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 This engine interprets offsets a little
771 differently. In HDFS, files once created
772 cannot be modified. So random writes are not
773 possible. To imitate this, libhdfs engine
774 creates bunch of small files, and engine will
775 pick a file out of those files based on the
776 offset enerated by fio backend. Each jobs uses
777 it's own connection to HDFS.
779 mtd Read, write and erase an MTD character device
780 (e.g., /dev/mtd0). Discards are treated as
781 erases. Depending on the underlying device
782 type, the I/O may have to go in a certain
783 pattern, e.g., on NAND, writing sequentially
784 to erase blocks and discarding before
785 overwriting. The writetrim mode works well
788 external Prefix to specify loading an external
789 IO engine object file. Append the engine
790 filename, eg ioengine=external:/tmp/foo.o
791 to load ioengine foo.o in /tmp.
793 iodepth=int This defines how many io units to keep in flight against
794 the file. The default is 1 for each file defined in this
795 job, can be overridden with a larger value for higher
796 concurrency. Note that increasing iodepth beyond 1 will not
797 affect synchronous ioengines (except for small degress when
798 verify_async is in use). Even async engines may impose OS
799 restrictions causing the desired depth not to be achieved.
800 This may happen on Linux when using libaio and not setting
801 direct=1, since buffered IO is not async on that OS. Keep an
802 eye on the IO depth distribution in the fio output to verify
803 that the achieved depth is as expected. Default: 1.
805 iodepth_batch_submit=int
806 iodepth_batch=int This defines how many pieces of IO to submit at once.
807 It defaults to 1 which means that we submit each IO
808 as soon as it is available, but can be raised to submit
809 bigger batches of IO at the time. If it is set to 0 the iodepth
812 iodepth_batch_complete_min=int
813 iodepth_batch_complete=int This defines how many pieces of IO to retrieve
814 at once. It defaults to 1 which means that we'll ask
815 for a minimum of 1 IO in the retrieval process from
816 the kernel. The IO retrieval will go on until we
817 hit the limit set by iodepth_low. If this variable is
818 set to 0, then fio will always check for completed
819 events before queuing more IO. This helps reduce
820 IO latency, at the cost of more retrieval system calls.
822 iodepth_batch_complete_max=int This defines maximum pieces of IO to
823 retrieve at once. This variable should be used along with
824 iodepth_batch_complete_min=int variable, specifying the range
825 of min and max amount of IO which should be retrieved. By default
826 it is equal to iodepth_batch_complete_min value.
830 iodepth_batch_complete_min=1
831 iodepth_batch_complete_max=<iodepth>
833 which means that we will retrieve at leat 1 IO and up to the
834 whole submitted queue depth. If none of IO has been completed
839 iodepth_batch_complete_min=0
840 iodepth_batch_complete_max=<iodepth>
842 which means that we can retrieve up to the whole submitted
843 queue depth, but if none of IO has been completed yet, we will
844 NOT wait and immediately exit the system call. In this example
845 we simply do polling.
847 iodepth_low=int The low water mark indicating when to start filling
848 the queue again. Defaults to the same as iodepth, meaning
849 that fio will attempt to keep the queue full at all times.
850 If iodepth is set to eg 16 and iodepth_low is set to 4, then
851 after fio has filled the queue of 16 requests, it will let
852 the depth drain down to 4 before starting to fill it again.
854 io_submit_mode=str This option controls how fio submits the IO to
855 the IO engine. The default is 'inline', which means that the
856 fio job threads submit and reap IO directly. If set to
857 'offload', the job threads will offload IO submission to a
858 dedicated pool of IO threads. This requires some coordination
859 and thus has a bit of extra overhead, especially for lower
860 queue depth IO where it can increase latencies. The benefit
861 is that fio can manage submission rates independently of
862 the device completion rates. This avoids skewed latency
863 reporting if IO gets back up on the device side (the
864 coordinated omission problem).
866 direct=bool If value is true, use non-buffered io. This is usually
867 O_DIRECT. Note that ZFS on Solaris doesn't support direct io.
868 On Windows the synchronous ioengines don't support direct io.
870 atomic=bool If value is true, attempt to use atomic direct IO. Atomic
871 writes are guaranteed to be stable once acknowledged by
872 the operating system. Only Linux supports O_ATOMIC right
875 buffered=bool If value is true, use buffered io. This is the opposite
876 of the 'direct' option. Defaults to true.
878 offset=int Start io at the given offset in the file. The data before
879 the given offset will not be touched. This effectively
880 caps the file size at real_size - offset.
882 offset_increment=int If this is provided, then the real offset becomes
883 offset + offset_increment * thread_number, where the thread
884 number is a counter that starts at 0 and is incremented for
885 each sub-job (i.e. when numjobs option is specified). This
886 option is useful if there are several jobs which are intended
887 to operate on a file in parallel disjoint segments, with
888 even spacing between the starting points.
890 number_ios=int Fio will normally perform IOs until it has exhausted the size
891 of the region set by size=, or if it exhaust the allocated
892 time (or hits an error condition). With this setting, the
893 range/size can be set independently of the number of IOs to
894 perform. When fio reaches this number, it will exit normally
895 and report status. Note that this does not extend the amount
896 of IO that will be done, it will only stop fio if this
897 condition is met before other end-of-job criteria.
899 fsync=int If writing to a file, issue a sync of the dirty data
900 for every number of blocks given. For example, if you give
901 32 as a parameter, fio will sync the file for every 32
902 writes issued. If fio is using non-buffered io, we may
903 not sync the file. The exception is the sg io engine, which
904 synchronizes the disk cache anyway.
906 fdatasync=int Like fsync= but uses fdatasync() to only sync data and not
908 In FreeBSD and Windows there is no fdatasync(), this falls back
911 sync_file_range=str:val Use sync_file_range() for every 'val' number of
912 write operations. Fio will track range of writes that
913 have happened since the last sync_file_range() call. 'str'
914 can currently be one or more of:
916 wait_before SYNC_FILE_RANGE_WAIT_BEFORE
917 write SYNC_FILE_RANGE_WRITE
918 wait_after SYNC_FILE_RANGE_WAIT_AFTER
920 So if you do sync_file_range=wait_before,write:8, fio would
921 use SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE for
922 every 8 writes. Also see the sync_file_range(2) man page.
