8 5. Detailed list of parameters
12 9. CPU idleness profiling
14 1.0 Overview and history
15 ------------------------
16 fio was originally written to save me the hassle of writing special test
17 case programs when I wanted to test a specific workload, either for
18 performance reasons or to find/reproduce a bug. The process of writing
19 such a test app can be tiresome, especially if you have to do it often.
20 Hence I needed a tool that would be able to simulate a given io workload
21 without resorting to writing a tailored test case again and again.
23 A test work load is difficult to define, though. There can be any number
24 of processes or threads involved, and they can each be using their own
25 way of generating io. You could have someone dirtying large amounts of
26 memory in an memory mapped file, or maybe several threads issuing
27 reads using asynchronous io. fio needed to be flexible enough to
28 simulate both of these cases, and many more.
32 The first step in getting fio to simulate a desired io workload, is
33 writing a job file describing that specific setup. A job file may contain
34 any number of threads and/or files - the typical contents of the job file
35 is a global section defining shared parameters, and one or more job
36 sections describing the jobs involved. When run, fio parses this file
37 and sets everything up as described. If we break down a job from top to
38 bottom, it contains the following basic parameters:
40 IO type Defines the io pattern issued to the file(s).
41 We may only be reading sequentially from this
42 file(s), or we may be writing randomly. Or even
43 mixing reads and writes, sequentially or randomly.
45 Block size In how large chunks are we issuing io? This may be
46 a single value, or it may describe a range of
49 IO size How much data are we going to be reading/writing.
51 IO engine How do we issue io? We could be memory mapping the
52 file, we could be using regular read/write, we
53 could be using splice, async io, syslet, or even
56 IO depth If the io engine is async, how large a queuing
57 depth do we want to maintain?
59 IO type Should we be doing buffered io, or direct/raw io?
61 Num files How many files are we spreading the workload over.
63 Num threads How many threads or processes should we spread
66 The above are the basic parameters defined for a workload, in addition
67 there's a multitude of parameters that modify other aspects of how this
73 See the README file for command line parameters, there are only a few
76 Running fio is normally the easiest part - you just give it the job file
77 (or job files) as parameters:
81 and it will start doing what the job_file tells it to do. You can give
82 more than one job file on the command line, fio will serialize the running
83 of those files. Internally that is the same as using the 'stonewall'
84 parameter described in the parameter section.
86 If the job file contains only one job, you may as well just give the
87 parameters on the command line. The command line parameters are identical
88 to the job parameters, with a few extra that control global parameters
89 (see README). For example, for the job file parameter iodepth=2, the
90 mirror command line option would be --iodepth 2 or --iodepth=2. You can
91 also use the command line for giving more than one job entry. For each
92 --name option that fio sees, it will start a new job with that name.
93 Command line entries following a --name entry will apply to that job,
94 until there are no more entries or a new --name entry is seen. This is
95 similar to the job file options, where each option applies to the current
96 job until a new [] job entry is seen.
98 fio does not need to run as root, except if the files or devices specified
99 in the job section requires that. Some other options may also be restricted,
100 such as memory locking, io scheduler switching, and decreasing the nice value.
105 As previously described, fio accepts one or more job files describing
106 what it is supposed to do. The job file format is the classic ini file,
107 where the names enclosed in [] brackets define the job name. You are free
108 to use any ascii name you want, except 'global' which has special meaning.
109 A global section sets defaults for the jobs described in that file. A job
110 may override a global section parameter, and a job file may even have
111 several global sections if so desired. A job is only affected by a global
112 section residing above it. If the first character in a line is a ';' or a
113 '#', the entire line is discarded as a comment.
115 So let's look at a really simple job file that defines two processes, each
116 randomly reading from a 128MB file.
118 ; -- start job file --
129 As you can see, the job file sections themselves are empty as all the
130 described parameters are shared. As no filename= option is given, fio
131 makes up a filename for each of the jobs as it sees fit. On the command
132 line, this job would look as follows:
134 $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2
137 Let's look at an example that has a number of processes writing randomly
140 ; -- start job file --
152 Here we have no global section, as we only have one job defined anyway.
153 We want to use async io here, with a depth of 4 for each file. We also
154 increased the buffer size used to 32KB and define numjobs to 4 to
155 fork 4 identical jobs. The result is 4 processes each randomly writing
156 to their own 64MB file. Instead of using the above job file, you could
157 have given the parameters on the command line. For this case, you would
160 $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4
162 When fio is utilized as a basis of any reasonably large test suite, it might be
163 desirable to share a set of standardized settings across multiple job files.
164 Instead of copy/pasting such settings, any section may pull in an external
165 .fio file with 'include filename' directive, as in the following example:
167 ; -- start job file including.fio --
171 include glob-include.fio
178 include test-include.fio
179 ; -- end job file including.fio --
181 ; -- start job file glob-include.fio --
184 ; -- end job file glob-include.fio --
186 ; -- start job file test-include.fio --
189 ; -- end job file test-include.fio --
191 Settings pulled into a section apply to that section only (except global
192 section). Include directives may be nested in that any included file may
193 contain further include directive(s). Include files may not contain []
197 4.1 Environment variables
198 -------------------------
200 fio also supports environment variable expansion in job files. Any
201 sub-string of the form "${VARNAME}" as part of an option value (in other
202 words, on the right of the `='), will be expanded to the value of the
203 environment variable called VARNAME. If no such environment variable
204 is defined, or VARNAME is the empty string, the empty string will be
207 As an example, let's look at a sample fio invocation and job file:
209 $ SIZE=64m NUMJOBS=4 fio jobfile.fio
211 ; -- start job file --
218 This will expand to the following equivalent job file at runtime:
220 ; -- start job file --
227 fio ships with a few example job files, you can also look there for
230 4.2 Reserved keywords
231 ---------------------
233 Additionally, fio has a set of reserved keywords that will be replaced
234 internally with the appropriate value. Those keywords are:
236 $pagesize The architecture page size of the running system
237 $mb_memory Megabytes of total memory in the system
238 $ncpus Number of online available CPUs
240 These can be used on the command line or in the job file, and will be
241 automatically substituted with the current system values when the job
242 is run. Simple math is also supported on these keywords, so you can
243 perform actions like:
247 and get that properly expanded to 8 times the size of memory in the
251 5.0 Detailed list of parameters
252 -------------------------------
254 This section describes in details each parameter associated with a job.
255 Some parameters take an option of a given type, such as an integer or
256 a string. Anywhere a numeric value is required, an arithmetic expression
257 may be used, provided it is surrounded by parentheses. Supported operators
267 For time values in expressions, units are microseconds by default. This is
268 different than for time values not in expressions (not enclosed in
269 parentheses). The following types are used:
271 str String. This is a sequence of alpha characters.
272 time Integer with possible time suffix. In seconds unless otherwise
273 specified, use eg 10m for 10 minutes. Accepts s/m/h for seconds,
274 minutes, and hours, and accepts 'ms' (or 'msec') for milliseconds,
275 and 'us' (or 'usec') for microseconds.
276 int SI integer. A whole number value, which may contain a suffix
277 describing the base of the number. Accepted suffixes are k/m/g/t/p,
278 meaning kilo, mega, giga, tera, and peta. The suffix is not case
279 sensitive, and you may also include trailing 'b' (eg 'kb' is the same
280 as 'k'). So if you want to specify 4096, you could either write
281 out '4096' or just give 4k. The suffixes signify base 2 values, so
282 1024 is 1k and 1024k is 1m and so on, unless the suffix is explicitly
283 set to a base 10 value using 'kib', 'mib', 'gib', etc. If that is the
284 case, then 1000 is used as the multiplier. This can be handy for
285 disks, since manufacturers generally use base 10 values when listing
286 the capacity of a drive. If the option accepts an upper and lower
287 range, use a colon ':' or minus '-' to separate such values. May also
288 include a prefix to indicate numbers base. If 0x is used, the number
289 is assumed to be hexadecimal. See irange.
290 bool Boolean. Usually parsed as an integer, however only defined for
291 true and false (1 and 0).
292 irange Integer range with suffix. Allows value range to be given, such
293 as 1024-4096. A colon may also be used as the separator, eg
294 1k:4k. If the option allows two sets of ranges, they can be
295 specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see
297 float_list A list of floating numbers, separated by a ':' character.
299 With the above in mind, here follows the complete list of fio job
302 name=str ASCII name of the job. This may be used to override the
303 name printed by fio for this job. Otherwise the job
304 name is used. On the command line this parameter has the
305 special purpose of also signaling the start of a new
308 description=str Text description of the job. Doesn't do anything except
309 dump this text description when this job is run. It's
312 directory=str Prefix filenames with this directory. Used to place files
313 in a different location than "./". See the 'filename' option
314 for escaping certain characters.
316 filename=str Fio normally makes up a filename based on the job name,
317 thread number, and file number. If you want to share
318 files between threads in a job or several jobs, specify
319 a filename for each of them to override the default. If
320 the ioengine used is 'net', the filename is the host, port,
321 and protocol to use in the format of =host,port,protocol.
322 See ioengine=net for more. If the ioengine is file based, you
323 can specify a number of files by separating the names with a
324 ':' colon. So if you wanted a job to open /dev/sda and /dev/sdb
325 as the two working files, you would use
326 filename=/dev/sda:/dev/sdb. On Windows, disk devices are
327 accessed as \\.\PhysicalDrive0 for the first device,
328 \\.\PhysicalDrive1 for the second etc. Note: Windows and
329 FreeBSD prevent write access to areas of the disk containing
330 in-use data (e.g. filesystems).
331 If the wanted filename does need to include a colon, then
332 escape that with a '\' character. For instance, if the filename
333 is "/dev/dsk/foo@3,0:c", then you would use
334 filename="/dev/dsk/foo@3,0\:c". '-' is a reserved name, meaning
335 stdin or stdout. Which of the two depends on the read/write
339 If sharing multiple files between jobs, it is usually necessary
340 to have fio generate the exact names that you want. By default,
341 fio will name a file based on the default file format
342 specification of jobname.jobnumber.filenumber. With this
343 option, that can be customized. Fio will recognize and replace
344 the following keywords in this string:
347 The name of the worker thread or process.
350 The incremental number of the worker thread or
354 The incremental number of the file for that worker
357 To have dependent jobs share a set of files, this option can
358 be set to have fio generate filenames that are shared between
359 the two. For instance, if testfiles.$filenum is specified,
360 file number 4 for any job will be named testfiles.4. The
361 default of $jobname.$jobnum.$filenum will be used if
362 no other format specifier is given.
