queue depths to test the performance. When the unit is
2419 omitted, the value is interpreted in microseconds.
2421 .. option:: latency_percentile=float
2423 The percentage of I/Os that must fall within the criteria specified by
2424 :option:`latency_target` and :option:`latency_window`. If not set, this
2425 defaults to 100.0, meaning that all I/Os must be equal or below to the value
2426 set by :option:`latency_target`.
2428 .. option:: max_latency=time
2430 If set, fio will exit the job with an ETIMEDOUT error if it exceeds this
2431 maximum latency. When the unit is omitted, the value is interpreted in
2434 .. option:: rate_cycle=int
2436 Average bandwidth for :option:`rate` and :option:`rate_min` over this number
2437 of milliseconds. Defaults to 1000.
2443 .. option:: write_iolog=str
2445 Write the issued I/O patterns to the specified file. See
2446 :option:`read_iolog`. Specify a separate file for each job, otherwise the
2447 iologs will be interspersed and the file may be corrupt.
2449 .. option:: read_iolog=str
2451 Open an iolog with the specified filename and replay the I/O patterns it
2452 contains. This can be used to store a workload and replay it sometime
2453 later. The iolog given may also be a blktrace binary file, which allows fio
2454 to replay a workload captured by :command:`blktrace`. See
2455 :manpage:`blktrace(8)` for how to capture such logging data. For blktrace
2456 replay, the file needs to be turned into a blkparse binary data file first
2457 (``blkparse <device> -o /dev/null -d file_for_fio.bin``).
2458 You can specify a number of files by separating the names with a ':'
2459 character. See the :option:`filename` option for information on how to
2460 escape ':' and '\' characters within the file names. These files will
2461 be sequentially assigned to job clones created by :option:`numjobs`.
2463 .. option:: read_iolog_chunked=bool
2465 Determines how iolog is read. If false(default) entire :option:`read_iolog`
2466 will be read at once. If selected true, input from iolog will be read
2467 gradually. Useful when iolog is very large, or it is generated.
2469 .. option:: replay_no_stall=bool
2471 When replaying I/O with :option:`read_iolog` the default behavior is to
2472 attempt to respect the timestamps within the log and replay them with the
2473 appropriate delay between IOPS. By setting this variable fio will not
2474 respect the timestamps and attempt to replay them as fast as possible while
2475 still respecting ordering. The result is the same I/O pattern to a given
2476 device, but different timings.
2478 .. option:: replay_time_scale=int
2480 When replaying I/O with :option:`read_iolog`, fio will honor the
2481 original timing in the trace. With this option, it's possible to scale
2482 the time. It's a percentage option, if set to 50 it means run at 50%
2483 the original IO rate in the trace. If set to 200, run at twice the
2484 original IO rate. Defaults to 100.
2486 .. option:: replay_redirect=str
2488 While replaying I/O patterns using :option:`read_iolog` the default behavior
2489 is to replay the IOPS onto the major/minor device that each IOP was recorded
2490 from. This is sometimes undesirable because on a different machine those
2491 major/minor numbers can map to a different device. Changing hardware on the
2492 same system can also result in a different major/minor mapping.
2493 ``replay_redirect`` causes all I/Os to be replayed onto the single specified
2494 device regardless of the device it was recorded
2495 from. i.e. :option:`replay_redirect`\= :file:`/dev/sdc` would cause all I/O
2496 in the blktrace or iolog to be replayed onto :file:`/dev/sdc`. This means
2497 multiple devices will be replayed onto a single device, if the trace
2498 contains multiple devices. If you want multiple devices to be replayed
2499 concurrently to multiple redirected devices you must blkparse your trace
2500 into separate traces and replay them with independent fio invocations.
2501 Unfortunately this also breaks the strict time ordering between multiple
2504 .. option:: replay_align=int
2506 Force alignment of I/O offsets and lengths in a trace to this power of 2
2509 .. option:: replay_scale=int
2511 Scale sector offsets down by this factor when replaying traces.
2513 .. option:: replay_skip=str
2515 Sometimes it's useful to skip certain IO types in a replay trace.
2516 This could be, for instance, eliminating the writes in the trace.
2517 Or not replaying the trims/discards, if you are redirecting to
2518 a device that doesn't support them. This option takes a comma
2519 separated list of read, write, trim, sync.
2522 Threads, processes and job synchronization
2523 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2527 Fio defaults to creating jobs by using fork, however if this option is
2528 given, fio will create jobs by using POSIX Threads' function
2529 :manpage:`pthread_create(3)` to create threads instead.
2531 .. option:: wait_for=str
2533 If set, the current job won't be started until all workers of the specified
2534 waitee job are done.
2536 ``wait_for`` operates on the job name basis, so there are a few
2537 limitations. First, the waitee must be defined prior to the waiter job
2538 (meaning no forward references). Second, if a job is being referenced as a
2539 waitee, it must have a unique name (no duplicate waitees).
2541 .. option:: nice=int
2543 Run the job with the given nice value. See man :manpage:`nice(2)`.
2545 On Windows, values less than -15 set the process class to "High"; -1 through
2546 -15 set "Above Normal"; 1 through 15 "Below Normal"; and above 15 "Idle"
2549 .. option:: prio=int
2551 Set the I/O priority value of this job. Linux limits us to a positive value
2552 between 0 and 7, with 0 being the highest. See man
2553 :manpage:`ionice(1)`. Refer to an appropriate manpage for other operating
2554 systems since meaning of priority may differ.
2556 .. option:: prioclass=int
2558 Set the I/O priority class. See man :manpage:`ionice(1)`.
2560 .. option:: cpus_allowed=str
2562 Controls the same options as :option:`cpumask`, but accepts a textual
2563 specification of the permitted CPUs instead and CPUs are indexed from 0. So
2564 to use CPUs 0 and 5 you would specify ``cpus_allowed=0,5``. This option also
2565 allows a range of CPUs to be specified -- say you wanted a binding to CPUs
2566 0, 5, and 8 to 15, you would set ``cpus_allowed=0,5,8-15``.
2568 On Windows, when ``cpus_allowed`` is unset only CPUs from fio's current
2569 processor group will be used and affinity settings are inherited from the
2570 system. An fio build configured to target Windows 7 makes options that set
2571 CPUs processor group aware and values will set both the processor group
2572 and a CPU from within that group. For example, on a system where processor
2573 group 0 has 40 CPUs and processor group 1 has 32 CPUs, ``cpus_allowed``
2574 values between 0 and 39 will bind CPUs from processor group 0 and
2575 ``cpus_allowed`` values between 40 and 71 will bind CPUs from processor
2576 group 1. When using ``cpus_allowed_policy=shared`` all CPUs specified by a
2577 single ``cpus_allowed`` option must be from the same processor group. For
2578 Windows fio builds not built for Windows 7, CPUs will only be selected from
2579 (and be relative to) whatever processor group fio happens to be running in
2580 and CPUs from other processor groups cannot be used.