923 This option is Linux specific.
925 overwrite=bool If true, writes to a file will always overwrite existing
926 data. If the file doesn't already exist, it will be
927 created before the write phase begins. If the file exists
928 and is large enough for the specified write phase, nothing
931 end_fsync=bool If true, fsync file contents when a write stage has completed.
933 fsync_on_close=bool If true, fio will fsync() a dirty file on close.
934 This differs from end_fsync in that it will happen on every
935 file close, not just at the end of the job.
937 rwmixread=int How large a percentage of the mix should be reads.
939 rwmixwrite=int How large a percentage of the mix should be writes. If both
940 rwmixread and rwmixwrite is given and the values do not add
941 up to 100%, the latter of the two will be used to override
942 the first. This may interfere with a given rate setting,
943 if fio is asked to limit reads or writes to a certain rate.
944 If that is the case, then the distribution may be skewed.
946 random_distribution=str:float By default, fio will use a completely uniform
947 random distribution when asked to perform random IO. Sometimes
948 it is useful to skew the distribution in specific ways,
949 ensuring that some parts of the data is more hot than others.
950 fio includes the following distribution models:
952 random Uniform random distribution
953 zipf Zipf distribution
954 pareto Pareto distribution
956 When using a zipf or pareto distribution, an input value
957 is also needed to define the access pattern. For zipf, this
958 is the zipf theta. For pareto, it's the pareto power. Fio
959 includes a test program, genzipf, that can be used visualize
960 what the given input values will yield in terms of hit rates.
961 If you wanted to use zipf with a theta of 1.2, you would use
962 random_distribution=zipf:1.2 as the option. If a non-uniform
963 model is used, fio will disable use of the random map.
965 percentage_random=int For a random workload, set how big a percentage should
966 be random. This defaults to 100%, in which case the workload
967 is fully random. It can be set from anywhere from 0 to 100.
968 Setting it to 0 would make the workload fully sequential. Any
969 setting in between will result in a random mix of sequential
970 and random IO, at the given percentages. It is possible to
971 set different values for reads, writes, and trim. To do so,
972 simply use a comma separated list. See blocksize.
974 norandommap Normally fio will cover every block of the file when doing
975 random IO. If this option is given, fio will just get a
976 new random offset without looking at past io history. This
977 means that some blocks may not be read or written, and that
978 some blocks may be read/written more than once. If this option
979 is used with verify= and multiple blocksizes (via bsrange=),
980 only intact blocks are verified, i.e., partially-overwritten
983 softrandommap=bool See norandommap. If fio runs with the random block map
984 enabled and it fails to allocate the map, if this option is
985 set it will continue without a random block map. As coverage
986 will not be as complete as with random maps, this option is
989 random_generator=str Fio supports the following engines for generating
990 IO offsets for random IO:
992 tausworthe Strong 2^88 cycle random number generator
993 lfsr Linear feedback shift register generator
994 tausworthe64 Strong 64-bit 2^258 cycle random number
997 Tausworthe is a strong random number generator, but it
998 requires tracking on the side if we want to ensure that
999 blocks are only read or written once. LFSR guarantees
1000 that we never generate the same offset twice, and it's
1001 also less computationally expensive. It's not a true
1002 random generator, however, though for IO purposes it's
1003 typically good enough. LFSR only works with single
1004 block sizes, not with workloads that use multiple block
1005 sizes. If used with such a workload, fio may read or write
1006 some blocks multiple times.
1008 nice=int Run the job with the given nice value. See man nice(2).
1010 prio=int Set the io priority value of this job. Linux limits us to
1011 a positive value between 0 and 7, with 0 being the highest.
1014 prioclass=int Set the io priority class. See man ionice(1).
1016 thinktime=int Stall the job x microseconds after an io has completed before
1017 issuing the next. May be used to simulate processing being
1018 done by an application. See thinktime_blocks and
1022 Only valid if thinktime is set - pretend to spend CPU time
1023 doing something with the data received, before falling back
1024 to sleeping for the rest of the period specified by
1027 thinktime_blocks=int
1028 Only valid if thinktime is set - control how many blocks
1029 to issue, before waiting 'thinktime' usecs. If not set,
1030 defaults to 1 which will make fio wait 'thinktime' usecs
1031 after every block. This effectively makes any queue depth
1032 setting redundant, since no more than 1 IO will be queued
1033 before we have to complete it and do our thinktime. In
1034 other words, this setting effectively caps the queue depth
1035 if the latter is larger.
1037 rate=int Cap the bandwidth used by this job. The number is in bytes/sec,
1038 the normal suffix rules apply. You can use rate=500k to limit
1039 reads and writes to 500k each, or you can specify read and
1040 writes separately. Using rate=1m,500k would limit reads to
1041 1MB/sec and writes to 500KB/sec. Capping only reads or
1042 writes can be done with rate=,500k or rate=500k,. The former
1043 will only limit writes (to 500KB/sec), the latter will only
1046 rate_min=int Tell fio to do whatever it can to maintain at least this
1047 bandwidth. Failing to meet this requirement, will cause
1048 the job to exit. The same format as rate is used for
1049 read vs write separation.
1051 rate_iops=int Cap the bandwidth to this number of IOPS. Basically the same
1052 as rate, just specified independently of bandwidth. If the
1053 job is given a block size range instead of a fixed value,
1054 the smallest block size is used as the metric. The same format
1055 as rate is used for read vs write separation.
1057 rate_iops_min=int If fio doesn't meet this rate of IO, it will cause
1058 the job to exit. The same format as rate is used for read vs
1061 rate_process=str This option controls how fio manages rated IO
1062 submissions. The default is 'linear', which submits IO in a
1063 linear fashion with fixed delays between IOs that gets
1064 adjusted based on IO completion rates. If this is set to
1065 'poisson', fio will submit IO based on a more real world
1066 random request flow, known as the Poisson process
1067 (https://en.wikipedia.org/wiki/Poisson_process). The lambda
1068 will be 10^6 / IOPS for the given workload.