364 opendir=str Tell fio to recursively add any file it can find in this
365 directory and down the file system tree.
367 lockfile=str Fio defaults to not locking any files before it does
368 IO to them. If a file or file descriptor is shared, fio
369 can serialize IO to that file to make the end result
370 consistent. This is usual for emulating real workloads that
371 share files. The lock modes are:
373 none No locking. The default.
374 exclusive Only one thread/process may do IO,
375 excluding all others.
376 readwrite Read-write locking on the file. Many
377 readers may access the file at the
378 same time, but writes get exclusive
382 rw=str Type of io pattern. Accepted values are:
384 read Sequential reads
385 write Sequential writes
386 randwrite Random writes
387 randread Random reads
388 rw,readwrite Sequential mixed reads and writes
389 randrw Random mixed reads and writes
390 trimwrite Mixed trims and writes. Blocks will be
391 trimmed first, then written to.
393 For the mixed io types, the default is to split them 50/50.
394 For certain types of io the result may still be skewed a bit,
395 since the speed may be different. It is possible to specify
396 a number of IO's to do before getting a new offset, this is
397 done by appending a ':<nr>' to the end of the string given.
398 For a random read, it would look like 'rw=randread:8' for
399 passing in an offset modifier with a value of 8. If the
400 suffix is used with a sequential IO pattern, then the value
401 specified will be added to the generated offset for each IO.
402 For instance, using rw=write:4k will skip 4k for every
403 write. It turns sequential IO into sequential IO with holes.
404 See the 'rw_sequencer' option.
406 rw_sequencer=str If an offset modifier is given by appending a number to
407 the rw=<str> line, then this option controls how that
408 number modifies the IO offset being generated. Accepted
411 sequential Generate sequential offset
412 identical Generate the same offset
414 'sequential' is only useful for random IO, where fio would
415 normally generate a new random offset for every IO. If you
416 append eg 8 to randread, you would get a new random offset for
417 every 8 IO's. The result would be a seek for only every 8
418 IO's, instead of for every IO. Use rw=randread:8 to specify
419 that. As sequential IO is already sequential, setting
420 'sequential' for that would not result in any differences.
421 'identical' behaves in a similar fashion, except it sends
422 the same offset 8 number of times before generating a new
425 kb_base=int The base unit for a kilobyte. The defacto base is 2^10, 1024.
426 Storage manufacturers like to use 10^3 or 1000 as a base
427 ten unit instead, for obvious reasons. Allow values are
428 1024 or 1000, with 1024 being the default.
430 unified_rw_reporting=bool Fio normally reports statistics on a per
431 data direction basis, meaning that read, write, and trim are
432 accounted and reported separately. If this option is set,
433 the fio will sum the results and report them as "mixed"
436 randrepeat=bool For random IO workloads, seed the generator in a predictable
437 way so that results are repeatable across repetitions.
440 randseed=int Seed the random number generators based on this seed value, to
441 be able to control what sequence of output is being generated.
442 If not set, the random sequence depends on the randrepeat
445 fallocate=str Whether pre-allocation is performed when laying down files.
448 none Do not pre-allocate space
449 posix Pre-allocate via posix_fallocate()
450 keep Pre-allocate via fallocate() with
451 FALLOC_FL_KEEP_SIZE set
452 0 Backward-compatible alias for 'none'
453 1 Backward-compatible alias for 'posix'
455 May not be available on all supported platforms. 'keep' is only
456 available on Linux.If using ZFS on Solaris this must be set to
457 'none' because ZFS doesn't support it. Default: 'posix'.
459 fadvise_hint=bool By default, fio will use fadvise() to advise the kernel
460 on what IO patterns it is likely to issue. Sometimes you
461 want to test specific IO patterns without telling the
462 kernel about it, in which case you can disable this option.
463 If set, fio will use POSIX_FADV_SEQUENTIAL for sequential
464 IO and POSIX_FADV_RANDOM for random IO.
466 fadvise_stream=int Notify the kernel what write stream ID to place these
467 writes under. Only supported on Linux. Note, this option
468 may change going forward.
470 size=int The total size of file io for this job. Fio will run until
471 this many bytes has been transferred, unless runtime is
472 limited by other options (such as 'runtime', for instance,
473 or increased/decreased by 'io_size'). Unless specific nrfiles
474 and filesize options are given, fio will divide this size
475 between the available files specified by the job. If not set,
476 fio will use the full size of the given files or devices.
477 If the files do not exist, size must be given. It is also
478 possible to give size as a percentage between 1 and 100. If
479 size=20% is given, fio will use 20% of the full size of the
480 given files or devices.
483 io_limit=int Normally fio operates within the region set by 'size', which
484 means that the 'size' option sets both the region and size of
485 IO to be performed. Sometimes that is not what you want. With
486 this option, it is possible to define just the amount of IO
487 that fio should do. For instance, if 'size' is set to 20G and
488 'io_size' is set to 5G, fio will perform IO within the first
489 20G but exit when 5G have been done. The opposite is also
490 possible - if 'size' is set to 20G, and 'io_size' is set to
491 40G, then fio will do 40G of IO within the 0..20G region.
493 filesize=int Individual file sizes. May be a range, in which case fio
494 will select sizes for files at random within the given range
495 and limited to 'size' in total (if that is given). If not
496 given, each created file is the same size.
498 file_append=bool Perform IO after the end of the file. Normally fio will
499 operate within the size of a file. If this option is set, then
500 fio will append to the file instead. This has identical
501 behavior to setting offset to the size of a file. This option
502 is ignored on non-regular files.
505 fill_fs=bool Sets size to something really large and waits for ENOSPC (no
506 space left on device) as the terminating condition. Only makes
507 sense with sequential write. For a read workload, the mount
508 point will be filled first then IO started on the result. This
509 option doesn't make sense if operating on a raw device node,
510 since the size of that is already known by the file system.
511 Additionally, writing beyond end-of-device will not return
515 bs=int The block size used for the io units. Defaults to 4k. Values
516 can be given for both read and writes. If a single int is
517 given, it will apply to both. If a second int is specified
518 after a comma, it will apply to writes only. In other words,
519 the format is either bs=read_and_write or bs=read,write,trim.
520 bs=4k,8k will thus use 4k blocks for reads, 8k blocks for
521 writes, and 8k for trims. You can terminate the list with
522 a trailing comma. bs=4k,8k, would use the default value for
523 trims.. If you only wish to set the write size, you
524 can do so by passing an empty read size - bs=,8k will set
525 8k for writes and leave the read default value.
528 ba=int At what boundary to align random IO offsets. Defaults to
529 the same as 'blocksize' the minimum blocksize given.
530 Minimum alignment is typically 512b for using direct IO,
531 though it usually depends on the hardware block size. This
532 option is mutually exclusive with using a random map for
533 files, so it will turn off that option.
535 blocksize_range=irange
536 bsrange=irange Instead of giving a single block size, specify a range
537 and fio will mix the issued io block sizes. The issued
538 io unit will always be a multiple of the minimum value
539 given (also see bs_unaligned). Applies to both reads and
540 writes, however a second range can be given after a comma.
543 bssplit=str Sometimes you want even finer grained control of the
544 block sizes issued, not just an even split between them.
545 This option allows you to weight various block sizes,
546 so that you are able to define a specific amount of
547 block sizes issued. The format for this option is:
549 bssplit=blocksize/percentage:blocksize/percentage
551 for as many block sizes as needed. So if you want to define
552 a workload that has 50% 64k blocks, 10% 4k blocks, and
553 40% 32k blocks, you would write:
555 bssplit=4k/10:64k/50:32k/40
557 Ordering does not matter. If the percentage is left blank,
558 fio will fill in the remaining values evenly. So a bssplit
559 option like this one:
561 bssplit=4k/50:1k/:32k/
563 would have 50% 4k ios, and 25% 1k and 32k ios. The percentages
564 always add up to 100, if bssplit is given a range that adds
565 up to more, it will error out.
567 bssplit also supports giving separate splits to reads and
568 writes. The format is identical to what bs= accepts. You
569 have to separate the read and write parts with a comma. So
570 if you want a workload that has 50% 2k reads and 50% 4k reads,
571 while having 90% 4k writes and 10% 8k writes, you would
574 bssplit=2k/50:4k/50,4k/90:8k/10
577 bs_unaligned If this option is given, any byte size value within bsrange
578 may be used as a block range. This typically wont work with
579 direct IO, as that normally requires sector alignment.
581 bs_is_seq_rand If this option is set, fio will use the normal read,write
582 blocksize settings as sequential,random instead. Any random
583 read or write will use the WRITE blocksize settings, and any
584 sequential read or write will use the READ blocksize setting.
586 zero_buffers If this option is given, fio will init the IO buffers to
587 all zeroes. The default is to fill them with random data.
589 refill_buffers If this option is given, fio will refill the IO buffers
590 on every submit. The default is to only fill it at init
591 time and reuse that data. Only makes sense if zero_buffers
592 isn't specified, naturally. If data verification is enabled,
593 refill_buffers is also automatically enabled.
595 scramble_buffers=bool If refill_buffers is too costly and the target is
596 using data deduplication, then setting this option will
597 slightly modify the IO buffer contents to defeat normal
598 de-dupe attempts. This is not enough to defeat more clever
599 block compression attempts, but it will stop naive dedupe of
600 blocks. Default: true.
602 buffer_compress_percentage=int If this is set, then fio will attempt to
603 provide IO buffer content (on WRITEs) that compress to
604 the specified level. Fio does this by providing a mix of
605 random data and a fixed pattern. The fixed pattern is either
606 zeroes, or the pattern specified by buffer_pattern. If the
607 pattern option is used, it might skew the compression ratio
608 slightly. Note that this is per block size unit, for file/disk
609 wide compression level that matches this setting, you'll also
610 want to set refill_buffers.