2582 .. option:: cpus_allowed_policy=str
2584 Set the policy of how fio distributes the CPUs specified by
2585 :option:`cpus_allowed` or :option:`cpumask`. Two policies are supported:
2588 All jobs will share the CPU set specified.
2590 Each job will get a unique CPU from the CPU set.
2592 **shared** is the default behavior, if the option isn't specified. If
2593 **split** is specified, then fio will will assign one cpu per job. If not
2594 enough CPUs are given for the jobs listed, then fio will roundrobin the CPUs
2597 .. option:: cpumask=int
2599 Set the CPU affinity of this job. The parameter given is a bit mask of
2600 allowed CPUs the job may run on. So if you want the allowed CPUs to be 1
2601 and 5, you would pass the decimal value of (1 << 1 | 1 << 5), or 34. See man
2602 :manpage:`sched_setaffinity(2)`. This may not work on all supported
2603 operating systems or kernel versions. This option doesn't work well for a
2604 higher CPU count than what you can store in an integer mask, so it can only
2605 control cpus 1-32. For boxes with larger CPU counts, use
2606 :option:`cpus_allowed`.
2608 .. option:: numa_cpu_nodes=str
2610 Set this job running on specified NUMA nodes' CPUs. The arguments allow
2611 comma delimited list of cpu numbers, A-B ranges, or `all`. Note, to enable
2612 NUMA options support, fio must be built on a system with libnuma-dev(el)
2615 .. option:: numa_mem_policy=str
2617 Set this job's memory policy and corresponding NUMA nodes. Format of the
2622 ``mode`` is one of the following memory policies: ``default``, ``prefer``,
2623 ``bind``, ``interleave`` or ``local``. For ``default`` and ``local`` memory
2624 policies, no node needs to be specified. For ``prefer``, only one node is
2625 allowed. For ``bind`` and ``interleave`` the ``nodelist`` may be as
2626 follows: a comma delimited list of numbers, A-B ranges, or `all`.
2628 .. option:: cgroup=str
2630 Add job to this control group. If it doesn't exist, it will be created. The
2631 system must have a mounted cgroup blkio mount point for this to work. If
2632 your system doesn't have it mounted, you can do so with::
2634 # mount -t cgroup -o blkio none /cgroup
2636 .. option:: cgroup_weight=int
2638 Set the weight of the cgroup to this value. See the documentation that comes
2639 with the kernel, allowed values are in the range of 100..1000.
2641 .. option:: cgroup_nodelete=bool
2643 Normally fio will delete the cgroups it has created after the job
2644 completion. To override this behavior and to leave cgroups around after the
2645 job completion, set ``cgroup_nodelete=1``. This can be useful if one wants
2646 to inspect various cgroup files after job completion. Default: false.
2648 .. option:: flow_id=int
2650 The ID of the flow. If not specified, it defaults to being a global
2651 flow. See :option:`flow`.
2653 .. option:: flow=int
2655 Weight in token-based flow control. If this value is used, then there is a
2656 'flow counter' which is used to regulate the proportion of activity between
2657 two or more jobs. Fio attempts to keep this flow counter near zero. The
2658 ``flow`` parameter stands for how much should be added or subtracted to the
2659 flow counter on each iteration of the main I/O loop. That is, if one job has
2660 ``flow=8`` and another job has ``flow=-1``, then there will be a roughly 1:8
2661 ratio in how much one runs vs the other.
2663 .. option:: flow_watermark=int
2665 The maximum value that the absolute value of the flow counter is allowed to
2666 reach before the job must wait for a lower value of the counter.
2668 .. option:: flow_sleep=int
2670 The period of time, in microseconds, to wait after the flow watermark has
2671 been exceeded before retrying operations.
2673 .. option:: stonewall, wait_for_previous
2675 Wait for preceding jobs in the job file to exit, before starting this
2676 one. Can be used to insert serialization points in the job file. A stone
2677 wall also implies starting a new reporting group, see
2678 :option:`group_reporting`.
2682 By default, fio will continue running all other jobs when one job finishes
2683 but sometimes this is not the desired action. Setting ``exitall`` will
2684 instead make fio terminate all other jobs when one job finishes.
2686 .. option:: exec_prerun=str
2688 Before running this job, issue the command specified through
2689 :manpage:`system(3)`. Output is redirected in a file called
2690 :file:`jobname.prerun.txt`.
2692 .. option:: exec_postrun=str
2694 After the job completes, issue the command specified though
2695 :manpage:`system(3)`. Output is redirected in a file called
2696 :file:`jobname.postrun.txt`.
2700 Instead of running as the invoking user, set the user ID to this value
2701 before the thread/process does any work.
2705 Set group ID, see :option:`uid`.
2711 .. option:: verify_only
2713 Do not perform specified workload, only verify data still matches previous
2714 invocation of this workload. This option allows one to check data multiple
2715 times at a later date without overwriting it. This option makes sense only
2716 for workloads that write data, and does not support workloads with the
2717 :option:`time_based` option set.
2719 .. option:: do_verify=bool
2721 Run the verify phase after a write phase. Only valid if :option:`verify` is
2724 .. option:: verify=str
2726 If writing to a file, fio can verify the file contents after each iteration
2727 of the job. Each verification method also implies verification of special
2728 header, which is written to the beginning of each block. This header also
2729 includes meta information, like offset of the block, block number, timestamp
2730 when block was written, etc. :option:`verify` can be combined with
2731 :option:`verify_pattern` option. The allowed values are:
2734 Use an md5 sum of the data area and store it in the header of
2738 Use an experimental crc64 sum of the data area and store it in the
2739 header of each block.
2742 Use a crc32c sum of the data area and store it in the header of
2743 each block. This will automatically use hardware acceleration
2744 (e.g. SSE4.2 on an x86 or CRC crypto extensions on ARM64) but will
2745 fall back to software crc32c if none is found. Generally the
2746 fastest checksum fio supports when hardware accelerated.
2752 Use a crc32 sum of the data area and store it in the header of each
2756 Use a crc16 sum of the data area and store it in the header of each
2760 Use a crc7 sum of the data area and store it in the header of each
2764 Use xxhash as the checksum function. Generally the fastest software
2765 checksum that fio supports.
2768 Use sha512 as the checksum function.
2771 Use sha256 as the checksum function.
2774 Use optimized sha1 as the checksum function.
2777 Use optimized sha3-224 as the checksum function.
2780 Use optimized sha3-256 as the checksum function.
2783 Use optimized sha3-384 as the checksum function.
2786 Use optimized sha3-512 as the checksum function.
2789 This option is deprecated, since now meta information is included in
2790 generic verification header and meta verification happens by
2791 default. For detailed information see the description of the
2792 :option:`verify` setting. This option is kept because of
2793 compatibility's sake with old configurations. Do not use it.
2796 Verify a strict pattern. Normally fio includes a header with some
2797 basic information and checksumming, but if this option is set, only
2798 the specific pattern set with :option:`verify_pattern` is verified.
2801 Only pretend to verify. Useful for testing internals with
2802 :option:`ioengine`\=null, not for much else.
2804 This option can be used for repeated burn-in tests of a system to make sure
2805 that the written data is also correctly read back. If the data direction
2806 given is a read or random read, fio will assume that it should verify a
2807 previously written file. If the data direction includes any form of write,
2808 the verify will be of the newly written data.