1070 latency_target=int If set, fio will attempt to find the max performance
1071 point that the given workload will run at while maintaining a
1072 latency below this target. The values is given in microseconds.
1073 See latency_window and latency_percentile
1075 latency_window=int Used with latency_target to specify the sample window
1076 that the job is run at varying queue depths to test the
1077 performance. The value is given in microseconds.
1079 latency_percentile=float The percentage of IOs that must fall within the
1080 criteria specified by latency_target and latency_window. If not
1081 set, this defaults to 100.0, meaning that all IOs must be equal
1082 or below to the value set by latency_target.
1084 max_latency=int If set, fio will exit the job if it exceeds this maximum
1085 latency. It will exit with an ETIME error.
1087 rate_cycle=int Average bandwidth for 'rate' and 'rate_min' over this number
1090 cpumask=int Set the CPU affinity of this job. The parameter given is a
1091 bitmask of allowed CPU's the job may run on. So if you want
1092 the allowed CPUs to be 1 and 5, you would pass the decimal
1093 value of (1 << 1 | 1 << 5), or 34. See man
1094 sched_setaffinity(2). This may not work on all supported
1095 operating systems or kernel versions. This option doesn't
1096 work well for a higher CPU count than what you can store in
1097 an integer mask, so it can only control cpus 1-32. For
1098 boxes with larger CPU counts, use cpus_allowed.
1100 cpus_allowed=str Controls the same options as cpumask, but it allows a text
1101 setting of the permitted CPUs instead. So to use CPUs 1 and
1102 5, you would specify cpus_allowed=1,5. This options also
1103 allows a range of CPUs. Say you wanted a binding to CPUs
1104 1, 5, and 8-15, you would set cpus_allowed=1,5,8-15.
1106 cpus_allowed_policy=str Set the policy of how fio distributes the CPUs
1107 specified by cpus_allowed or cpumask. Two policies are
1110 shared All jobs will share the CPU set specified.
1111 split Each job will get a unique CPU from the CPU set.
1113 'shared' is the default behaviour, if the option isn't
1114 specified. If split is specified, then fio will will assign
1115 one cpu per job. If not enough CPUs are given for the jobs
1116 listed, then fio will roundrobin the CPUs in the set.
1118 numa_cpu_nodes=str Set this job running on spcified NUMA nodes' CPUs. The
1119 arguments allow comma delimited list of cpu numbers,
1120 A-B ranges, or 'all'. Note, to enable numa options support,
1121 fio must be built on a system with libnuma-dev(el) installed.
1123 numa_mem_policy=str Set this job's memory policy and corresponding NUMA
1124 nodes. Format of the argements:
1126 `mode' is one of the following memory policy:
1127 default, prefer, bind, interleave, local
1128 For `default' and `local' memory policy, no node is
1129 needed to be specified.
1130 For `prefer', only one node is allowed.
1131 For `bind' and `interleave', it allow comma delimited
1132 list of numbers, A-B ranges, or 'all'.
1134 startdelay=time Start this job the specified number of seconds after fio
1135 has started. Only useful if the job file contains several
1136 jobs, and you want to delay starting some jobs to a certain
1139 runtime=time Tell fio to terminate processing after the specified number
1140 of seconds. It can be quite hard to determine for how long
1141 a specified job will run, so this parameter is handy to
1142 cap the total runtime to a given time.
1144 time_based If set, fio will run for the duration of the runtime
1145 specified even if the file(s) are completely read or
1146 written. It will simply loop over the same workload
1147 as many times as the runtime allows.
1149 ramp_time=time If set, fio will run the specified workload for this amount
1150 of time before logging any performance numbers. Useful for
1151 letting performance settle before logging results, thus
1152 minimizing the runtime required for stable results. Note
1153 that the ramp_time is considered lead in time for a job,
1154 thus it will increase the total runtime if a special timeout
1155 or runtime is specified.
1157 invalidate=bool Invalidate the buffer/page cache parts for this file prior
1158 to starting io. Defaults to true.
1160 sync=bool Use sync io for buffered writes. For the majority of the
1161 io engines, this means using O_SYNC.
1164 mem=str Fio can use various types of memory as the io unit buffer.
1165 The allowed values are:
1167 malloc Use memory from malloc(3) as the buffers.
1169 shm Use shared memory as the buffers. Allocated
1172 shmhuge Same as shm, but use huge pages as backing.
1174 mmap Use mmap to allocate buffers. May either be
1175 anonymous memory, or can be file backed if
1176 a filename is given after the option. The
1177 format is mem=mmap:/path/to/file.
1179 mmaphuge Use a memory mapped huge file as the buffer
1180 backing. Append filename after mmaphuge, ala
1181 mem=mmaphuge:/hugetlbfs/file
1183 mmapshared Same as mmap, but use a MMAP_SHARED
1186 The area allocated is a function of the maximum allowed
1187 bs size for the job, multiplied by the io depth given. Note
1188 that for shmhuge and mmaphuge to work, the system must have
1189 free huge pages allocated. This can normally be checked
1190 and set by reading/writing /proc/sys/vm/nr_hugepages on a
1191 Linux system. Fio assumes a huge page is 4MB in size. So
1192 to calculate the number of huge pages you need for a given
1193 job file, add up the io depth of all jobs (normally one unless
1194 iodepth= is used) and multiply by the maximum bs set. Then
1195 divide that number by the huge page size. You can see the
1196 size of the huge pages in /proc/meminfo. If no huge pages
1197 are allocated by having a non-zero number in nr_hugepages,
1198 using mmaphuge or shmhuge will fail. Also see hugepage-size.
1200 mmaphuge also needs to have hugetlbfs mounted and the file
1201 location should point there. So if it's mounted in /huge,
1202 you would use mem=mmaphuge:/huge/somefile.
1204 iomem_align=int This indiciates the memory alignment of the IO memory buffers.
1205 Note that the given alignment is applied to the first IO unit
1206 buffer, if using iodepth the alignment of the following buffers
1207 are given by the bs used. In other words, if using a bs that is
1208 a multiple of the page sized in the system, all buffers will
1209 be aligned to this value. If using a bs that is not page
1210 aligned, the alignment of subsequent IO memory buffers is the
1211 sum of the iomem_align and bs used.