612 buffer_compress_chunk=int See buffer_compress_percentage. This
613 setting allows fio to manage how big the ranges of random
614 data and zeroed data is. Without this set, fio will
615 provide buffer_compress_percentage of blocksize random
616 data, followed by the remaining zeroed. With this set
617 to some chunk size smaller than the block size, fio can
618 alternate random and zeroed data throughout the IO
621 buffer_pattern=str If set, fio will fill the io buffers with this
622 pattern. If not set, the contents of io buffers is defined by
623 the other options related to buffer contents. The setting can
624 be any pattern of bytes, and can be prefixed with 0x for hex
625 values. It may also be a string, where the string must then
626 be wrapped with "", e.g.:
628 buffer_pattern="abcd"
632 buffer_pattern=0xdeadface
634 Also you can combine everything together in any order:
635 buffer_pattern=0xdeadface"abcd"-12
637 dedupe_percentage=int If set, fio will generate this percentage of
638 identical buffers when writing. These buffers will be
639 naturally dedupable. The contents of the buffers depend on
640 what other buffer compression settings have been set. It's
641 possible to have the individual buffers either fully
642 compressible, or not at all. This option only controls the
643 distribution of unique buffers.
645 nrfiles=int Number of files to use for this job. Defaults to 1.
647 openfiles=int Number of files to keep open at the same time. Defaults to
648 the same as nrfiles, can be set smaller to limit the number
651 file_service_type=str Defines how fio decides which file from a job to
652 service next. The following types are defined:
654 random Just choose a file at random.
656 roundrobin Round robin over open files. This
659 sequential Finish one file before moving on to
660 the next. Multiple files can still be
661 open depending on 'openfiles'.
663 The string can have a number appended, indicating how
664 often to switch to a new file. So if option random:4 is
665 given, fio will switch to a new random file after 4 ios
668 ioengine=str Defines how the job issues io to the file. The following
671 sync Basic read(2) or write(2) io. lseek(2) is
672 used to position the io location.
674 psync Basic pread(2) or pwrite(2) io.
676 vsync Basic readv(2) or writev(2) IO.
678 psyncv Basic preadv(2) or pwritev(2) IO.
680 libaio Linux native asynchronous io. Note that Linux
681 may only support queued behaviour with
682 non-buffered IO (set direct=1 or buffered=0).
683 This engine defines engine specific options.
685 posixaio glibc posix asynchronous io.
687 solarisaio Solaris native asynchronous io.
689 windowsaio Windows native asynchronous io.
691 mmap File is memory mapped and data copied
692 to/from using memcpy(3).
694 splice splice(2) is used to transfer the data and
695 vmsplice(2) to transfer data from user
698 syslet-rw Use the syslet system calls to make
699 regular read/write async.
701 sg SCSI generic sg v3 io. May either be
702 synchronous using the SG_IO ioctl, or if
703 the target is an sg character device
704 we use read(2) and write(2) for asynchronous
707 null Doesn't transfer any data, just pretends
708 to. This is mainly used to exercise fio
709 itself and for debugging/testing purposes.
711 net Transfer over the network to given host:port.
712 Depending on the protocol used, the hostname,
713 port, listen and filename options are used to
714 specify what sort of connection to make, while
715 the protocol option determines which protocol
717 This engine defines engine specific options.
719 netsplice Like net, but uses splice/vmsplice to
720 map data and send/receive.
721 This engine defines engine specific options.
723 cpuio Doesn't transfer any data, but burns CPU
724 cycles according to the cpuload= and
725 cpucycle= options. Setting cpuload=85
726 will cause that job to do nothing but burn
727 85% of the CPU. In case of SMP machines,
728 use numjobs=<no_of_cpu> to get desired CPU
729 usage, as the cpuload only loads a single
730 CPU at the desired rate.
732 guasi The GUASI IO engine is the Generic Userspace
733 Asyncronous Syscall Interface approach
736 http://www.xmailserver.org/guasi-lib.html
738 for more info on GUASI.
740 rdma The RDMA I/O engine supports both RDMA
741 memory semantics (RDMA_WRITE/RDMA_READ) and
742 channel semantics (Send/Recv) for the
743 InfiniBand, RoCE and iWARP protocols.
745 falloc IO engine that does regular fallocate to
746 simulate data transfer as fio ioengine.
747 DDIR_READ does fallocate(,mode = keep_size,)
748 DDIR_WRITE does fallocate(,mode = 0)
749 DDIR_TRIM does fallocate(,mode = punch_hole)
751 e4defrag IO engine that does regular EXT4_IOC_MOVE_EXT
752 ioctls to simulate defragment activity in
753 request to DDIR_WRITE event
755 rbd IO engine supporting direct access to Ceph
756 Rados Block Devices (RBD) via librbd without
757 the need to use the kernel rbd driver. This
758 ioengine defines engine specific options.
760 gfapi Using Glusterfs libgfapi sync interface to
761 direct access to Glusterfs volumes without
764 gfapi_async Using Glusterfs libgfapi async interface
765 to direct access to Glusterfs volumes without
766 having to go through FUSE. This ioengine
767 defines engine specific options.
769 libhdfs Read and write through Hadoop (HDFS).
770 The 'filename' option is used to specify host,
771 port of the hdfs name-node to connect. This
772 engine interprets offsets a little
773 differently. In HDFS, files once created
774 cannot be modified. So random writes are not
775 possible. To imitate this, libhdfs engine
776 expects bunch of small files to be created
777 over HDFS, and engine will randomly pick a
778 file out of those files based on the offset
779 generated by fio backend. (see the example
780 job file to create such files, use rw=write
781 option). Please note, you might want to set
782 necessary environment variables to work with
783 hdfs/libhdfs properly.
785 mtd Read, write and erase an MTD character device
786 (e.g., /dev/mtd0). Discards are treated as
787 erases. Depending on the underlying device
788 type, the I/O may have to go in a certain
789 pattern, e.g., on NAND, writing sequentially
790 to erase blocks and discarding before
791 overwriting. The writetrim mode works well
794 external Prefix to specify loading an external
795 IO engine object file. Append the engine
796 filename, eg ioengine=external:/tmp/foo.o
797 to load ioengine foo.o in /tmp.
799 iodepth=int This defines how many io units to keep in flight against
800 the file. The default is 1 for each file defined in this
801 job, can be overridden with a larger value for higher
802 concurrency. Note that increasing iodepth beyond 1 will not
803 affect synchronous ioengines (except for small degress when
804 verify_async is in use). Even async engines may impose OS
805 restrictions causing the desired depth not to be achieved.
806 This may happen on Linux when using libaio and not setting
807 direct=1, since buffered IO is not async on that OS. Keep an
808 eye on the IO depth distribution in the fio output to verify
809 that the achieved depth is as expected. Default: 1.
811 iodepth_batch_submit=int
812 iodepth_batch=int This defines how many pieces of IO to submit at once.
813 It defaults to 1 which means that we submit each IO
814 as soon as it is available, but can be raised to submit
815 bigger batches of IO at the time. If it is set to 0 the iodepth
818 iodepth_batch_complete_min=int
819 iodepth_batch_complete=int This defines how many pieces of IO to retrieve
820 at once. It defaults to 1 which means that we'll ask
821 for a minimum of 1 IO in the retrieval process from
822 the kernel. The IO retrieval will go on until we
823 hit the limit set by iodepth_low. If this variable is
824 set to 0, then fio will always check for completed
825 events before queuing more IO. This helps reduce
826 IO latency, at the cost of more retrieval system calls.
828 iodepth_batch_complete_max=int This defines maximum pieces of IO to
829 retrieve at once. This variable should be used along with
830 iodepth_batch_complete_min=int variable, specifying the range
831 of min and max amount of IO which should be retrieved. By default
832 it is equal to iodepth_batch_complete_min value.
836 iodepth_batch_complete_min=1
837 iodepth_batch_complete_max=<iodepth>
839 which means that we will retrieve at leat 1 IO and up to the
840 whole submitted queue depth. If none of IO has been completed
845 iodepth_batch_complete_min=0
846 iodepth_batch_complete_max=<iodepth>
848 which means that we can retrieve up to the whole submitted
849 queue depth, but if none of IO has been completed yet, we will
850 NOT wait and immediately exit the system call. In this example
851 we simply do polling.
853 iodepth_low=int The low water mark indicating when to start filling
854 the queue again. Defaults to the same as iodepth, meaning
855 that fio will attempt to keep the queue full at all times.
856 If iodepth is set to eg 16 and iodepth_low is set to 4, then
857 after fio has filled the queue of 16 requests, it will let
858 the depth drain down to 4 before starting to fill it again.
860 io_submit_mode=str This option controls how fio submits the IO to
861 the IO engine. The default is 'inline', which means that the
862 fio job threads submit and reap IO directly. If set to
863 'offload', the job threads will offload IO submission to a
864 dedicated pool of IO threads. This requires some coordination
865 and thus has a bit of extra overhead, especially for lower
866 queue depth IO where it can increase latencies. The benefit
867 is that fio can manage submission rates independently of
868 the device completion rates. This avoids skewed latency
869 reporting if IO gets back up on the device side (the
870 coordinated omission problem).
872 direct=bool If value is true, use non-buffered io. This is usually
873 O_DIRECT. Note that ZFS on Solaris doesn't support direct io.
874 On Windows the synchronous ioengines don't support direct io.
876 atomic=bool If value is true, attempt to use atomic direct IO. Atomic
877 writes are guaranteed to be stable once acknowledged by
878 the operating system. Only Linux supports O_ATOMIC right
881 buffered=bool If value is true, use buffered io. This is the opposite
882 of the 'direct' option. Defaults to true.
884 offset=int Start io at the given offset in the file. The data before
885 the given offset will not be touched. This effectively
886 caps the file size at real_size - offset.
888 offset_increment=int If this is provided, then the real offset becomes
889 offset + offset_increment * thread_number, where the thread
890 number is a counter that starts at 0 and is incremented for
891 each sub-job (i.e. when numjobs option is specified). This
892 option is useful if there are several jobs which are intended
893 to operate on a file in parallel disjoint segments, with
894 even spacing between the starting points.