2810 To avoid false verification errors, do not use the norandommap option when
2811 verifying data with async I/O engines and I/O depths > 1. Or use the
2812 norandommap and the lfsr random generator together to avoid writing to the
2813 same offset with muliple outstanding I/Os.
2815 .. option:: verify_offset=int
2817 Swap the verification header with data somewhere else in the block before
2818 writing. It is swapped back before verifying.
2820 .. option:: verify_interval=int
2822 Write the verification header at a finer granularity than the
2823 :option:`blocksize`. It will be written for chunks the size of
2824 ``verify_interval``. :option:`blocksize` should divide this evenly.
2826 .. option:: verify_pattern=str
2828 If set, fio will fill the I/O buffers with this pattern. Fio defaults to
2829 filling with totally random bytes, but sometimes it's interesting to fill
2830 with a known pattern for I/O verification purposes. Depending on the width
2831 of the pattern, fio will fill 1/2/3/4 bytes of the buffer at the time (it can
2832 be either a decimal or a hex number). The ``verify_pattern`` if larger than
2833 a 32-bit quantity has to be a hex number that starts with either "0x" or
2834 "0X". Use with :option:`verify`. Also, ``verify_pattern`` supports %o
2835 format, which means that for each block offset will be written and then
2836 verified back, e.g.::
2840 Or use combination of everything::
2842 verify_pattern=0xff%o"abcd"-12
2844 .. option:: verify_fatal=bool
2846 Normally fio will keep checking the entire contents before quitting on a
2847 block verification failure. If this option is set, fio will exit the job on
2848 the first observed failure. Default: false.
2850 .. option:: verify_dump=bool
2852 If set, dump the contents of both the original data block and the data block
2853 we read off disk to files. This allows later analysis to inspect just what
2854 kind of data corruption occurred. Off by default.
2856 .. option:: verify_async=int
2858 Fio will normally verify I/O inline from the submitting thread. This option
2859 takes an integer describing how many async offload threads to create for I/O
2860 verification instead, causing fio to offload the duty of verifying I/O
2861 contents to one or more separate threads. If using this offload option, even
2862 sync I/O engines can benefit from using an :option:`iodepth` setting higher
2863 than 1, as it allows them to have I/O in flight while verifies are running.
2864 Defaults to 0 async threads, i.e. verification is not asynchronous.
2866 .. option:: verify_async_cpus=str
2868 Tell fio to set the given CPU affinity on the async I/O verification
2869 threads. See :option:`cpus_allowed` for the format used.
2871 .. option:: verify_backlog=int
2873 Fio will normally verify the written contents of a job that utilizes verify
2874 once that job has completed. In other words, everything is written then
2875 everything is read back and verified. You may want to verify continually
2876 instead for a variety of reasons. Fio stores the meta data associated with
2877 an I/O block in memory, so for large verify workloads, quite a bit of memory
2878 would be used up holding this meta data. If this option is enabled, fio will
2879 write only N blocks before verifying these blocks.
2881 .. option:: verify_backlog_batch=int
2883 Control how many blocks fio will verify if :option:`verify_backlog` is
2884 set. If not set, will default to the value of :option:`verify_backlog`
2885 (meaning the entire queue is read back and verified). If
2886 ``verify_backlog_batch`` is less than :option:`verify_backlog` then not all
2887 blocks will be verified, if ``verify_backlog_batch`` is larger than
2888 :option:`verify_backlog`, some blocks will be verified more than once.
2890 .. option:: verify_state_save=bool
2892 When a job exits during the write phase of a verify workload, save its
2893 current state. This allows fio to replay up until that point, if the verify
2894 state is loaded for the verify read phase. The format of the filename is,
2897 <type>-<jobname>-<jobindex>-verify.state.
2899 <type> is "local" for a local run, "sock" for a client/server socket
2900 connection, and "ip" (192.168.0.1, for instance) for a networked
2901 client/server connection. Defaults to true.
2903 .. option:: verify_state_load=bool
2905 If a verify termination trigger was used, fio stores the current write state
2906 of each thread. This can be used at verification time so that fio knows how
2907 far it should verify. Without this information, fio will run a full
2908 verification pass, according to the settings in the job file used. Default
2911 .. option:: trim_percentage=int
2913 Number of verify blocks to discard/trim.
2915 .. option:: trim_verify_zero=bool
2917 Verify that trim/discarded blocks are returned as zeros.
2919 .. option:: trim_backlog=int
2921 Trim after this number of blocks are written.
2923 .. option:: trim_backlog_batch=int
2925 Trim this number of I/O blocks.
2927 .. option:: experimental_verify=bool
2929 Enable experimental verification.
2934 .. option:: steadystate=str:float, ss=str:float
2936 Define the criterion and limit for assessing steady state performance. The
2937 first parameter designates the criterion whereas the second parameter sets
2938 the threshold. When the criterion falls below the threshold for the
2939 specified duration, the job will stop. For example, `iops_slope:0.1%` will
2940 direct fio to terminate the job when the least squares regression slope
2941 falls below 0.1% of the mean IOPS. If :option:`group_reporting` is enabled
2942 this will apply to all jobs in the group. Below is the list of available
2943 steady state assessment criteria. All assessments are carried out using only
2944 data from the rolling collection window. Threshold limits can be expressed
2945 as a fixed value or as a percentage of the mean in the collection window.
2948 Collect IOPS data. Stop the job if all individual IOPS measurements
2949 are within the specified limit of the mean IOPS (e.g., ``iops:2``
2950 means that all individual IOPS values must be within 2 of the mean,
2951 whereas ``iops:0.2%`` means that all individual IOPS values must be
2952 within 0.2% of the mean IOPS to terminate the job).
2955 Collect IOPS data and calculate the least squares regression
2956 slope. Stop the job if the slope falls below the specified limit.
2959 Collect bandwidth data. Stop the job if all individual bandwidth
2960 measurements are within the specified limit of the mean bandwidth.
2963 Collect bandwidth data and calculate the least squares regression
2964 slope. Stop the job if the slope falls below the specified limit.
2966 .. option:: steadystate_duration=time, ss_dur=time
2968 A rolling window of this duration will be used to judge whether steady state
2969 has been reached. Data will be collected once per second. The default is 0
2970 which disables steady state detection. When the unit is omitted, the
2971 value is interpreted in seconds.
2973 .. option:: steadystate_ramp_time=time, ss_ramp=time
2975 Allow the job to run for the specified duration before beginning data
2976 collection for checking the steady state job termination criterion. The
2977 default is 0. When the unit is omitted, the value is interpreted in seconds.
2980 Measurements and reporting
2981 ~~~~~~~~~~~~~~~~~~~~~~~~~~
2983 .. option:: per_job_logs=bool
2985 If set, this generates bw/clat/iops log with per file private filenames. If
2986 not set, jobs with identical names will share the log filename. Default:
2989 .. option:: group_reporting
2991 It may sometimes be interesting to display statistics for groups of jobs as
2992 a whole instead of for each individual job. This is especially true if
2993 :option:`numjobs` is used; looking at individual thread/process output
2994 quickly becomes unwieldy. To see the final report per-group instead of
2995 per-job, use :option:`group_reporting`. Jobs in a file will be part of the
2996 same reporting group, unless if separated by a :option:`stonewall`, or by
2997 using :option:`new_group`.