1214 Defines the size of a huge page. Must at least be equal
1215 to the system setting, see /proc/meminfo. Defaults to 4MB.
1216 Should probably always be a multiple of megabytes, so using
1217 hugepage-size=Xm is the preferred way to set this to avoid
1218 setting a non-pow-2 bad value.
1220 exitall When one job finishes, terminate the rest. The default is
1221 to wait for each job to finish, sometimes that is not the
1224 exitall_on_error When one job finishes in error, terminate the rest. The
1225 default is to wait for each job to finish.
1227 bwavgtime=int Average the calculated bandwidth over the given time. Value
1228 is specified in milliseconds.
1230 iopsavgtime=int Average the calculated IOPS over the given time. Value
1231 is specified in milliseconds.
1233 create_serialize=bool If true, serialize the file creating for the jobs.
1234 This may be handy to avoid interleaving of data
1235 files, which may greatly depend on the filesystem
1236 used and even the number of processors in the system.
1238 create_fsync=bool fsync the data file after creation. This is the
1241 create_on_open=bool Don't pre-setup the files for IO, just create open()
1242 when it's time to do IO to that file.
1244 create_only=bool If true, fio will only run the setup phase of the job.
1245 If files need to be laid out or updated on disk, only
1246 that will be done. The actual job contents are not
1249 allow_file_create=bool If true, fio is permitted to create files as part
1250 of its workload. This is the default behavior. If this
1251 option is false, then fio will error out if the files it
1252 needs to use don't already exist. Default: true.
1254 allow_mounted_write=bool If this isn't set, fio will abort jobs that
1255 are destructive (eg that write) to what appears to be a
1256 mounted device or partition. This should help catch creating
1257 inadvertently destructive tests, not realizing that the test
1258 will destroy data on the mounted file system. Default: false.
1260 pre_read=bool If this is given, files will be pre-read into memory before
1261 starting the given IO operation. This will also clear
1262 the 'invalidate' flag, since it is pointless to pre-read
1263 and then drop the cache. This will only work for IO engines
1264 that are seekable, since they allow you to read the same data
1265 multiple times. Thus it will not work on eg network or splice
1268 unlink=bool Unlink the job files when done. Not the default, as repeated
1269 runs of that job would then waste time recreating the file
1270 set again and again.
1272 loops=int Run the specified number of iterations of this job. Used
1273 to repeat the same workload a given number of times. Defaults
1276 verify_only Do not perform specified workload---only verify data still
1277 matches previous invocation of this workload. This option
1278 allows one to check data multiple times at a later date
1279 without overwriting it. This option makes sense only for
1280 workloads that write data, and does not support workloads
1281 with the time_based option set.
1283 do_verify=bool Run the verify phase after a write phase. Only makes sense if
1284 verify is set. Defaults to 1.
1286 verify=str If writing to a file, fio can verify the file contents
1287 after each iteration of the job. Each verification method also implies
1288 verification of special header, which is written to the beginning of
1289 each block. This header also includes meta information, like offset
1290 of the block, block number, timestamp when block was written, etc.
1291 verify=str can be combined with verify_pattern=str option.
1292 The allowed values are:
1294 md5 Use an md5 sum of the data area and store
1295 it in the header of each block.
1297 crc64 Use an experimental crc64 sum of the data
1298 area and store it in the header of each
1301 crc32c Use a crc32c sum of the data area and store
1302 it in the header of each block.
1304 crc32c-intel Use hardware assisted crc32c calcuation
1305 provided on SSE4.2 enabled processors. Falls
1306 back to regular software crc32c, if not
1307 supported by the system.
1309 crc32 Use a crc32 sum of the data area and store
1310 it in the header of each block.
1312 crc16 Use a crc16 sum of the data area and store
1313 it in the header of each block.
1315 crc7 Use a crc7 sum of the data area and store
1316 it in the header of each block.
1318 xxhash Use xxhash as the checksum function. Generally
1319 the fastest software checksum that fio
1322 sha512 Use sha512 as the checksum function.
1324 sha256 Use sha256 as the checksum function.
1326 sha1 Use optimized sha1 as the checksum function.
1328 meta This option is deprecated, since now meta information is
1329 included in generic verification header and meta verification
1330 happens by default. For detailed information see the description
1331 of the verify=str setting. This option is kept because of
1332 compatibility's sake with old configurations. Do not use it.
1334 pattern Verify a strict pattern. Normally fio includes
1335 a header with some basic information and
1336 checksumming, but if this option is set, only
1337 the specific pattern set with 'verify_pattern'
1340 null Only pretend to verify. Useful for testing
1341 internals with ioengine=null, not for much
1344 This option can be used for repeated burn-in tests of a
1345 system to make sure that the written data is also
1346 correctly read back. If the data direction given is
1347 a read or random read, fio will assume that it should
1348 verify a previously written file. If the data direction
1349 includes any form of write, the verify will be of the
1352 verifysort=bool If set, fio will sort written verify blocks when it deems
1353 it faster to read them back in a sorted manner. This is
1354 often the case when overwriting an existing file, since
1355 the blocks are already laid out in the file system. You
1356 can ignore this option unless doing huge amounts of really
1357 fast IO where the red-black tree sorting CPU time becomes
1360 verify_offset=int Swap the verification header with data somewhere else
1361 in the block before writing. Its swapped back before
1364 verify_interval=int Write the verification header at a finer granularity
1365 than the blocksize. It will be written for chunks the
1366 size of header_interval. blocksize should divide this
1369 verify_pattern=str If set, fio will fill the io buffers with this
1370 pattern. Fio defaults to filling with totally random
1371 bytes, but sometimes it's interesting to fill with a known
1372 pattern for io verification purposes. Depending on the
1373 width of the pattern, fio will fill 1/2/3/4 bytes of the
1374 buffer at the time(it can be either a decimal or a hex number).