896 number_ios=int Fio will normally perform IOs until it has exhausted the size
897 of the region set by size=, or if it exhaust the allocated
898 time (or hits an error condition). With this setting, the
899 range/size can be set independently of the number of IOs to
900 perform. When fio reaches this number, it will exit normally
901 and report status. Note that this does not extend the amount
902 of IO that will be done, it will only stop fio if this
903 condition is met before other end-of-job criteria.
905 fsync=int If writing to a file, issue a sync of the dirty data
906 for every number of blocks given. For example, if you give
907 32 as a parameter, fio will sync the file for every 32
908 writes issued. If fio is using non-buffered io, we may
909 not sync the file. The exception is the sg io engine, which
910 synchronizes the disk cache anyway.
912 fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
914 In FreeBSD and Windows there is no fdatasync(), this falls back
917 sync_file_range=str:val Use sync_file_range() for every 'val' number of
918 write operations. Fio will track range of writes that
919 have happened since the last sync_file_range() call. 'str'
920 can currently be one or more of:
922 wait_before SYNC_FILE_RANGE_WAIT_BEFORE
923 write SYNC_FILE_RANGE_WRITE
924 wait_after SYNC_FILE_RANGE_WAIT_AFTER
926 So if you do sync_file_range=wait_before,write:8, fio would
927 use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
928 every 8 writes. Also see the sync_file_range(2) man page.
929 This option is Linux specific.
931 overwrite=bool If true, writes to a file will always overwrite existing
932 data. If the file doesn't already exist, it will be
933 created before the write phase begins. If the file exists
934 and is large enough for the specified write phase, nothing
937 end_fsync=bool If true, fsync file contents when a write stage has completed.
939 fsync_on_close=bool If true, fio will fsync() a dirty file on close.
940 This differs from end_fsync in that it will happen on every
941 file close, not just at the end of the job.
943 rwmixread=int How large a percentage of the mix should be reads.
945 rwmixwrite=int How large a percentage of the mix should be writes. If both
946 rwmixread and rwmixwrite is given and the values do not add
947 up to 100%, the latter of the two will be used to override
948 the first. This may interfere with a given rate setting,
949 if fio is asked to limit reads or writes to a certain rate.
950 If that is the case, then the distribution may be skewed.
952 random_distribution=str:float By default, fio will use a completely uniform
953 random distribution when asked to perform random IO. Sometimes
954 it is useful to skew the distribution in specific ways,
955 ensuring that some parts of the data is more hot than others.
956 fio includes the following distribution models:
958 random Uniform random distribution
959 zipf Zipf distribution
960 pareto Pareto distribution
962 When using a zipf or pareto distribution, an input value
963 is also needed to define the access pattern. For zipf, this
964 is the zipf theta. For pareto, it's the pareto power. Fio
965 includes a test program, genzipf, that can be used visualize
966 what the given input values will yield in terms of hit rates.
967 If you wanted to use zipf with a theta of 1.2, you would use
968 random_distribution=zipf:1.2 as the option. If a non-uniform
969 model is used, fio will disable use of the random map.
971 percentage_random=int For a random workload, set how big a percentage should
972 be random. This defaults to 100%, in which case the workload
973 is fully random. It can be set from anywhere from 0 to 100.
974 Setting it to 0 would make the workload fully sequential. Any
975 setting in between will result in a random mix of sequential
976 and random IO, at the given percentages. It is possible to
977 set different values for reads, writes, and trim. To do so,
978 simply use a comma separated list. See blocksize.
980 norandommap Normally fio will cover every block of the file when doing
981 random IO. If this option is given, fio will just get a
982 new random offset without looking at past io history. This
983 means that some blocks may not be read or written, and that
984 some blocks may be read/written more than once. If this option
985 is used with verify= and multiple blocksizes (via bsrange=),
986 only intact blocks are verified, i.e., partially-overwritten
989 softrandommap=bool See norandommap. If fio runs with the random block map
990 enabled and it fails to allocate the map, if this option is
991 set it will continue without a random block map. As coverage
992 will not be as complete as with random maps, this option is
995 random_generator=str Fio supports the following engines for generating
996 IO offsets for random IO:
998 tausworthe Strong 2^88 cycle random number generator
999 lfsr Linear feedback shift register generator
1000 tausworthe64 Strong 64-bit 2^258 cycle random number
1003 Tausworthe is a strong random number generator, but it
1004 requires tracking on the side if we want to ensure that
1005 blocks are only read or written once. LFSR guarantees
1006 that we never generate the same offset twice, and it's
1007 also less computationally expensive. It's not a true
1008 random generator, however, though for IO purposes it's
1009 typically good enough. LFSR only works with single
1010 block sizes, not with workloads that use multiple block
1011 sizes. If used with such a workload, fio may read or write
1012 some blocks multiple times.
1014 nice=int Run the job with the given nice value. See man nice(2).
1016 prio=int Set the io priority value of this job. Linux limits us to
1017 a positive value between 0 and 7, with 0 being the highest.
1020 prioclass=int Set the io priority class. See man ionice(1).
1022 thinktime=int Stall the job x microseconds after an io has completed before
1023 issuing the next. May be used to simulate processing being
1024 done by an application. See thinktime_blocks and
1028 Only valid if thinktime is set - pretend to spend CPU time
1029 doing something with the data received, before falling back
1030 to sleeping for the rest of the period specified by
1033 thinktime_blocks=int
1034 Only valid if thinktime is set - control how many blocks
1035 to issue, before waiting 'thinktime' usecs. If not set,
1036 defaults to 1 which will make fio wait 'thinktime' usecs
1037 after every block. This effectively makes any queue depth
1038 setting redundant, since no more than 1 IO will be queued
1039 before we have to complete it and do our thinktime. In
1040 other words, this setting effectively caps the queue depth
1041 if the latter is larger.
1043 rate=int Cap the bandwidth used by this job. The number is in bytes/sec,
1044 the normal suffix rules apply. You can use rate=500k to limit
1045 reads and writes to 500k each, or you can specify read and
1046 writes separately. Using rate=1m,500k would limit reads to
1047 1MB/sec and writes to 500KB/sec. Capping only reads or
1048 writes can be done with rate=,500k or rate=500k,. The former
1049 will only limit writes (to 500KB/sec), the latter will only
1052 rate_min=int Tell fio to do whatever it can to maintain at least this
1053 bandwidth. Failing to meet this requirement, will cause
1054 the job to exit. The same format as rate is used for
1055 read vs write separation.
1057 rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
1058 as rate, just specified independently of bandwidth. If the
1059 job is given a block size range instead of a fixed value,
1060 the smallest block size is used as the metric. The same format
1061 as rate is used for read vs write separation.
1063 rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
1064 the job to exit. The same format as rate is used for read vs
1067 rate_process=str This option controls how fio manages rated IO
1068 submissions. The default is 'linear', which submits IO in a
1069 linear fashion with fixed delays between IOs that gets
1070 adjusted based on IO completion rates. If this is set to
1071 'poisson', fio will submit IO based on a more real world
1072 random request flow, known as the Poisson process
1073 (https://en.wikipedia.org/wiki/Poisson_process).
1075 latency_target=int If set, fio will attempt to find the max performance
1076 point that the given workload will run at while maintaining a
1077 latency below this target. The values is given in microseconds.
1078 See latency_window and latency_percentile
1080 latency_window=int Used with latency_target to specify the sample window
1081 that the job is run at varying queue depths to test the
1082 performance. The value is given in microseconds.
1084 latency_percentile=float The percentage of IOs that must fall within the
1085 criteria specified by latency_target and latency_window. If not
1086 set, this defaults to 100.0, meaning that all IOs must be equal
1087 or below to the value set by latency_target.
1089 max_latency=int If set, fio will exit the job if it exceeds this maximum
1090 latency. It will exit with an ETIME error.
1092 rate_cycle=int Average bandwidth for 'rate' and 'rate_min' over this number
1095 cpumask=int Set the CPU affinity of this job. The parameter given is a
1096 bitmask of allowed CPU's the job may run on. So if you want
1097 the allowed CPUs to be 1 and 5, you would pass the decimal
1098 value of (1 << 1 | 1 << 5), or 34. See man
1099 sched_setaffinity(2). This may not work on all supported
1100 operating systems or kernel versions. This option doesn't
1101 work well for a higher CPU count than what you can store in
1102 an integer mask, so it can only control cpus 1-32. For
1103 boxes with larger CPU counts, use cpus_allowed.
1105 cpus_allowed=str Controls the same options as cpumask, but it allows a text
1106 setting of the permitted CPUs instead. So to use CPUs 1 and
1107 5, you would specify cpus_allowed=1,5. This options also
1108 allows a range of CPUs. Say you wanted a binding to CPUs
1109 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15.
1111 cpus_allowed_policy=str Set the policy of how fio distributes the CPUs
1112 specified by cpus_allowed or cpumask. Two policies are
1115 shared All jobs will share the CPU set specified.
1116 split Each job will get a unique CPU from the CPU set.
1118 'shared' is the default behaviour, if the option isn't
1119 specified. If split is specified, then fio will will assign
1120 one cpu per job. If not enough CPUs are given for the jobs
1121 listed, then fio will roundrobin the CPUs in the set.
1123 numa_cpu_nodes=str Set this job running on spcified NUMA nodes' CPUs. The
1124 arguments allow comma delimited list of cpu numbers,
1125 A-B ranges, or 'all'. Note, to enable numa options support,
1126 fio must be built on a system with libnuma-dev(el) installed.
1128 numa_mem_policy=str Set this job's memory policy and corresponding NUMA
1129 nodes. Format of the argements:
1131 `mode' is one of the following memory policy:
1132 default, prefer, bind, interleave, local
1133 For `default' and `local' memory policy, no node is
1134 needed to be specified.
1135 For `prefer', only one node is allowed.
1136 For `bind' and `interleave', it allow comma delimited
1137 list of numbers, A-B ranges, or 'all'.