2999 .. option:: new_group
3001 Start a new reporting group. See: :option:`group_reporting`. If not given,
3002 all jobs in a file will be part of the same reporting group, unless
3003 separated by a :option:`stonewall`.
3005 .. option:: stats=bool
3007 By default, fio collects and shows final output results for all jobs
3008 that run. If this option is set to 0, then fio will ignore it in
3009 the final stat output.
3011 .. option:: write_bw_log=str
3013 If given, write a bandwidth log for this job. Can be used to store data of
3014 the bandwidth of the jobs in their lifetime.
3016 If no str argument is given, the default filename of
3017 :file:`jobname_type.x.log` is used. Even when the argument is given, fio
3018 will still append the type of log. So if one specifies::
3022 The actual log name will be :file:`foo_bw.x.log` where `x` is the index
3023 of the job (`1..N`, where `N` is the number of jobs). If
3024 :option:`per_job_logs` is false, then the filename will not include the
3027 The included :command:`fio_generate_plots` script uses :command:`gnuplot` to turn these
3028 text files into nice graphs. See `Log File Formats`_ for how data is
3029 structured within the file.
3031 .. option:: write_lat_log=str
3033 Same as :option:`write_bw_log`, except this option creates I/O
3034 submission (e.g., :file:`name_slat.x.log`), completion (e.g.,
3035 :file:`name_clat.x.log`), and total (e.g., :file:`name_lat.x.log`)
3036 latency files instead. See :option:`write_bw_log` for details about
3037 the filename format and `Log File Formats`_ for how data is structured
3040 .. option:: write_hist_log=str
3042 Same as :option:`write_bw_log` but writes an I/O completion latency
3043 histogram file (e.g., :file:`name_hist.x.log`) instead. Note that this
3044 file will be empty unless :option:`log_hist_msec` has also been set.
3045 See :option:`write_bw_log` for details about the filename format and
3046 `Log File Formats`_ for how data is structured within the file.
3048 .. option:: write_iops_log=str
3050 Same as :option:`write_bw_log`, but writes an IOPS file (e.g.
3051 :file:`name_iops.x.log`) instead. Because fio defaults to individual
3052 I/O logging, the value entry in the IOPS log will be 1 unless windowed
3053 logging (see :option:`log_avg_msec`) has been enabled. See
3054 :option:`write_bw_log` for details about the filename format and `Log
3055 File Formats`_ for how data is structured within the file.
3057 .. option:: log_avg_msec=int
3059 By default, fio will log an entry in the iops, latency, or bw log for every
3060 I/O that completes. When writing to the disk log, that can quickly grow to a
3061 very large size. Setting this option makes fio average the each log entry
3062 over the specified period of time, reducing the resolution of the log. See
3063 :option:`log_max_value` as well. Defaults to 0, logging all entries.
3064 Also see `Log File Formats`_.
3066 .. option:: log_hist_msec=int
3068 Same as :option:`log_avg_msec`, but logs entries for completion latency
3069 histograms. Computing latency percentiles from averages of intervals using
3070 :option:`log_avg_msec` is inaccurate. Setting this option makes fio log
3071 histogram entries over the specified period of time, reducing log sizes for
3072 high IOPS devices while retaining percentile accuracy. See
3073 :option:`log_hist_coarseness` and :option:`write_hist_log` as well.
3074 Defaults to 0, meaning histogram logging is disabled.
3076 .. option:: log_hist_coarseness=int
3078 Integer ranging from 0 to 6, defining the coarseness of the resolution of
3079 the histogram logs enabled with :option:`log_hist_msec`. For each increment
3080 in coarseness, fio outputs half as many bins. Defaults to 0, for which
3081 histogram logs contain 1216 latency bins. See :option:`write_hist_log`
3082 and `Log File Formats`_.
3084 .. option:: log_max_value=bool
3086 If :option:`log_avg_msec` is set, fio logs the average over that window. If
3087 you instead want to log the maximum value, set this option to 1. Defaults to
3088 0, meaning that averaged values are logged.
3090 .. option:: log_offset=bool
3092 If this is set, the iolog options will include the byte offset for the I/O
3093 entry as well as the other data values. Defaults to 0 meaning that
3094 offsets are not present in logs. Also see `Log File Formats`_.
3096 .. option:: log_compression=int
3098 If this is set, fio will compress the I/O logs as it goes, to keep the
3099 memory footprint lower. When a log reaches the specified size, that chunk is
3100 removed and compressed in the background. Given that I/O logs are fairly
3101 highly compressible, this yields a nice memory savings for longer runs. The
3102 downside is that the compression will consume some background CPU cycles, so
3103 it may impact the run. This, however, is also true if the logging ends up
3104 consuming most of the system memory. So pick your poison. The I/O logs are
3105 saved normally at the end of a run, by decompressing the chunks and storing
3106 them in the specified log file. This feature depends on the availability of
3109 .. option:: log_compression_cpus=str
3111 Define the set of CPUs that are allowed to handle online log compression for
3112 the I/O jobs. This can provide better isolation between performance
3113 sensitive jobs, and background compression work. See
3114 :option:`cpus_allowed` for the format used.
3116 .. option:: log_store_compressed=bool
3118 If set, fio will store the log files in a compressed format. They can be
3119 decompressed with fio, using the :option:`--inflate-log` command line
3120 parameter. The files will be stored with a :file:`.fz` suffix.
3122 .. option:: log_unix_epoch=bool
3124 If set, fio will log Unix timestamps to the log files produced by enabling
3125 write_type_log for each log type, instead of the default zero-based
3128 .. option:: block_error_percentiles=bool
3130 If set, record errors in trim block-sized units from writes and trims and
3131 output a histogram of how many trims it took to get to errors, and what kind
3132 of error was encountered.
3134 .. option:: bwavgtime=int
3136 Average the calculated bandwidth over the given time. Value is specified in
3137 milliseconds. If the job also does bandwidth logging through
3138 :option:`write_bw_log`, then the minimum of this option and
3139 :option:`log_avg_msec` will be used. Default: 500ms.
3141 .. option:: iopsavgtime=int
3143 Average the calculated IOPS over the given time. Value is specified in
3144 milliseconds. If the job also does IOPS logging through
3145 :option:`write_iops_log`, then the minimum of this option and
3146 :option:`log_avg_msec` will be used. Default: 500ms.
3148 .. option:: disk_util=bool
3150 Generate disk utilization statistics, if the platform supports it.
3153 .. option:: disable_lat=bool
3155 Disable measurements of total latency numbers. Useful only for cutting back
3156 the number of calls to :manpage:`gettimeofday(2)`, as that does impact
3157 performance at really high IOPS rates. Note that to really get rid of a
3158 large amount of these calls, this option must be used with
3159 :option:`disable_slat` and :option:`disable_bw_measurement` as well.
3161 .. option:: disable_clat=bool
3163 Disable measurements of completion latency numbers. See
3164 :option:`disable_lat`.