1375 The verify_pattern if larger than a 32-bit quantity has to
1376 be a hex number that starts with either "0x" or "0X". Use
1377 with verify=str. Also, verify_pattern supports %o format,
1378 which means that for each block offset will be written and
1379 then verifyied back, e.g.:
1383 Or use combination of everything:
1384 verify_pattern=0xff%o"abcd"-12
1386 verify_fatal=bool Normally fio will keep checking the entire contents
1387 before quitting on a block verification failure. If this
1388 option is set, fio will exit the job on the first observed
1391 verify_dump=bool If set, dump the contents of both the original data
1392 block and the data block we read off disk to files. This
1393 allows later analysis to inspect just what kind of data
1394 corruption occurred. Off by default.
1396 verify_async=int Fio will normally verify IO inline from the submitting
1397 thread. This option takes an integer describing how many
1398 async offload threads to create for IO verification instead,
1399 causing fio to offload the duty of verifying IO contents
1400 to one or more separate threads. If using this offload
1401 option, even sync IO engines can benefit from using an
1402 iodepth setting higher than 1, as it allows them to have
1403 IO in flight while verifies are running.
1405 verify_async_cpus=str Tell fio to set the given CPU affinity on the
1406 async IO verification threads. See cpus_allowed for the
1409 verify_backlog=int Fio will normally verify the written contents of a
1410 job that utilizes verify once that job has completed. In
1411 other words, everything is written then everything is read
1412 back and verified. You may want to verify continually
1413 instead for a variety of reasons. Fio stores the meta data
1414 associated with an IO block in memory, so for large
1415 verify workloads, quite a bit of memory would be used up
1416 holding this meta data. If this option is enabled, fio
1417 will write only N blocks before verifying these blocks.
1419 verify_backlog_batch=int Control how many blocks fio will verify
1420 if verify_backlog is set. If not set, will default to
1421 the value of verify_backlog (meaning the entire queue
1422 is read back and verified). If verify_backlog_batch is
1423 less than verify_backlog then not all blocks will be verified,
1424 if verify_backlog_batch is larger than verify_backlog, some
1425 blocks will be verified more than once.
1427 verify_state_save=bool When a job exits during the write phase of a verify
1428 workload, save its current state. This allows fio to replay
1429 up until that point, if the verify state is loaded for the
1430 verify read phase. The format of the filename is, roughly,
1431 <type>-<jobname>-<jobindex>-verify.state. <type> is "local"
1432 for a local run, "sock" for a client/server socket connection,
1433 and "ip" (192.168.0.1, for instance) for a networked
1434 client/server connection.
1436 verify_state_load=bool If a verify termination trigger was used, fio stores
1437 the current write state of each thread. This can be used at
1438 verification time so that fio knows how far it should verify.
1439 Without this information, fio will run a full verification
1440 pass, according to the settings in the job file used.
1443 wait_for_previous Wait for preceding jobs in the job file to exit, before
1444 starting this one. Can be used to insert serialization
1445 points in the job file. A stone wall also implies starting
1446 a new reporting group.
1448 new_group Start a new reporting group. See: group_reporting.
1450 numjobs=int Create the specified number of clones of this job. May be
1451 used to setup a larger number of threads/processes doing
1452 the same thing. Each thread is reported separately; to see
1453 statistics for all clones as a whole, use group_reporting in
1454 conjunction with new_group.
1456 group_reporting It may sometimes be interesting to display statistics for
1457 groups of jobs as a whole instead of for each individual job.
1458 This is especially true if 'numjobs' is used; looking at
1459 individual thread/process output quickly becomes unwieldy.
1460 To see the final report per-group instead of per-job, use
1461 'group_reporting'. Jobs in a file will be part of the same
1462 reporting group, unless if separated by a stonewall, or by
1465 thread fio defaults to forking jobs, however if this option is
1466 given, fio will use pthread_create(3) to create threads
1469 zonesize=int Divide a file into zones of the specified size. See zoneskip.
1471 zoneskip=int Skip the specified number of bytes when zonesize data has
1472 been read. The two zone options can be used to only do
1473 io on zones of a file.
1475 write_iolog=str Write the issued io patterns to the specified file. See
1476 read_iolog. Specify a separate file for each job, otherwise
1477 the iologs will be interspersed and the file may be corrupt.
1479 read_iolog=str Open an iolog with the specified file name and replay the
1480 io patterns it contains. This can be used to store a
1481 workload and replay it sometime later. The iolog given
1482 may also be a blktrace binary file, which allows fio
1483 to replay a workload captured by blktrace. See blktrace
1484 for how to capture such logging data. For blktrace replay,
1485 the file needs to be turned into a blkparse binary data
1486 file first (blkparse <device> -o /dev/null -d file_for_fio.bin).
1488 replay_no_stall=int When replaying I/O with read_iolog the default behavior
1489 is to attempt to respect the time stamps within the log and
1490 replay them with the appropriate delay between IOPS. By
1491 setting this variable fio will not respect the timestamps and
1492 attempt to replay them as fast as possible while still
1493 respecting ordering. The result is the same I/O pattern to a
1494 given device, but different timings.
1496 replay_redirect=str While replaying I/O patterns using read_iolog the
1497 default behavior is to replay the IOPS onto the major/minor
1498 device that each IOP was recorded from. This is sometimes
1499 undesirable because on a different machine those major/minor
1500 numbers can map to a different device. Changing hardware on
1501 the same system can also result in a different major/minor
1502 mapping. Replay_redirect causes all IOPS to be replayed onto
1503 the single specified device regardless of the device it was
1504 recorded from. i.e. replay_redirect=/dev/sdc would cause all
1505 IO in the blktrace to be replayed onto /dev/sdc. This means
1506 multiple devices will be replayed onto a single, if the trace
1507 contains multiple devices. If you want multiple devices to be
1508 replayed concurrently to multiple redirected devices you must
1509 blkparse your trace into separate traces and replay them with
1510 independent fio invocations. Unfortuantely this also breaks
1511 the strict time ordering between multiple device accesses.
1513 replay_align=int Force alignment of IO offsets and lengths in a trace
1514 to this power of 2 value.
1516 replay_scale=int Scale sector offsets down by this factor when
1519 per_job_logs=bool If set, this generates bw/clat/iops log with per
1520 file private filenames. If not set, jobs with identical names
1521 will share the log filename. Default: true.