1139 startdelay=time Start this job the specified number of seconds after fio
1140 has started. Only useful if the job file contains several
1141 jobs, and you want to delay starting some jobs to a certain
1144 runtime=time Tell fio to terminate processing after the specified number
1145 of seconds. It can be quite hard to determine for how long
1146 a specified job will run, so this parameter is handy to
1147 cap the total runtime to a given time.
1149 time_based If set, fio will run for the duration of the runtime
1150 specified even if the file(s) are completely read or
1151 written. It will simply loop over the same workload
1152 as many times as the runtime allows.
1154 ramp_time=time If set, fio will run the specified workload for this amount
1155 of time before logging any performance numbers. Useful for
1156 letting performance settle before logging results, thus
1157 minimizing the runtime required for stable results. Note
1158 that the ramp_time is considered lead in time for a job,
1159 thus it will increase the total runtime if a special timeout
1160 or runtime is specified.
1162 invalidate=bool Invalidate the buffer/page cache parts for this file prior
1163 to starting io. Defaults to true.
1165 sync=bool Use sync io for buffered writes. For the majority of the
1166 io engines, this means using O_SYNC.
1169 mem=str Fio can use various types of memory as the io unit buffer.
1170 The allowed values are:
1172 malloc Use memory from malloc(3) as the buffers.
1174 shm Use shared memory as the buffers. Allocated
1177 shmhuge Same as shm, but use huge pages as backing.
1179 mmap Use mmap to allocate buffers. May either be
1180 anonymous memory, or can be file backed if
1181 a filename is given after the option. The
1182 format is mem=mmap:/path/to/file.
1184 mmaphuge Use a memory mapped huge file as the buffer
1185 backing. Append filename after mmaphuge, ala
1186 mem=mmaphuge:/hugetlbfs/file
1188 mmapshared Same as mmap, but use a MMAP_SHARED
1191 The area allocated is a function of the maximum allowed
1192 bs size for the job, multiplied by the io depth given. Note
1193 that for shmhuge and mmaphuge to work, the system must have
1194 free huge pages allocated. This can normally be checked
1195 and set by reading/writing /proc/sys/vm/nr_hugepages on a
1196 Linux system. Fio assumes a huge page is 4MB in size. So
1197 to calculate the number of huge pages you need for a given
1198 job file, add up the io depth of all jobs (normally one unless
1199 iodepth= is used) and multiply by the maximum bs set. Then
1200 divide that number by the huge page size. You can see the
1201 size of the huge pages in /proc/meminfo. If no huge pages
1202 are allocated by having a non-zero number in nr_hugepages,
1203 using mmaphuge or shmhuge will fail. Also see hugepage-size.
1205 mmaphuge also needs to have hugetlbfs mounted and the file
1206 location should point there. So if it's mounted in /huge,
1207 you would use mem=mmaphuge:/huge/somefile.
1209 iomem_align=int This indiciates the memory alignment of the IO memory buffers.
1210 Note that the given alignment is applied to the first IO unit
1211 buffer, if using iodepth the alignment of the following buffers
1212 are given by the bs used. In other words, if using a bs that is
1213 a multiple of the page sized in the system, all buffers will
1214 be aligned to this value. If using a bs that is not page
1215 aligned, the alignment of subsequent IO memory buffers is the
1216 sum of the iomem_align and bs used.
1219 Defines the size of a huge page. Must at least be equal
1220 to the system setting, see /proc/meminfo. Defaults to 4MB.
1221 Should probably always be a multiple of megabytes, so using
1222 hugepage-size=Xm is the preferred way to set this to avoid
1223 setting a non-pow-2 bad value.
1225 exitall When one job finishes, terminate the rest. The default is
1226 to wait for each job to finish, sometimes that is not the
1229 bwavgtime=int Average the calculated bandwidth over the given time. Value
1230 is specified in milliseconds.
1232 iopsavgtime=int Average the calculated IOPS over the given time. Value
1233 is specified in milliseconds.
1235 create_serialize=bool If true, serialize the file creating for the jobs.
1236 This may be handy to avoid interleaving of data
1237 files, which may greatly depend on the filesystem
1238 used and even the number of processors in the system.
1240 create_fsync=bool fsync the data file after creation. This is the
1243 create_on_open=bool Don't pre-setup the files for IO, just create open()
1244 when it's time to do IO to that file.
1246 create_only=bool If true, fio will only run the setup phase of the job.
1247 If files need to be laid out or updated on disk, only
1248 that will be done. The actual job contents are not
1251 allow_file_create=bool If true, fio is permitted to create files as part
1252 of its workload. This is the default behavior. If this
1253 option is false, then fio will error out if the files it
1254 needs to use don't already exist. Default: true.
1256 allow_mounted_write=bool If this isn't set, fio will abort jobs that
1257 are destructive (eg that write) to what appears to be a
1258 mounted device or partition. This should help catch creating
1259 inadvertently destructive tests, not realizing that the test
1260 will destroy data on the mounted file system. Default: false.
1262 pre_read=bool If this is given, files will be pre-read into memory before
1263 starting the given IO operation. This will also clear
1264 the 'invalidate' flag, since it is pointless to pre-read
1265 and then drop the cache. This will only work for IO engines
1266 that are seekable, since they allow you to read the same data
1267 multiple times. Thus it will not work on eg network or splice
1270 unlink=bool Unlink the job files when done. Not the default, as repeated
1271 runs of that job would then waste time recreating the file
1272 set again and again.
1274 loops=int Run the specified number of iterations of this job. Used
1275 to repeat the same workload a given number of times. Defaults
1278 verify_only Do not perform specified workload---only verify data still
1279 matches previous invocation of this workload. This option
1280 allows one to check data multiple times at a later date
1281 without overwriting it. This option makes sense only for
1282 workloads that write data, and does not support workloads
1283 with the time_based option set.
1285 do_verify=bool Run the verify phase after a write phase. Only makes sense if
1286 verify is set. Defaults to 1.
1288 verify=str If writing to a file, fio can verify the file contents
1289 after each iteration of the job. Each verification method also implies
1290 verification of special header, which is written to the beginning of
1291 each block. This header also includes meta information, like offset
1292 of the block, block number, timestamp when block was written, etc.
1293 verify=str can be combined with verify_pattern=str option.
1294 The allowed values are:
1296 md5 Use an md5 sum of the data area and store
1297 it in the header of each block.
1299 crc64 Use an experimental crc64 sum of the data
1300 area and store it in the header of each
1303 crc32c Use a crc32c sum of the data area and store
1304 it in the header of each block.
1306 crc32c-intel Use hardware assisted crc32c calcuation
1307 provided on SSE4.2 enabled processors. Falls
1308 back to regular software crc32c, if not
1309 supported by the system.
1311 crc32 Use a crc32 sum of the data area and store
1312 it in the header of each block.
1314 crc16 Use a crc16 sum of the data area and store
1315 it in the header of each block.
1317 crc7 Use a crc7 sum of the data area and store
1318 it in the header of each block.
1320 xxhash Use xxhash as the checksum function. Generally
1321 the fastest software checksum that fio
1324 sha512 Use sha512 as the checksum function.
1326 sha256 Use sha256 as the checksum function.
1328 sha1 Use optimized sha1 as the checksum function.
1330 meta This option is deprecated, since now meta information is
1331 included in generic verification header and meta verification
1332 happens by default. For detailed information see the description
1333 of the verify=str setting. This option is kept because of
1334 compatibility's sake with old configurations. Do not use it.
1336 pattern Verify a strict pattern. Normally fio includes
1337 a header with some basic information and
1338 checksumming, but if this option is set, only
1339 the specific pattern set with 'verify_pattern'
1342 null Only pretend to verify. Useful for testing
1343 internals with ioengine=null, not for much
1346 This option can be used for repeated burn-in tests of a
1347 system to make sure that the written data is also
1348 correctly read back. If the data direction given is
1349 a read or random read, fio will assume that it should
1350 verify a previously written file. If the data direction
1351 includes any form of write, the verify will be of the
1354 verifysort=bool If set, fio will sort written verify blocks when it deems
1355 it faster to read them back in a sorted manner. This is
1356 often the case when overwriting an existing file, since
1357 the blocks are already laid out in the file system. You
1358 can ignore this option unless doing huge amounts of really
1359 fast IO where the red-black tree sorting CPU time becomes
1362 verify_offset=int Swap the verification header with data somewhere else
1363 in the block before writing. Its swapped back before
1366 verify_interval=int Write the verification header at a finer granularity
1367 than the blocksize. It will be written for chunks the
1368 size of header_interval. blocksize should divide this
1371 verify_pattern=str If set, fio will fill the io buffers with this
1372 pattern. Fio defaults to filling with totally random
1373 bytes, but sometimes it's interesting to fill with a known
1374 pattern for io verification purposes. Depending on the
1375 width of the pattern, fio will fill 1/2/3/4 bytes of the
1376 buffer at the time(it can be either a decimal or a hex number).
1377 The verify_pattern if larger than a 32-bit quantity has to
1378 be a hex number that starts with either "0x" or "0X". Use
1379 with verify=str. Also, verify_pattern supports %o format,
1380 which means that for each block offset will be written and
1381 then verifyied back, e.g.:
1385 Or use combination of everything:
1386 verify_pattern=0xff%o"abcd"-12
1388 verify_fatal=bool Normally fio will keep checking the entire contents
1389 before quitting on a block verification failure. If this
1390 option is set, fio will exit the job on the first observed
1393 verify_dump=bool If set, dump the contents of both the original data
1394 block and the data block we read off disk to files. This
1395 allows later analysis to inspect just what kind of data
1396 corruption occurred. Off by default.
1398 verify_async=int Fio will normally verify IO inline from the submitting
1399 thread. This option takes an integer describing how many
1400 async offload threads to create for IO verification instead,
1401 causing fio to offload the duty of verifying IO contents
1402 to one or more separate threads. If using this offload
1403 option, even sync IO engines can benefit from using an
1404 iodepth setting higher than 1, as it allows them to have
1405 IO in flight while verifies are running.
1407 verify_async_cpus=str Tell fio to set the given CPU affinity on the
1408 async IO verification threads. See cpus_allowed for the
1411 verify_backlog=int Fio will normally verify the written contents of a
1412 job that utilizes verify once that job has completed. In
1413 other words, everything is written then everything is read
1414 back and verified. You may want to verify continually
1415 instead for a variety of reasons. Fio stores the meta data
1416 associated with an IO block in memory, so for large
1417 verify workloads, quite a bit of memory would be used up
1418 holding this meta data. If this option is enabled, fio
1419 will write only N blocks before verifying these blocks.