3166 .. option:: disable_slat=bool
3168 Disable measurements of submission latency numbers. See
3169 :option:`disable_lat`.
3171 .. option:: disable_bw_measurement=bool, disable_bw=bool
3173 Disable measurements of throughput/bandwidth numbers. See
3174 :option:`disable_lat`.
3176 .. option:: clat_percentiles=bool
3178 Enable the reporting of percentiles of completion latencies. This
3179 option is mutually exclusive with :option:`lat_percentiles`.
3181 .. option:: lat_percentiles=bool
3183 Enable the reporting of percentiles of I/O latencies. This is similar
3184 to :option:`clat_percentiles`, except that this includes the
3185 submission latency. This option is mutually exclusive with
3186 :option:`clat_percentiles`.
3188 .. option:: percentile_list=float_list
3190 Overwrite the default list of percentiles for completion latencies and
3191 the block error histogram. Each number is a floating number in the
3192 range (0,100], and the maximum length of the list is 20. Use ``:`` to
3193 separate the numbers, and list the numbers in ascending order. For
3194 example, ``--percentile_list=99.5:99.9`` will cause fio to report the
3195 values of completion latency below which 99.5% and 99.9% of the observed
3196 latencies fell, respectively.
3198 .. option:: significant_figures=int
3200 If using :option:`--output-format` of `normal`, set the significant
3201 figures to this value. Higher values will yield more precise IOPS and
3202 throughput units, while lower values will round. Requires a minimum
3203 value of 1 and a maximum value of 10. Defaults to 4.
3209 .. option:: exitall_on_error
3211 When one job finishes in error, terminate the rest. The default is to wait
3212 for each job to finish.
3214 .. option:: continue_on_error=str
3216 Normally fio will exit the job on the first observed failure. If this option
3217 is set, fio will continue the job when there is a 'non-fatal error' (EIO or
3218 EILSEQ) until the runtime is exceeded or the I/O size specified is
3219 completed. If this option is used, there are two more stats that are
3220 appended, the total error count and the first error. The error field given
3221 in the stats is the first error that was hit during the run.
3223 The allowed values are:
3226 Exit on any I/O or verify errors.
3229 Continue on read errors, exit on all others.
3232 Continue on write errors, exit on all others.
3235 Continue on any I/O error, exit on all others.
3238 Continue on verify errors, exit on all others.
3241 Continue on all errors.
3244 Backward-compatible alias for 'none'.
3247 Backward-compatible alias for 'all'.
3249 .. option:: ignore_error=str
3251 Sometimes you want to ignore some errors during test in that case you can
3252 specify error list for each error type, instead of only being able to
3253 ignore the default 'non-fatal error' using :option:`continue_on_error`.
3254 ``ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST`` errors for
3255 given error type is separated with ':'. Error may be symbol ('ENOSPC',
3256 'ENOMEM') or integer. Example::
3258 ignore_error=EAGAIN,ENOSPC:122
3260 This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from
3261 WRITE. This option works by overriding :option:`continue_on_error` with
3262 the list of errors for each error type if any.
3264 .. option:: error_dump=bool
3266 If set dump every error even if it is non fatal, true by default. If
3267 disabled only fatal error will be dumped.
3269 Running predefined workloads
3270 ----------------------------
3272 Fio includes predefined profiles that mimic the I/O workloads generated by
3275 .. option:: profile=str
3277 The predefined workload to run. Current profiles are:
3280 Threaded I/O bench (tiotest/tiobench) like workload.
3283 Aerospike Certification Tool (ACT) like workload.
3285 To view a profile's additional options use :option:`--cmdhelp` after specifying
3286 the profile. For example::
3288 $ fio --profile=act --cmdhelp
3293 .. option:: device-names=str
3298 .. option:: load=int
3301 ACT load multiplier. Default: 1.
3303 .. option:: test-duration=time
3306 How long the entire test takes to run. When the unit is omitted, the value
3307 is given in seconds. Default: 24h.
3309 .. option:: threads-per-queue=int
3312 Number of read I/O threads per device. Default: 8.
3314 .. option:: read-req-num-512-blocks=int
3317 Number of 512B blocks to read at the time. Default: 3.
3319 .. option:: large-block-op-kbytes=int
3322 Size of large block ops in KiB (writes). Default: 131072.
3327 Set to run ACT prep phase.
3329 Tiobench profile options
3330 ~~~~~~~~~~~~~~~~~~~~~~~~
3332 .. option:: size=str
3337 .. option:: block=int
3340 Block size in bytes. Default: 4096.
3342 .. option:: numruns=int
3352 .. option:: threads=int
3357 Interpreting the output
3358 -----------------------
3361 Example output was based on the following:
3362 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --time_based \
3363 --rate=1256k --bs=14K --name=quick --runtime=1s --name=mixed \
3364 --runtime=2m --rw=rw
3366 Fio spits out a lot of output. While running, fio will display the status of the
3367 jobs created. An example of that would be::
3369 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]
3371 The characters inside the first set of square brackets denote the current status of
3372 each thread. The first character is the first job defined in the job file, and so
3373 forth. The possible values (in typical life cycle order) are:
3375 +------+-----+-----------------------------------------------------------+
3377 +======+=====+===========================================================+
3378 | P | | Thread setup, but not started. |
3379 +------+-----+-----------------------------------------------------------+
3380 | C | | Thread created. |
3381 +------+-----+-----------------------------------------------------------+
3382 | I | | Thread initialized, waiting or generating necessary data. |
3383 +------+-----+-----------------------------------------------------------+
3384 | | p | Thread running pre-reading file(s). |
3385 +------+-----+-----------------------------------------------------------+
3386 | | / | Thread is in ramp period. |
3387 +------+-----+-----------------------------------------------------------+
3388 | | R | Running, doing sequential reads. |
3389 +------+-----+-----------------------------------------------------------+
3390 | | r | Running, doing random reads. |
3391 +------+-----+-----------------------------------------------------------+
3392 | | W | Running, doing sequential writes. |
3393 +------+-----+-----------------------------------------------------------+
3394 | | w | Running, doing random writes. |
3395 +------+-----+-----------------------------------------------------------+
3396 | | M | Running, doing mixed sequential reads/writes. |
3397 +------+-----+-----------------------------------------------------------+
3398 | | m | Running, doing mixed random reads/writes. |
3399 +------+-----+-----------------------------------------------------------+
3400 | | D | Running, doing sequential trims. |
3401 +------+-----+-----------------------------------------------------------+
3402 | | d | Running, doing random trims. |
3403 +------+-----+-----------------------------------------------------------+
3404 | | F | Running, currently waiting for :manpage:`fsync(2)`. |
3405 +------+-----+-----------------------------------------------------------+
3406 | | V | Running, doing verification of written data. |
3407 +------+-----+-----------------------------------------------------------+
3408 | f | | Thread finishing. |
3409 +------+-----+-----------------------------------------------------------+
3410 | E | | Thread exited, not reaped by main thread yet. |
3411 +------+-----+-----------------------------------------------------------+
3412 | _ | | Thread reaped. |
3413 +------+-----+-----------------------------------------------------------+
3414 | X | | Thread reaped, exited with an error. |
3415 +------+-----+-----------------------------------------------------------+
3416 | K | | Thread reaped, exited due to signal. |
3417 +------+-----+-----------------------------------------------------------+
3420 Example output was based on the following:
3421 TZ=UTC fio --iodepth=8 --ioengine=null --size=100M --runtime=58m \
3422 --time_based --rate=2512k --bs=256K --numjobs=10 \
3423 --name=readers --rw=read --name=writers --rw=write
3425 Fio will condense the thread string as not to take up more space on the command
3426 line than needed. For instance, if you have 10 readers and 10 writers running,
3427 the output would look like this::
3429 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]
3431 Note that the status string is displayed in order, so it's possible to tell which of
3432 the jobs are currently doing what. In the example above this means that jobs 1--10
3433 are readers and 11--20 are writers.