1523 write_bw_log=str If given, write a bandwidth log of the jobs in this job
1524 file. Can be used to store data of the bandwidth of the
1525 jobs in their lifetime. The included fio_generate_plots
1526 script uses gnuplot to turn these text files into nice
1527 graphs. See write_lat_log for behaviour of given
1528 filename. For this option, the suffix is _bw.x.log, where
1529 x is the index of the job (1..N, where N is the number of
1530 jobs). If 'per_job_logs' is false, then the filename will not
1531 include the job index.
1533 write_lat_log=str Same as write_bw_log, except that this option stores io
1534 submission, completion, and total latencies instead. If no
1535 filename is given with this option, the default filename of
1536 "jobname_type.log" is used. Even if the filename is given,
1537 fio will still append the type of log. So if one specifies
1541 The actual log names will be foo_slat.x.log, foo_clat.x.log,
1542 and foo_lat.x.log, where x is the index of the job (1..N,
1543 where N is the number of jobs). This helps fio_generate_plot
1544 fine the logs automatically. If 'per_job_logs' is false, then
1545 the filename will not include the job index.
1548 write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is
1549 given with this option, the default filename of
1550 "jobname_type.x.log" is used,where x is the index of the job
1551 (1..N, where N is the number of jobs). Even if the filename
1552 is given, fio will still append the type of log. If
1553 'per_job_logs' is false, then the filename will not include
1556 log_avg_msec=int By default, fio will log an entry in the iops, latency,
1557 or bw log for every IO that completes. When writing to the
1558 disk log, that can quickly grow to a very large size. Setting
1559 this option makes fio average the each log entry over the
1560 specified period of time, reducing the resolution of the log.
1563 log_offset=int If this is set, the iolog options will include the byte
1564 offset for the IO entry as well as the other data values.
1566 log_compression=int If this is set, fio will compress the IO logs as
1567 it goes, to keep the memory footprint lower. When a log
1568 reaches the specified size, that chunk is removed and
1569 compressed in the background. Given that IO logs are
1570 fairly highly compressible, this yields a nice memory
1571 savings for longer runs. The downside is that the
1572 compression will consume some background CPU cycles, so
1573 it may impact the run. This, however, is also true if
1574 the logging ends up consuming most of the system memory.
1575 So pick your poison. The IO logs are saved normally at the
1576 end of a run, by decompressing the chunks and storing them
1577 in the specified log file. This feature depends on the
1578 availability of zlib.
1580 log_compression_cpus=str Define the set of CPUs that are allowed to
1581 handle online log compression for the IO jobs. This can
1582 provide better isolation between performance sensitive jobs,
1583 and background compression work.
1585 log_store_compressed=bool If set, fio will store the log files in a
1586 compressed format. They can be decompressed with fio, using
1587 the --inflate-log command line parameter. The files will be
1588 stored with a .fz suffix.
1590 block_error_percentiles=bool If set, record errors in trim block-sized
1591 units from writes and trims and output a histogram of
1592 how many trims it took to get to errors, and what kind
1593 of error was encountered.
1595 lockmem=int Pin down the specified amount of memory with mlock(2). Can
1596 potentially be used instead of removing memory or booting
1597 with less memory to simulate a smaller amount of memory.
1598 The amount specified is per worker.
1600 exec_prerun=str Before running this job, issue the command specified
1601 through system(3). Output is redirected in a file called
1604 exec_postrun=str After the job completes, issue the command specified
1605 though system(3). Output is redirected in a file called
1606 jobname.postrun.txt.
1608 ioscheduler=str Attempt to switch the device hosting the file to the specified
1609 io scheduler before running.
1611 disk_util=bool Generate disk utilization statistics, if the platform
1612 supports it. Defaults to on.
1614 disable_lat=bool Disable measurements of total latency numbers. Useful
1615 only for cutting back the number of calls to gettimeofday,
1616 as that does impact performance at really high IOPS rates.
1617 Note that to really get rid of a large amount of these
1618 calls, this option must be used with disable_slat and
1621 disable_clat=bool Disable measurements of completion latency numbers. See
1624 disable_slat=bool Disable measurements of submission latency numbers. See
1627 disable_bw=bool Disable measurements of throughput/bandwidth numbers. See
1630 clat_percentiles=bool Enable the reporting of percentiles of
1631 completion latencies.
1633 percentile_list=float_list Overwrite the default list of percentiles
1634 for completion latencies and the block error histogram.
1635 Each number is a floating number in the range (0,100],
1636 and the maximum length of the list is 20. Use ':'
1637 to separate the numbers, and list the numbers in ascending
1638 order. For example, --percentile_list=99.5:99.9 will cause
1639 fio to report the values of completion latency below which
1640 99.5% and 99.9% of the observed latencies fell, respectively.
1642 clocksource=str Use the given clocksource as the base of timing. The
1643 supported options are:
1645 gettimeofday gettimeofday(2)
1647 clock_gettime clock_gettime(2)
1649 cpu Internal CPU clock source
1651 cpu is the preferred clocksource if it is reliable, as it
1652 is very fast (and fio is heavy on time calls). Fio will
1653 automatically use this clocksource if it's supported and
1654 considered reliable on the system it is running on, unless
1655 another clocksource is specifically set. For x86/x86-64 CPUs,
1656 this means supporting TSC Invariant.
1658 gtod_reduce=bool Enable all of the gettimeofday() reducing options
1659 (disable_clat, disable_slat, disable_bw) plus reduce
1660 precision of the timeout somewhat to really shrink
1661 the gettimeofday() call count. With this option enabled,
1662 we only do about 0.4% of the gtod() calls we would have
1663 done if all time keeping was enabled.