1421 verify_backlog_batch=int Control how many blocks fio will verify
1422 if verify_backlog is set. If not set, will default to
1423 the value of verify_backlog (meaning the entire queue
1424 is read back and verified). If verify_backlog_batch is
1425 less than verify_backlog then not all blocks will be verified,
1426 if verify_backlog_batch is larger than verify_backlog, some
1427 blocks will be verified more than once.
1429 verify_state_save=bool When a job exits during the write phase of a verify
1430 workload, save its current state. This allows fio to replay
1431 up until that point, if the verify state is loaded for the
1432 verify read phase. The format of the filename is, roughly,
1433 <type>-<jobname>-<jobindex>-verify.state. <type> is "local"
1434 for a local run, "sock" for a client/server socket connection,
1435 and "ip" (192.168.0.1, for instance) for a networked
1436 client/server connection.
1438 verify_state_load=bool If a verify termination trigger was used, fio stores
1439 the current write state of each thread. This can be used at
1440 verification time so that fio knows how far it should verify.
1441 Without this information, fio will run a full verification
1442 pass, according to the settings in the job file used.
1445 wait_for_previous Wait for preceding jobs in the job file to exit, before
1446 starting this one. Can be used to insert serialization
1447 points in the job file. A stone wall also implies starting
1448 a new reporting group.
1450 new_group Start a new reporting group. See: group_reporting.
1452 numjobs=int Create the specified number of clones of this job. May be
1453 used to setup a larger number of threads/processes doing
1454 the same thing. Each thread is reported separately; to see
1455 statistics for all clones as a whole, use group_reporting in
1456 conjunction with new_group.
1458 group_reporting It may sometimes be interesting to display statistics for
1459 groups of jobs as a whole instead of for each individual job.
1460 This is especially true if 'numjobs' is used; looking at
1461 individual thread/process output quickly becomes unwieldy.
1462 To see the final report per-group instead of per-job, use
1463 'group_reporting'. Jobs in a file will be part of the same
1464 reporting group, unless if separated by a stonewall, or by
1467 thread fio defaults to forking jobs, however if this option is
1468 given, fio will use pthread_create(3) to create threads
1471 zonesize=int Divide a file into zones of the specified size. See zoneskip.
1473 zoneskip=int Skip the specified number of bytes when zonesize data has
1474 been read. The two zone options can be used to only do
1475 io on zones of a file.
1477 write_iolog=str Write the issued io patterns to the specified file. See
1478 read_iolog. Specify a separate file for each job, otherwise
1479 the iologs will be interspersed and the file may be corrupt.
1481 read_iolog=str Open an iolog with the specified file name and replay the
1482 io patterns it contains. This can be used to store a
1483 workload and replay it sometime later. The iolog given
1484 may also be a blktrace binary file, which allows fio
1485 to replay a workload captured by blktrace. See blktrace
1486 for how to capture such logging data. For blktrace replay,
1487 the file needs to be turned into a blkparse binary data
1488 file first (blkparse <device> -o /dev/null -d file_for_fio.bin).
1490 replay_no_stall=int When replaying I/O with read_iolog the default behavior
1491 is to attempt to respect the time stamps within the log and
1492 replay them with the appropriate delay between IOPS. By
1493 setting this variable fio will not respect the timestamps and
1494 attempt to replay them as fast as possible while still
1495 respecting ordering. The result is the same I/O pattern to a
1496 given device, but different timings.
1498 replay_redirect=str While replaying I/O patterns using read_iolog the
1499 default behavior is to replay the IOPS onto the major/minor
1500 device that each IOP was recorded from. This is sometimes
1501 undesirable because on a different machine those major/minor
1502 numbers can map to a different device. Changing hardware on
1503 the same system can also result in a different major/minor
1504 mapping. Replay_redirect causes all IOPS to be replayed onto
1505 the single specified device regardless of the device it was
1506 recorded from. i.e. replay_redirect=/dev/sdc would cause all
1507 IO in the blktrace to be replayed onto /dev/sdc. This means
1508 multiple devices will be replayed onto a single, if the trace
1509 contains multiple devices. If you want multiple devices to be
1510 replayed concurrently to multiple redirected devices you must
1511 blkparse your trace into separate traces and replay them with
1512 independent fio invocations. Unfortuantely this also breaks
1513 the strict time ordering between multiple device accesses.
1515 replay_align=int Force alignment of IO offsets and lengths in a trace
1516 to this power of 2 value.
1518 replay_scale=int Scale sector offsets down by this factor when
1521 per_job_logs=bool If set, this generates bw/clat/iops log with per
1522 file private filenames. If not set, jobs with identical names
1523 will share the log filename. Default: true.
1525 write_bw_log=str If given, write a bandwidth log of the jobs in this job
1526 file. Can be used to store data of the bandwidth of the
1527 jobs in their lifetime. The included fio_generate_plots
1528 script uses gnuplot to turn these text files into nice
1529 graphs. See write_lat_log for behaviour of given
1530 filename. For this option, the suffix is _bw.x.log, where
1531 x is the index of the job (1..N, where N is the number of
1532 jobs). If 'per_job_logs' is false, then the filename will not
1533 include the job index.
1535 write_lat_log=str Same as write_bw_log, except that this option stores io
1536 submission, completion, and total latencies instead. If no
1537 filename is given with this option, the default filename of
1538 "jobname_type.log" is used. Even if the filename is given,
1539 fio will still append the type of log. So if one specifies
1543 The actual log names will be foo_slat.x.log, foo_clat.x.log,
1544 and foo_lat.x.log, where x is the index of the job (1..N,
1545 where N is the number of jobs). This helps fio_generate_plot
1546 fine the logs automatically. If 'per_job_logs' is false, then
1547 the filename will not include the job index.
1550 write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is
1551 given with this option, the default filename of
1552 "jobname_type.x.log" is used,where x is the index of the job
1553 (1..N, where N is the number of jobs). Even if the filename
1554 is given, fio will still append the type of log. If
1555 'per_job_logs' is false, then the filename will not include
1558 log_avg_msec=int By default, fio will log an entry in the iops, latency,
1559 or bw log for every IO that completes. When writing to the
1560 disk log, that can quickly grow to a very large size. Setting
1561 this option makes fio average the each log entry over the
1562 specified period of time, reducing the resolution of the log.
1565 log_offset=int If this is set, the iolog options will include the byte
1566 offset for the IO entry as well as the other data values.
1568 log_compression=int If this is set, fio will compress the IO logs as
1569 it goes, to keep the memory footprint lower. When a log
1570 reaches the specified size, that chunk is removed and
1571 compressed in the background. Given that IO logs are
1572 fairly highly compressible, this yields a nice memory
1573 savings for longer runs. The downside is that the
1574 compression will consume some background CPU cycles, so
1575 it may impact the run. This, however, is also true if
1576 the logging ends up consuming most of the system memory.
1577 So pick your poison. The IO logs are saved normally at the
1578 end of a run, by decompressing the chunks and storing them
1579 in the specified log file. This feature depends on the
1580 availability of zlib.
1582 log_store_compressed=bool If set, and log_compression is also set,
1583 fio will store the log files in a compressed format. They
1584 can be decompressed with fio, using the --inflate-log
1585 command line parameter. The files will be stored with a
1588 block_error_percentiles=bool If set, record errors in trim block-sized
1589 units from writes and trims and output a histogram of
1590 how many trims it took to get to errors, and what kind
1591 of error was encountered.
1593 lockmem=int Pin down the specified amount of memory with mlock(2). Can
1594 potentially be used instead of removing memory or booting
1595 with less memory to simulate a smaller amount of memory.
1596 The amount specified is per worker.
1598 exec_prerun=str Before running this job, issue the command specified
1599 through system(3). Output is redirected in a file called
1602 exec_postrun=str After the job completes, issue the command specified
1603 though system(3). Output is redirected in a file called
1604 jobname.postrun.txt.
1606 ioscheduler=str Attempt to switch the device hosting the file to the specified
1607 io scheduler before running.
1609 disk_util=bool Generate disk utilization statistics, if the platform
1610 supports it. Defaults to on.
1612 disable_lat=bool Disable measurements of total latency numbers. Useful
1613 only for cutting back the number of calls to gettimeofday,
1614 as that does impact performance at really high IOPS rates.
1615 Note that to really get rid of a large amount of these
1616 calls, this option must be used with disable_slat and
1619 disable_clat=bool Disable measurements of completion latency numbers. See
1622 disable_slat=bool Disable measurements of submission latency numbers. See
1625 disable_bw=bool Disable measurements of throughput/bandwidth numbers. See
1628 clat_percentiles=bool Enable the reporting of percentiles of
1629 completion latencies.
1631 percentile_list=float_list Overwrite the default list of percentiles
1632 for completion latencies and the block error histogram.
1633 Each number is a floating number in the range (0,100],
1634 and the maximum length of the list is 20. Use ':'
1635 to separate the numbers, and list the numbers in ascending
1636 order. For example, --percentile_list=99.5:99.9 will cause
1637 fio to report the values of completion latency below which
1638 99.5% and 99.9% of the observed latencies fell, respectively.
1640 clocksource=str Use the given clocksource as the base of timing. The
1641 supported options are:
1643 gettimeofday gettimeofday(2)
1645 clock_gettime clock_gettime(2)
1647 cpu Internal CPU clock source
1649 cpu is the preferred clocksource if it is reliable, as it
1650 is very fast (and fio is heavy on time calls). Fio will
1651 automatically use this clocksource if it's supported and
1652 considered reliable on the system it is running on, unless
1653 another clocksource is specifically set. For x86/x86-64 CPUs,
1654 this means supporting TSC Invariant.
1656 gtod_reduce=bool Enable all of the gettimeofday() reducing options
1657 (disable_clat, disable_slat, disable_bw) plus reduce
1658 precision of the timeout somewhat to really shrink
1659 the gettimeofday() call count. With this option enabled,
1660 we only do about 0.4% of the gtod() calls we would have
1661 done if all time keeping was enabled.