3435 The other values are fairly self explanatory -- number of threads currently
3436 running and doing I/O, the number of currently open files (f=), the estimated
3437 completion percentage, the rate of I/O since last check (read speed listed first,
3438 then write speed and optionally trim speed) in terms of bandwidth and IOPS,
3439 and time to completion for the current running group. It's impossible to estimate
3440 runtime of the following groups (if any).
3443 Example output was based on the following:
3444 TZ=UTC fio --iodepth=16 --ioengine=posixaio --filename=/tmp/fiofile \
3445 --direct=1 --size=100M --time_based --runtime=50s --rate_iops=89 \
3446 --bs=7K --name=Client1 --rw=write
3448 When fio is done (or interrupted by :kbd:`Ctrl-C`), it will show the data for
3449 each thread, group of threads, and disks in that order. For each overall thread (or
3450 group) the output looks like::
3452 Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
3453 write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
3454 slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
3455 clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
3456 lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
3457 clat percentiles (usec):
3458 | 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
3459 | 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
3460 | 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
3461 | 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
3463 bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
3464 iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
3465 lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
3466 lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
3467 lat (msec) : 100=0.65%
3468 cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
3469 IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
3470 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
3471 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
3472 issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
3473 latency : target=0, window=0, percentile=100.00%, depth=8
3475 The job name (or first job's name when using :option:`group_reporting`) is printed,
3476 along with the group id, count of jobs being aggregated, last error id seen (which
3477 is 0 when there are no errors), pid/tid of that thread and the time the job/group
3478 completed. Below are the I/O statistics for each data direction performed (showing
3479 writes in the example above). In the order listed, they denote:
3482 The string before the colon shows the I/O direction the statistics
3483 are for. **IOPS** is the average I/Os performed per second. **BW**
3484 is the average bandwidth rate shown as: value in power of 2 format
3485 (value in power of 10 format). The last two values show: (**total
3486 I/O performed** in power of 2 format / **runtime** of that thread).
3489 Submission latency (**min** being the minimum, **max** being the
3490 maximum, **avg** being the average, **stdev** being the standard
3491 deviation). This is the time it took to submit the I/O. For
3492 sync I/O this row is not displayed as the slat is really the
3493 completion latency (since queue/complete is one operation there).
3494 This value can be in nanoseconds, microseconds or milliseconds ---
3495 fio will choose the most appropriate base and print that (in the
3496 example above nanoseconds was the best scale). Note: in :option:`--minimal` mode
3497 latencies are always expressed in microseconds.
3500 Completion latency. Same names as slat, this denotes the time from
3501 submission to completion of the I/O pieces. For sync I/O, clat will
3502 usually be equal (or very close) to 0, as the time from submit to
3503 complete is basically just CPU time (I/O has already been done, see slat
3507 Total latency. Same names as slat and clat, this denotes the time from
3508 when fio created the I/O unit to completion of the I/O operation.
3511 Bandwidth statistics based on samples. Same names as the xlat stats,
3512 but also includes the number of samples taken (**samples**) and an
3513 approximate percentage of total aggregate bandwidth this thread
3514 received in its group (**per**). This last value is only really
3515 useful if the threads in this group are on the same disk, since they
3516 are then competing for disk access.
3519 IOPS statistics based on samples. Same names as bw.
3521 **lat (nsec/usec/msec)**
3522 The distribution of I/O completion latencies. This is the time from when
3523 I/O leaves fio and when it gets completed. Unlike the separate
3524 read/write/trim sections above, the data here and in the remaining
3525 sections apply to all I/Os for the reporting group. 250=0.04% means that
3526 0.04% of the I/Os completed in under 250us. 500=64.11% means that 64.11%
3527 of the I/Os required 250 to 499us for completion.
3530 CPU usage. User and system time, along with the number of context
3531 switches this thread went through, usage of system and user time, and
3532 finally the number of major and minor page faults. The CPU utilization
3533 numbers are averages for the jobs in that reporting group, while the
3534 context and fault counters are summed.
3537 The distribution of I/O depths over the job lifetime. The numbers are
3538 divided into powers of 2 and each entry covers depths from that value
3539 up to those that are lower than the next entry -- e.g., 16= covers
3540 depths from 16 to 31. Note that the range covered by a depth
3541 distribution entry can be different to the range covered by the
3542 equivalent submit/complete distribution entry.
3545 How many pieces of I/O were submitting in a single submit call. Each
3546 entry denotes that amount and below, until the previous entry -- e.g.,
3547 16=100% means that we submitted anywhere between 9 to 16 I/Os per submit
3548 call. Note that the range covered by a submit distribution entry can
3549 be different to the range covered by the equivalent depth distribution
3553 Like the above submit number, but for completions instead.
3556 The number of read/write/trim requests issued, and how many of them were
3560 These values are for :option:`latency_target` and related options. When
3561 these options are engaged, this section describes the I/O depth required
3562 to meet the specified latency target.
3565 Example output was based on the following:
3566 TZ=UTC fio --ioengine=null --iodepth=2 --size=100M --numjobs=2 \
3567 --rate_process=poisson --io_limit=32M --name=read --bs=128k \
3568 --rate=11M --name=write --rw=write --bs=2k --rate=700k
3570 After each client has been listed, the group statistics are printed. They
3571 will look like this::
3573 Run status group 0 (all jobs):
3574 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
3575 WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
3577 For each data direction it prints:
3580 Aggregate bandwidth of threads in this group followed by the
3581 minimum and maximum bandwidth of all the threads in this group.
3582 Values outside of brackets are power-of-2 format and those
3583 within are the equivalent value in a power-of-10 format.
3585 Aggregate I/O performed of all threads in this group. The
3586 format is the same as bw.
3588 The smallest and longest runtimes of the threads in this group.
3590 And finally, the disk statistics are printed. This is Linux specific. They will look like this::
3592 Disk stats (read/write):
3593 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
3595 Each value is printed for both reads and writes, with reads first. The
3599 Number of I/Os performed by all groups.
3601 Number of merges performed by the I/O scheduler.
3603 Number of ticks we kept the disk busy.
3605 Total time spent in the disk queue.
3607 The disk utilization. A value of 100% means we kept the disk
3608 busy constantly, 50% would be a disk idling half of the time.