1665 gtod_cpu=int Sometimes it's cheaper to dedicate a single thread of
1666 execution to just getting the current time. Fio (and
1667 databases, for instance) are very intensive on gettimeofday()
1668 calls. With this option, you can set one CPU aside for
1669 doing nothing but logging current time to a shared memory
1670 location. Then the other threads/processes that run IO
1671 workloads need only copy that segment, instead of entering
1672 the kernel with a gettimeofday() call. The CPU set aside
1673 for doing these time calls will be excluded from other
1674 uses. Fio will manually clear it from the CPU mask of other
1677 continue_on_error=str Normally fio will exit the job on the first observed
1678 failure. If this option is set, fio will continue the job when
1679 there is a 'non-fatal error' (EIO or EILSEQ) until the runtime
1680 is exceeded or the I/O size specified is completed. If this
1681 option is used, there are two more stats that are appended,
1682 the total error count and the first error. The error field
1683 given in the stats is the first error that was hit during the
1686 The allowed values are:
1688 none Exit on any IO or verify errors.
1690 read Continue on read errors, exit on all others.
1692 write Continue on write errors, exit on all others.
1694 io Continue on any IO error, exit on all others.
1696 verify Continue on verify errors, exit on all others.
1698 all Continue on all errors.
1700 0 Backward-compatible alias for 'none'.
1702 1 Backward-compatible alias for 'all'.
1704 ignore_error=str Sometimes you want to ignore some errors during test
1705 in that case you can specify error list for each error type.
1706 ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST
1707 errors for given error type is separated with ':'. Error
1708 may be symbol ('ENOSPC', 'ENOMEM') or integer.
1710 ignore_error=EAGAIN,ENOSPC:122
1711 This option will ignore EAGAIN from READ, and ENOSPC and
1712 122(EDQUOT) from WRITE.
1714 error_dump=bool If set dump every error even if it is non fatal, true
1715 by default. If disabled only fatal error will be dumped
1717 cgroup=str Add job to this control group. If it doesn't exist, it will
1718 be created. The system must have a mounted cgroup blkio
1719 mount point for this to work. If your system doesn't have it
1720 mounted, you can do so with:
1722 # mount -t cgroup -o blkio none /cgroup
1724 cgroup_weight=int Set the weight of the cgroup to this value. See
1725 the documentation that comes with the kernel, allowed values
1726 are in the range of 100..1000.
1728 cgroup_nodelete=bool Normally fio will delete the cgroups it has created after
1729 the job completion. To override this behavior and to leave
1730 cgroups around after the job completion, set cgroup_nodelete=1.
1731 This can be useful if one wants to inspect various cgroup
1732 files after job completion. Default: false
1734 uid=int Instead of running as the invoking user, set the user ID to
1735 this value before the thread/process does any work.
1737 gid=int Set group ID, see uid.
1739 flow_id=int The ID of the flow. If not specified, it defaults to being a
1740 global flow. See flow.
1742 flow=int Weight in token-based flow control. If this value is used, then
1743 there is a 'flow counter' which is used to regulate the
1744 proportion of activity between two or more jobs. fio attempts
1745 to keep this flow counter near zero. The 'flow' parameter
1746 stands for how much should be added or subtracted to the flow
1747 counter on each iteration of the main I/O loop. That is, if
1748 one job has flow=8 and another job has flow=-1, then there
1749 will be a roughly 1:8 ratio in how much one runs vs the other.
1751 flow_watermark=int The maximum value that the absolute value of the flow
1752 counter is allowed to reach before the job must wait for a
1753 lower value of the counter.
1755 flow_sleep=int The period of time, in microseconds, to wait after the flow
1756 watermark has been exceeded before retrying operations
1758 In addition, there are some parameters which are only valid when a specific
1759 ioengine is in use. These are used identically to normal parameters, with the
1760 caveat that when used on the command line, they must come after the ioengine
1761 that defines them is selected.
1763 [libaio] userspace_reap Normally, with the libaio engine in use, fio will use
1764 the io_getevents system call to reap newly returned events.
1765 With this flag turned on, the AIO ring will be read directly
1766 from user-space to reap events. The reaping mode is only
1767 enabled when polling for a minimum of 0 events (eg when
1768 iodepth_batch_complete=0).
1770 [cpu] cpuload=int Attempt to use the specified percentage of CPU cycles.
1772 [cpu] cpuchunks=int Split the load into cycles of the given time. In
1775 [cpu] exit_on_io_done=bool Detect when IO threads are done, then exit.
1777 [netsplice] hostname=str
1778 [net] hostname=str The host name or IP address to use for TCP or UDP based IO.
1779 If the job is a TCP listener or UDP reader, the hostname is not
1780 used and must be omitted unless it is a valid UDP multicast
1782 [libhdfs] namenode=str The host name or IP address of a HDFS cluster namenode to contact.
1784 [netsplice] port=int
1785 [net] port=int The TCP or UDP port to bind to or connect to. If this is used
1786 with numjobs to spawn multiple instances of the same job type, then this will
1787 be the starting port number since fio will use a range of ports.
1788 [libhdfs] port=int the listening port of the HFDS cluster namenode.
1790 [netsplice] interface=str
1791 [net] interface=str The IP address of the network interface used to send or
1792 receive UDP multicast
1795 [net] ttl=int Time-to-live value for outgoing UDP multicast packets.
1798 [netsplice] nodelay=bool
1799 [net] nodelay=bool Set TCP_NODELAY on TCP connections.
1801 [netsplice] protocol=str
1802 [netsplice] proto=str
1804 [net] proto=str The network protocol to use. Accepted values are:
1806 tcp Transmission control protocol
1807 tcpv6 Transmission control protocol V6
1808 udp User datagram protocol
1809 udpv6 User datagram protocol V6
1810 unix UNIX domain socket
1812 When the protocol is TCP or UDP, the port must also be given,
1813 as well as the hostname if the job is a TCP listener or UDP
1814 reader. For unix sockets, the normal filename option should be
1815 used and the port is invalid.
1817 [net] listen For TCP network connections, tell fio to listen for incoming
1818 connections rather than initiating an outgoing connection. The
1819 hostname must be omitted if this option is used.
1821 [net] pingpong Normaly a network writer will just continue writing data, and
1822 a network reader will just consume packages. If pingpong=1
1823 is set, a writer will send its normal payload to the reader,
1824 then wait for the reader to send the same payload back. This
1825 allows fio to measure network latencies. The submission
1826 and completion latencies then measure local time spent
1827 sending or receiving, and the completion latency measures
1828 how long it took for the other end to receive and send back.