1663 gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of
1664 execution to just getting the current time. Fio (and
1665 databases, for instance) are very intensive on gettimeofday()
1666 calls. With this option, you can set one CPU aside for
1667 doing nothing but logging current time to a shared memory
1668 location. Then the other threads/processes that run IO
1669 workloads need only copy that segment, instead of entering
1670 the kernel with a gettimeofday() call. The CPU set aside
1671 for doing these time calls will be excluded from other
1672 uses. Fio will manually clear it from the CPU mask of other
1675 continue_on_error=str Normally fio will exit the job on the first observed
1676 failure. If this option is set, fio will continue the job when
1677 there is a 'non-fatal error' (EIO or EILSEQ) until the runtime
1678 is exceeded or the I/O size specified is completed. If this
1679 option is used, there are two more stats that are appended,
1680 the total error count and the first error. The error field
1681 given in the stats is the first error that was hit during the
1684 The allowed values are:
1686 none Exit on any IO or verify errors.
1688 read Continue on read errors, exit on all others.
1690 write Continue on write errors, exit on all others.
1692 io Continue on any IO error, exit on all others.
1694 verify Continue on verify errors, exit on all others.
1696 all Continue on all errors.
1698 0 Backward-compatible alias for 'none'.
1700 1 Backward-compatible alias for 'all'.
1702 ignore_error=str Sometimes you want to ignore some errors during test
1703 in that case you can specify error list for each error type.
1704 ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST
1705 errors for given error type is separated with ':'. Error
1706 may be symbol ('ENOSPC', 'ENOMEM') or integer.
1708 ignore_error=EAGAIN,ENOSPC:122
1709 This option will ignore EAGAIN from READ, and ENOSPC and
1710 122(EDQUOT) from WRITE.
1712 error_dump=bool If set dump every error even if it is non fatal, true
1713 by default. If disabled only fatal error will be dumped
1715 cgroup=str Add job to this control group. If it doesn't exist, it will
1716 be created. The system must have a mounted cgroup blkio
1717 mount point for this to work. If your system doesn't have it
1718 mounted, you can do so with:
1720 # mount -t cgroup -o blkio none /cgroup
1722 cgroup_weight=int Set the weight of the cgroup to this value. See
1723 the documentation that comes with the kernel, allowed values
1724 are in the range of 100..1000.
1726 cgroup_nodelete=bool Normally fio will delete the cgroups it has created after
1727 the job completion. To override this behavior and to leave
1728 cgroups around after the job completion, set cgroup_nodelete=1.
1729 This can be useful if one wants to inspect various cgroup
1730 files after job completion. Default: false
1732 uid=int Instead of running as the invoking user, set the user ID to
1733 this value before the thread/process does any work.
1735 gid=int Set group ID, see uid.
1737 flow_id=int The ID of the flow. If not specified, it defaults to being a
1738 global flow. See flow.
1740 flow=int Weight in token-based flow control. If this value is used, then
1741 there is a 'flow counter' which is used to regulate the
1742 proportion of activity between two or more jobs. fio attempts
1743 to keep this flow counter near zero. The 'flow' parameter
1744 stands for how much should be added or subtracted to the flow
1745 counter on each iteration of the main I/O loop. That is, if
1746 one job has flow=8 and another job has flow=-1, then there
1747 will be a roughly 1:8 ratio in how much one runs vs the other.
1749 flow_watermark=int The maximum value that the absolute value of the flow
1750 counter is allowed to reach before the job must wait for a
1751 lower value of the counter.
1753 flow_sleep=int The period of time, in microseconds, to wait after the flow
1754 watermark has been exceeded before retrying operations
1756 In addition, there are some parameters which are only valid when a specific
1757 ioengine is in use. These are used identically to normal parameters, with the
1758 caveat that when used on the command line, they must come after the ioengine
1759 that defines them is selected.
1761 [libaio] userspace_reap Normally, with the libaio engine in use, fio will use
1762 the io_getevents system call to reap newly returned events.
1763 With this flag turned on, the AIO ring will be read directly
1764 from user-space to reap events. The reaping mode is only
1765 enabled when polling for a minimum of 0 events (eg when
1766 iodepth_batch_complete=0).
1768 [cpu] cpuload=int Attempt to use the specified percentage of CPU cycles.
1770 [cpu] cpuchunks=int Split the load into cycles of the given time. In
1773 [cpu] exit_on_io_done=bool Detect when IO threads are done, then exit.
1775 [netsplice] hostname=str
1776 [net] hostname=str The host name or IP address to use for TCP or UDP based IO.
1777 If the job is a TCP listener or UDP reader, the hostname is not
1778 used and must be omitted unless it is a valid UDP multicast
1781 [netsplice] port=int
1782 [net] port=int The TCP or UDP port to bind to or connect to. If this is used
1783 with numjobs to spawn multiple instances of the same job type, then this will
1784 be the starting port number since fio will use a range of ports.
1786 [netsplice] interface=str
1787 [net] interface=str The IP address of the network interface used to send or
1788 receive UDP multicast
1791 [net] ttl=int Time-to-live value for outgoing UDP multicast packets.
1794 [netsplice] nodelay=bool
1795 [net] nodelay=bool Set TCP_NODELAY on TCP connections.
1797 [netsplice] protocol=str
1798 [netsplice] proto=str
1800 [net] proto=str The network protocol to use. Accepted values are:
1802 tcp Transmission control protocol
1803 tcpv6 Transmission control protocol V6
1804 udp User datagram protocol
1805 udpv6 User datagram protocol V6
1806 unix UNIX domain socket
1808 When the protocol is TCP or UDP, the port must also be given,
1809 as well as the hostname if the job is a TCP listener or UDP
1810 reader. For unix sockets, the normal filename option should be
1811 used and the port is invalid.
1813 [net] listen For TCP network connections, tell fio to listen for incoming
1814 connections rather than initiating an outgoing connection. The
1815 hostname must be omitted if this option is used.
1817 [net] pingpong Normaly a network writer will just continue writing data, and
1818 a network reader will just consume packages. If pingpong=1
1819 is set, a writer will send its normal payload to the reader,
1820 then wait for the reader to send the same payload back. This
1821 allows fio to measure network latencies. The submission
1822 and completion latencies then measure local time spent
1823 sending or receiving, and the completion latency measures
1824 how long it took for the other end to receive and send back.
1825 For UDP multicast traffic pingpong=1 should only be set for a
1826 single reader when multiple readers are listening to the same
1829 [net] window_size Set the desired socket buffer size for the connection.
1831 [net] mss Set the TCP maximum segment size (TCP_MAXSEG).
1833 [e4defrag] donorname=str
1834 File will be used as a block donor(swap extents between files)
1835 [e4defrag] inplace=int
1836 Configure donor file blocks allocation strategy
1837 0(default): Preallocate donor's file on init
1838 1 : allocate space immidietly inside defragment event,
1839 and free right after event
1841 [mtd] skip_bad=bool Skip operations against known bad blocks.
1844 6.0 Interpreting the output
1845 ---------------------------
1847 fio spits out a lot of output. While running, fio will display the
1848 status of the jobs created. An example of that would be:
1850 Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
1852 The characters inside the square brackets denote the current status of
1853 each thread. The possible values (in typical life cycle order) are:
1857 P Thread setup, but not started.
1859 I Thread initialized, waiting or generating necessary data.
1860 p Thread running pre-reading file(s).
1861 R Running, doing sequential reads.
1862 r Running, doing random reads.
1863 W Running, doing sequential writes.
1864 w Running, doing random writes.
1865 M Running, doing mixed sequential reads/writes.
1866 m Running, doing mixed random reads/writes.
1867 F Running, currently waiting for fsync()
1868 f Running, finishing up (writing IO logs, etc)
1869 V Running, doing verification of written data.
1870 E Thread exited, not reaped by main thread yet.
1872 X Thread reaped, exited with an error.
1873 K Thread reaped, exited due to signal.
1875 Fio will condense the thread string as not to take up more space on the
1876 command line as is needed. For instance, if you have 10 readers and 10
1877 writers running, the output would look like this:
1879 Jobs: 20 (f=20): [R(10),W(10)] [4.0% done] [2103MB/0KB/0KB /s] [538K/0/0 iops] [eta 57m:36s]
1881 Fio will still maintain the ordering, though. So the above means that jobs
1882 1..10 are readers, and 11..20 are writers.
1884 The other values are fairly self explanatory - number of threads
1885 currently running and doing io, rate of io since last check (read speed
1886 listed first, then write speed), and the estimated completion percentage
1887 and time for the running group. It's impossible to estimate runtime of
1888 the following groups (if any). Note that the string is displayed in order,
1889 so it's possible to tell which of the jobs are currently doing what. The
1890 first character is the first job defined in the job file, and so forth.
1892 When fio is done (or interrupted by ctrl-c), it will show the data for
1893 each thread, group of threads, and disks in that order. For each data
1894 direction, the output looks like:
1896 Client1 (g=0): err= 0:
1897 write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec
1898 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
1899 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
1900 bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
1901 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17
1902 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
1903 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1904 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1905 issued r/w: total=0/32768, short=0/0
1906 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
1907 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
1909 The client number is printed, along with the group id and error of that
1910 thread. Below is the io statistics, here for writes. In the order listed,
1913 io= Number of megabytes io performed
1914 bw= Average bandwidth rate
1915 iops= Average IOs performed per second
1916 runt= The runtime of that thread
1917 slat= Submission latency (avg being the average, stdev being the
1918 standard deviation). This is the time it took to submit
1919 the io. For sync io, the slat is really the completion
1920 latency, since queue/complete is one operation there. This
1921 value can be in milliseconds or microseconds, fio will choose
1922 the most appropriate base and print that. In the example
1923 above, milliseconds is the best scale. Note: in --minimal mode
1924 latencies are always expressed in microseconds.