3610 It is also possible to get fio to dump the current output while it is running,
3611 without terminating the job. To do that, send fio the **USR1** signal. You can
3612 also get regularly timed dumps by using the :option:`--status-interval`
3613 parameter, or by creating a file in :file:`/tmp` named
3614 :file:`fio-dump-status`. If fio sees this file, it will unlink it and dump the
3615 current output status.
3621 For scripted usage where you typically want to generate tables or graphs of the
3622 results, fio can output the results in a semicolon separated format. The format
3623 is one long line of values, such as::
3625 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%
3626 A description of this job goes here.
3628 The job description (if provided) follows on a second line.
3630 To enable terse output, use the :option:`--minimal` or
3631 :option:`--output-format`\=terse command line options. The
3632 first value is the version of the terse output format. If the output has to be
3633 changed for some reason, this number will be incremented by 1 to signify that
3636 Split up, the format is as follows (comments in brackets denote when a
3637 field was introduced or whether it's specific to some terse version):
3641 terse version, fio version [v3], jobname, groupid, error
3645 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
3646 Submission latency: min, max, mean, stdev (usec)
3647 Completion latency: min, max, mean, stdev (usec)
3648 Completion latency percentiles: 20 fields (see below)
3649 Total latency: min, max, mean, stdev (usec)
3650 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
3651 IOPS [v5]: min, max, mean, stdev, number of samples
3657 Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
3658 Submission latency: min, max, mean, stdev (usec)
3659 Completion latency: min, max, mean, stdev (usec)
3660 Completion latency percentiles: 20 fields (see below)
3661 Total latency: min, max, mean, stdev (usec)
3662 Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
3663 IOPS [v5]: min, max, mean, stdev, number of samples
3665 TRIM status [all but version 3]:
3667 Fields are similar to READ/WRITE status.
3671 user, system, context switches, major faults, minor faults
3675 <=1, 2, 4, 8, 16, 32, >=64
3677 I/O latencies microseconds::
3679 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
3681 I/O latencies milliseconds::
3683 <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
3685 Disk utilization [v3]::
3687 disk name, read ios, write ios, read merges, write merges, read ticks, write ticks,
3688 time spent in queue, disk utilization percentage
3690 Additional Info (dependent on continue_on_error, default off)::
3692 total # errors, first error code
3694 Additional Info (dependent on description being set)::
3698 Completion latency percentiles can be a grouping of up to 20 sets, so for the
3699 terse output fio writes all of them. Each field will look like this::
3703 which is the Xth percentile, and the `usec` latency associated with it.
3705 For `Disk utilization`, all disks used by fio are shown. So for each disk there
3706 will be a disk utilization section.
3708 Below is a single line containing short names for each of the fields in the
3709 minimal output v3, separated by semicolons::
3711 terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth;read_iops;read_runtime_ms;read_slat_min;read_slat_max;read_slat_mean;read_slat_dev;read_clat_min;read_clat_max;read_clat_mean;read_clat_dev;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min;read_lat_max;read_lat_mean;read_lat_dev;read_bw_min;read_bw_max;read_bw_agg_pct;read_bw_mean;read_bw_dev;write_kb;write_bandwidth;write_iops;write_runtime_ms;write_slat_min;write_slat_max;write_slat_mean;write_slat_dev;write_clat_min;write_clat_max;write_clat_mean;write_clat_dev;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min;write_lat_max;write_lat_mean;write_lat_dev;write_bw_min;write_bw_max;write_bw_agg_pct;write_bw_mean;write_bw_dev;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
3717 The `json` output format is intended to be both human readable and convenient
3718 for automated parsing. For the most part its sections mirror those of the
3719 `normal` output. The `runtime` value is reported in msec and the `bw` value is
3720 reported in 1024 bytes per second units.
3726 The `json+` output format is identical to the `json` output format except that it
3727 adds a full dump of the completion latency bins. Each `bins` object contains a
3728 set of (key, value) pairs where keys are latency durations and values count how
3729 many I/Os had completion latencies of the corresponding duration. For example,
3732 "bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840" : 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529, ... }
3734 This data indicates that one I/O required 87,552ns to complete, two I/Os required
3735 100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
3737 Also included with fio is a Python script `fio_jsonplus_clat2csv` that takes
3738 json+ output and generates CSV-formatted latency data suitable for plotting.
3740 The latency durations actually represent the midpoints of latency intervals.
3741 For details refer to :file:`stat.h`.
3747 There are two trace file format that you can encounter. The older (v1) format is
3748 unsupported since version 1.20-rc3 (March 2008). It will still be described
3749 below in case that you get an old trace and want to understand it.
3751 In any case the trace is a simple text file with a single action per line.
3754 Trace file format v1
3755 ~~~~~~~~~~~~~~~~~~~~
3757 Each line represents a single I/O action in the following format::
3761 where `rw=0/1` for read/write, and the `offset` and `length` entries being in bytes.
3763 This format is not supported in fio versions >= 1.20-rc3.
3766 Trace file format v2
3767 ~~~~~~~~~~~~~~~~~~~~
3769 The second version of the trace file format was added in fio version 1.17. It
3770 allows to access more then one file per trace and has a bigger set of possible
3773 The first line of the trace file has to be::
3777 Following this can be lines in two different formats, which are described below.
3779 The file management format::
3783 The `filename` is given as an absolute path. The `action` can be one of these:
3786 Add the given `filename` to the trace.
3788 Open the file with the given `filename`. The `filename` has to have
3789 been added with the **add** action before.
3791 Close the file with the given `filename`. The file has to have been
3795 The file I/O action format::
3797 filename action offset length
3799 The `filename` is given as an absolute path, and has to have been added and
3800 opened before it can be used with this format. The `offset` and `length` are
3801 given in bytes. The `action` can be one of these:
3804 Wait for `offset` microseconds. Everything below 100 is discarded.
3805 The time is relative to the previous `wait` statement.
3807 Read `length` bytes beginning from `offset`.
3809 Write `length` bytes beginning from `offset`.
3811 :manpage:`fsync(2)` the file.
3813 :manpage:`fdatasync(2)` the file.
3815 Trim the given file from the given `offset` for `length` bytes.
3817 CPU idleness profiling
3818 ----------------------
3820 In some cases, we want to understand CPU overhead in a test. For example, we
3821 test patches for the specific goodness of whether they reduce CPU usage.
3822 Fio implements a balloon approach to create a thread per CPU that runs at idle
3823 priority, meaning that it only runs when nobody else needs the cpu.
3824 By measuring the amount of work completed by the thread, idleness of each CPU
3825 can be derived accordingly.
3827 An unit work is defined as touching a full page of unsigned characters. Mean and
3828 standard deviation of time to complete an unit work is reported in "unit work"
3829 section. Options can be chosen to report detailed percpu idleness or overall
3830 system idleness by aggregating percpu stats.
3833 Verification and triggers
3834 -------------------------
3836 Fio is usually run in one of two ways, when data verification is done. The first
3837 is a normal write job of some sort with verify enabled. When the write phase has
3838 completed, fio switches to reads and verifies everything it wrote. The second
3839 model is running just the write phase, and then later on running the same job
3840 (but with reads instead of writes) to repeat the same I/O patterns and verify
3841 the contents. Both of these methods depend on the write phase being completed,
3842 as fio otherwise has no idea how much data was written.