1925 clat= Completion latency. Same names as slat, this denotes the
1926 time from submission to completion of the io pieces. For
1927 sync io, clat will usually be equal (or very close) to 0,
1928 as the time from submit to complete is basically just
1929 CPU time (io has already been done, see slat explanation).
1930 bw= Bandwidth. Same names as the xlat stats, but also includes
1931 an approximate percentage of total aggregate bandwidth
1932 this thread received in this group. This last value is
1933 only really useful if the threads in this group are on the
1934 same disk, since they are then competing for disk access.
1935 cpu= CPU usage. User and system time, along with the number
1936 of context switches this thread went through, usage of
1937 system and user time, and finally the number of major
1938 and minor page faults.
1939 IO depths= The distribution of io depths over the job life time. The
1940 numbers are divided into powers of 2, so for example the
1941 16= entries includes depths up to that value but higher
1942 than the previous entry. In other words, it covers the
1943 range from 16 to 31.
1944 IO submit= How many pieces of IO were submitting in a single submit
1945 call. Each entry denotes that amount and below, until
1946 the previous entry - eg, 8=100% mean that we submitted
1947 anywhere in between 5-8 ios per submit call.
1948 IO complete= Like the above submit number, but for completions instead.
1949 IO issued= The number of read/write requests issued, and how many
1951 IO latencies= The distribution of IO completion latencies. This is the
1952 time from when IO leaves fio and when it gets completed.
1953 The numbers follow the same pattern as the IO depths,
1954 meaning that 2=1.6% means that 1.6% of the IO completed
1955 within 2 msecs, 20=12.8% means that 12.8% of the IO
1956 took more than 10 msecs, but less than (or equal to) 20 msecs.
1958 After each client has been listed, the group statistics are printed. They
1959 will look like this:
1961 Run status group 0 (all jobs):
1962 READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
1963 WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
1965 For each data direction, it prints:
1967 io= Number of megabytes io performed.
1968 aggrb= Aggregate bandwidth of threads in this group.
1969 minb= The minimum average bandwidth a thread saw.
1970 maxb= The maximum average bandwidth a thread saw.
1971 mint= The smallest runtime of the threads in that group.
1972 maxt= The longest runtime of the threads in that group.
1974 And finally, the disk statistics are printed. They will look like this:
1976 Disk stats (read/write):
1977 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
1979 Each value is printed for both reads and writes, with reads first. The
1982 ios= Number of ios performed by all groups.
1983 merge= Number of merges io the io scheduler.
1984 ticks= Number of ticks we kept the disk busy.
1985 io_queue= Total time spent in the disk queue.
1986 util= The disk utilization. A value of 100% means we kept the disk
1987 busy constantly, 50% would be a disk idling half of the time.
1989 It is also possible to get fio to dump the current output while it is
1990 running, without terminating the job. To do that, send fio the USR1 signal.
1991 You can also get regularly timed dumps by using the --status-interval
1992 parameter, or by creating a file in /tmp named fio-dump-status. If fio
1993 sees this file, it will unlink it and dump the current output status.
1999 For scripted usage where you typically want to generate tables or graphs
2000 of the results, fio can output the results in a semicolon separated format.
2001 The format is one long line of values, such as:
2003 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%
2004 A description of this job goes here.
2006 The job description (if provided) follows on a second line.
2008 To enable terse output, use the --minimal command line option. The first
2009 value is the version of the terse output format. If the output has to
2010 be changed for some reason, this number will be incremented by 1 to
2011 signify that change.
2013 Split up, the format is as follows:
2015 terse version, fio version, jobname, groupid, error
2017 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
2018 Submission latency: min, max, mean, stdev (usec)
2019 Completion latency: min, max, mean, stdev (usec)
2020 Completion latency percentiles: 20 fields (see below)
2021 Total latency: min, max, mean, stdev (usec)
2022 Bw (KB/s): min, max, aggregate percentage of total, mean, stdev
2024 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
2025 Submission latency: min, max, mean, stdev (usec)
2026 Completion latency: min, max, mean, stdev(usec)
2027 Completion latency percentiles: 20 fields (see below)
2028 Total latency: min, max, mean, stdev (usec)
2029 Bw (KB/s): min, max, aggregate percentage of total, mean, stdev
2030 CPU usage: user, system, context switches, major faults, minor faults
2031 IO depths: <=1, 2, 4, 8, 16, 32, >=64
2032 IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
2033 IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
2034 Disk utilization: Disk name, Read ios, write ios,
2035 Read merges, write merges,
2036 Read ticks, write ticks,
2037 Time spent in queue, disk utilization percentage
2038 Additional Info (dependent on continue_on_error, default off): total # errors, first error code
2040 Additional Info (dependent on description being set): Text description
2042 Completion latency percentiles can be a grouping of up to 20 sets, so
2043 for the terse output fio writes all of them. Each field will look like this:
2047 which is the Xth percentile, and the usec latency associated with it.
2049 For disk utilization, all disks used by fio are shown. So for each disk
2050 there will be a disk utilization section.
2053 8.0 Trace file format
2054 ---------------------
2055 There are two trace file format that you can encounter. The older (v1) format
2056 is unsupported since version 1.20-rc3 (March 2008). It will still be described
2057 below in case that you get an old trace and want to understand it.
2059 In any case the trace is a simple text file with a single action per line.
2062 8.1 Trace file format v1
2063 ------------------------
2064 Each line represents a single io action in the following format:
2068 where rw=0/1 for read/write, and the offset and length entries being in bytes.
2070 This format is not supported in Fio versions => 1.20-rc3.
2073 8.2 Trace file format v2
2074 ------------------------
2075 The second version of the trace file format was added in Fio version 1.17.
2076 It allows to access more then one file per trace and has a bigger set of
2077 possible file actions.
2079 The first line of the trace file has to be:
2083 Following this can be lines in two different formats, which are described below.
2085 The file management format:
2089 The filename is given as an absolute path. The action can be one of these:
2091 add Add the given filename to the trace
2092 open Open the file with the given filename. The filename has to have
2093 been added with the add action before.
2094 close Close the file with the given filename. The file has to have been
2098 The file io action format:
2100 filename action offset length
2102 The filename is given as an absolute path, and has to have been added and opened
2103 before it can be used with this format. The offset and length are given in
2104 bytes. The action can be one of these:
2106 wait Wait for 'offset' microseconds. Everything below 100 is discarded.
2107 The time is relative to the previous wait statement.
2108 read Read 'length' bytes beginning from 'offset'
2109 write Write 'length' bytes beginning from 'offset'
2110 sync fsync() the file
2111 datasync fdatasync() the file
2112 trim trim the given file from the given 'offset' for 'length' bytes
2115 9.0 CPU idleness profiling
2116 --------------------------
2117 In some cases, we want to understand CPU overhead in a test. For example,
2118 we test patches for the specific goodness of whether they reduce CPU usage.
2119 fio implements a balloon approach to create a thread per CPU that runs at
2120 idle priority, meaning that it only runs when nobody else needs the cpu.
2121 By measuring the amount of work completed by the thread, idleness of each
2122 CPU can be derived accordingly.
2124 An unit work is defined as touching a full page of unsigned characters. Mean
2125 and standard deviation of time to complete an unit work is reported in "unit
2126 work" section. Options can be chosen to report detailed percpu idleness or
2127 overall system idleness by aggregating percpu stats.
2130 10.0 Verification and triggers
2131 ------------------------------
2132 Fio is usually run in one of two ways, when data verification is done. The
2133 first is a normal write job of some sort with verify enabled. When the
2134 write phase has completed, fio switches to reads and verifies everything
2135 it wrote. The second model is running just the write phase, and then later
2136 on running the same job (but with reads instead of writes) to repeat the
2137 same IO patterns and verify the contents. Both of these methods depend
2138 on the write phase being completed, as fio otherwise has no idea how much
2141 With verification triggers, fio supports dumping the current write state
2142 to local files. Then a subsequent read verify workload can load this state
2143 and know exactly where to stop. This is useful for testing cases where
2144 power is cut to a server in a managed fashion, for instance.
2146 A verification trigger consists of two things:
2148 1) Storing the write state of each job
2149 2) Executing a trigger command
2151 The write state is relatively small, on the order of hundreds of bytes
2152 to single kilobytes. It contains information on the number of completions
2153 done, the last X completions, etc.
2155 A trigger is invoked either through creation ('touch') of a specified
2156 file in the system, or through a timeout setting. If fio is run with
2157 --trigger-file=/tmp/trigger-file, then it will continually check for
2158 the existence of /tmp/trigger-file. When it sees this file, it will
2159 fire off the trigger (thus saving state, and executing the trigger
2162 For client/server runs, there's both a local and remote trigger. If
2163 fio is running as a server backend, it will send the job states back
2164 to the client for safe storage, then execute the remote trigger, if
2165 specified. If a local trigger is specified, the server will still send
2166 back the write state, but the client will then execute the trigger.
2168 10.1 Verification trigger example
2169 ---------------------------------
2170 Lets say we want to run a powercut test on the remote machine 'server'.
2171 Our write workload is in write-test.fio. We want to cut power to 'server'
2172 at some point during the run, and we'll run this test from the safety
2173 or our local machine, 'localbox'. On the server, we'll start the fio
2176 server# fio --server
2178 and on the client, we'll fire off the workload:
2180 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
2182 We set /tmp/my-trigger as the trigger file, and we tell fio to execute
2184 echo b > /proc/sysrq-trigger
2186 on the server once it has received the trigger and sent us the write
2187 state. This will work, but it's not _really_ cutting power to the server,
2188 it's merely abruptly rebooting it. If we have a remote way of cutting
2189 power to the server through IPMI or similar, we could do that through
2190 a local trigger command instead. Lets assume we have a script that does
2191 IPMI reboot of a given hostname, ipmi-reboot. On localbox, we could
2192 then have run fio with a local trigger instead:
2194 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
2196 For this case, fio would wait for the server to send us the write state,
2197 then execute 'ipmi-reboot server' when that happened.
2199 10.1 Loading verify state
2200 -------------------------
2201 To load store write state, read verification job file must contain
2202 the verify_state_load option. If that is set, fio will load the previously
2203 stored state. For a local fio run this is done by loading the files directly,
2204 and on a client/server run, the server backend will ask the client to send
2205 the files over and load them from there.