3844 With verification triggers, fio supports dumping the current write state to
3845 local files. Then a subsequent read verify workload can load this state and know
3846 exactly where to stop. This is useful for testing cases where power is cut to a
3847 server in a managed fashion, for instance.
3849 A verification trigger consists of two things:
3851 1) Storing the write state of each job.
3852 2) Executing a trigger command.
3854 The write state is relatively small, on the order of hundreds of bytes to single
3855 kilobytes. It contains information on the number of completions done, the last X
3858 A trigger is invoked either through creation ('touch') of a specified file in
3859 the system, or through a timeout setting. If fio is run with
3860 :option:`--trigger-file`\= :file:`/tmp/trigger-file`, then it will continually
3861 check for the existence of :file:`/tmp/trigger-file`. When it sees this file, it
3862 will fire off the trigger (thus saving state, and executing the trigger
3865 For client/server runs, there's both a local and remote trigger. If fio is
3866 running as a server backend, it will send the job states back to the client for
3867 safe storage, then execute the remote trigger, if specified. If a local trigger
3868 is specified, the server will still send back the write state, but the client
3869 will then execute the trigger.
3871 Verification trigger example
3872 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3874 Let's say we want to run a powercut test on the remote Linux machine 'server'.
3875 Our write workload is in :file:`write-test.fio`. We want to cut power to 'server' at
3876 some point during the run, and we'll run this test from the safety or our local
3877 machine, 'localbox'. On the server, we'll start the fio backend normally::
3879 server# fio --server
3881 and on the client, we'll fire off the workload::
3883 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
3885 We set :file:`/tmp/my-trigger` as the trigger file, and we tell fio to execute::
3887 echo b > /proc/sysrq-trigger
3889 on the server once it has received the trigger and sent us the write state. This
3890 will work, but it's not **really** cutting power to the server, it's merely
3891 abruptly rebooting it. If we have a remote way of cutting power to the server
3892 through IPMI or similar, we could do that through a local trigger command
3893 instead. Let's assume we have a script that does IPMI reboot of a given hostname,
3894 ipmi-reboot. On localbox, we could then have run fio with a local trigger
3897 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
3899 For this case, fio would wait for the server to send us the write state, then
3900 execute ``ipmi-reboot server`` when that happened.
3902 Loading verify state
3903 ~~~~~~~~~~~~~~~~~~~~
3905 To load stored write state, a read verification job file must contain the
3906 :option:`verify_state_load` option. If that is set, fio will load the previously
3907 stored state. For a local fio run this is done by loading the files directly,
3908 and on a client/server run, the server backend will ask the client to send the
3909 files over and load them from there.
3915 Fio supports a variety of log file formats, for logging latencies, bandwidth,
3916 and IOPS. The logs share a common format, which looks like this:
3918 *time* (`msec`), *value*, *data direction*, *block size* (`bytes`),
3921 *Time* for the log entry is always in milliseconds. The *value* logged depends
3922 on the type of log, it will be one of the following:
3925 Value is latency in nsecs
3931 *Data direction* is one of the following:
3940 The entry's *block size* is always in bytes. The *offset* is the position in bytes
3941 from the start of the file for that particular I/O. The logging of the offset can be
3942 toggled with :option:`log_offset`.
3944 Fio defaults to logging every individual I/O but when windowed logging is set
3945 through :option:`log_avg_msec`, either the average (by default) or the maximum
3946 (:option:`log_max_value` is set) *value* seen over the specified period of time
3947 is recorded. Each *data direction* seen within the window period will aggregate
3948 its values in a separate row. Further, when using windowed logging the *block
3949 size* and *offset* entries will always contain 0.
3954 Normally fio is invoked as a stand-alone application on the machine where the
3955 I/O workload should be generated. However, the backend and frontend of fio can
3956 be run separately i.e., the fio server can generate an I/O workload on the "Device
3957 Under Test" while being controlled by a client on another machine.
3959 Start the server on the machine which has access to the storage DUT::
3963 where `args` defines what fio listens to. The arguments are of the form
3964 ``type,hostname`` or ``IP,port``. *type* is either ``ip`` (or ip4) for TCP/IP
3965 v4, ``ip6`` for TCP/IP v6, or ``sock`` for a local unix domain socket.
3966 *hostname* is either a hostname or IP address, and *port* is the port to listen
3967 to (only valid for TCP/IP, not a local socket). Some examples:
3971 Start a fio server, listening on all interfaces on the default port (8765).
3973 2) ``fio --server=ip:hostname,4444``
3975 Start a fio server, listening on IP belonging to hostname and on port 4444.
3977 3) ``fio --server=ip6:::1,4444``
3979 Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
3981 4) ``fio --server=,4444``
3983 Start a fio server, listening on all interfaces on port 4444.
3985 5) ``fio --server=1.2.3.4``
3987 Start a fio server, listening on IP 1.2.3.4 on the default port.
3989 6) ``fio --server=sock:/tmp/fio.sock``
3991 Start a fio server, listening on the local socket :file:`/tmp/fio.sock`.
3993 Once a server is running, a "client" can connect to the fio server with::
3995 fio <local-args> --client=<server> <remote-args> <job file(s)>
3997 where `local-args` are arguments for the client where it is running, `server`
3998 is the connect string, and `remote-args` and `job file(s)` are sent to the
3999 server. The `server` string follows the same format as it does on the server
4000 side, to allow IP/hostname/socket and port strings.
4002 Fio can connect to multiple servers this way::
4004 fio --client=<server1> <job file(s)> --client=<server2> <job file(s)>
4006 If the job file is located on the fio server, then you can tell the server to
4007 load a local file as well. This is done by using :option:`--remote-config` ::
4009 fio --client=server --remote-config /path/to/file.fio
4011 Then fio will open this local (to the server) job file instead of being passed
4012 one from the client.
4014 If you have many servers (example: 100 VMs/containers), you can input a pathname
4015 of a file containing host IPs/names as the parameter value for the
4016 :option:`--client` option. For example, here is an example :file:`host.list`
4017 file containing 2 hostnames::
4019 host1.your.dns.domain
4020 host2.your.dns.domain
4022 The fio command would then be::
4024 fio --client=host.list <job file(s)>
4026 In this mode, you cannot input server-specific parameters or job files -- all
4027 servers receive the same job file.
4029 In order to let ``fio --client`` runs use a shared filesystem from multiple
4030 hosts, ``fio --client`` now prepends the IP address of the server to the
4031 filename. For example, if fio is using the directory :file:`/mnt/nfs/fio` and is
4032 writing filename :file:`fileio.tmp`, with a :option:`--client` `hostfile`
4033 containing two hostnames ``h1`` and ``h2`` with IP addresses 192.168.10.120 and
4034 192.168.10.121, then fio will create two files::
4036 /mnt/nfs/fio/192.168.10.120.fileio.tmp
4037 /mnt/nfs/fio/192.168.10.121.fileio.tmp