1829 For UDP multicast traffic pingpong=1 should only be set for a
1830 single reader when multiple readers are listening to the same
1833 [net] window_size Set the desired socket buffer size for the connection.
1835 [net] mss Set the TCP maximum segment size (TCP_MAXSEG).
1837 [e4defrag] donorname=str
1838 File will be used as a block donor(swap extents between files)
1839 [e4defrag] inplace=int
1840 Configure donor file blocks allocation strategy
1841 0(default): Preallocate donor's file on init
1842 1 : allocate space immidietly inside defragment event,
1843 and free right after event
1845 [mtd] skip_bad=bool Skip operations against known bad blocks.
1847 [libhdfs] hdfsdirectory libhdfs will create chunk in this HDFS directory
1848 [libhdfs] chunck_size the size of the chunck to use for each file.
1851 6.0 Interpreting the output
1852 ---------------------------
1854 fio spits out a lot of output. While running, fio will display the
1855 status of the jobs created. An example of that would be:
1857 Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s]
1859 The characters inside the square brackets denote the current status of
1860 each thread. The possible values (in typical life cycle order) are:
1864 P Thread setup, but not started.
1866 I Thread initialized, waiting or generating necessary data.
1867 p Thread running pre-reading file(s).
1868 R Running, doing sequential reads.
1869 r Running, doing random reads.
1870 W Running, doing sequential writes.
1871 w Running, doing random writes.
1872 M Running, doing mixed sequential reads/writes.
1873 m Running, doing mixed random reads/writes.
1874 F Running, currently waiting for fsync()
1875 f Running, finishing up (writing IO logs, etc)
1876 V Running, doing verification of written data.
1877 E Thread exited, not reaped by main thread yet.
1879 X Thread reaped, exited with an error.
1880 K Thread reaped, exited due to signal.
1882 Fio will condense the thread string as not to take up more space on the
1883 command line as is needed. For instance, if you have 10 readers and 10
1884 writers running, the output would look like this:
1886 Jobs: 20 (f=20): [R(10),W(10)] [4.0% done] [2103MB/0KB/0KB /s] [538K/0/0 iops] [eta 57m:36s]
1888 Fio will still maintain the ordering, though. So the above means that jobs
1889 1..10 are readers, and 11..20 are writers.
1891 The other values are fairly self explanatory - number of threads
1892 currently running and doing io, rate of io since last check (read speed
1893 listed first, then write speed), and the estimated completion percentage
1894 and time for the running group. It's impossible to estimate runtime of
1895 the following groups (if any). Note that the string is displayed in order,
1896 so it's possible to tell which of the jobs are currently doing what. The
1897 first character is the first job defined in the job file, and so forth.
1899 When fio is done (or interrupted by ctrl-c), it will show the data for
1900 each thread, group of threads, and disks in that order. For each data
1901 direction, the output looks like:
1903 Client1 (g=0): err= 0:
1904 write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec
1905 slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
1906 clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
1907 bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
1908 cpu : usr=1.49%, sys=0.25%, ctx=7969, majf=0, minf=17
1909 IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0%
1910 submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1911 complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
1912 issued r/w: total=0/32768, short=0/0
1913 lat (msec): 2=1.6%, 4=0.0%, 10=3.2%, 20=12.8%, 50=38.4%, 100=24.8%,
1914 lat (msec): 250=15.2%, 500=0.0%, 750=0.0%, 1000=0.0%, >=2048=0.0%
1916 The client number is printed, along with the group id and error of that
1917 thread. Below is the io statistics, here for writes. In the order listed,
1920 io= Number of megabytes io performed
1921 bw= Average bandwidth rate
1922 iops= Average IOs performed per second
1923 runt= The runtime of that thread
1924 slat= Submission latency (avg being the average, stdev being the
1925 standard deviation). This is the time it took to submit
1926 the io. For sync io, the slat is really the completion
1927 latency, since queue/complete is one operation there. This
1928 value can be in milliseconds or microseconds, fio will choose
1929 the most appropriate base and print that. In the example
1930 above, milliseconds is the best scale. Note: in --minimal mode
1931 latencies are always expressed in microseconds.
1932 clat= Completion latency. Same names as slat, this denotes the
1933 time from submission to completion of the io pieces. For
1934 sync io, clat will usually be equal (or very close) to 0,
1935 as the time from submit to complete is basically just
1936 CPU time (io has already been done, see slat explanation).
1937 bw= Bandwidth. Same names as the xlat stats, but also includes
1938 an approximate percentage of total aggregate bandwidth
1939 this thread received in this group. This last value is
1940 only really useful if the threads in this group are on the
1941 same disk, since they are then competing for disk access.
1942 cpu= CPU usage. User and system time, along with the number
1943 of context switches this thread went through, usage of
1944 system and user time, and finally the number of major
1945 and minor page faults.
1946 IO depths= The distribution of io depths over the job life time. The
1947 numbers are divided into powers of 2, so for example the
1948 16= entries includes depths up to that value but higher
1949 than the previous entry. In other words, it covers the
1950 range from 16 to 31.
1951 IO submit= How many pieces of IO were submitting in a single submit
1952 call. Each entry denotes that amount and below, until
1953 the previous entry - eg, 8=100% mean that we submitted
1954 anywhere in between 5-8 ios per submit call.
1955 IO complete= Like the above submit number, but for completions instead.
1956 IO issued= The number of read/write requests issued, and how many
1958 IO latencies= The distribution of IO completion latencies. This is the
1959 time from when IO leaves fio and when it gets completed.
1960 The numbers follow the same pattern as the IO depths,
1961 meaning that 2=1.6% means that 1.6% of the IO completed
1962 within 2 msecs, 20=12.8% means that 12.8% of the IO
1963 took more than 10 msecs, but less than (or equal to) 20 msecs.
1965 After each client has been listed, the group statistics are printed. They
1966 will look like this:
1968 Run status group 0 (all jobs):
1969 READ: io=64MB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec
1970 WRITE: io=64MB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec
1972 For each data direction, it prints:
1974 io= Number of megabytes io performed.
1975 aggrb= Aggregate bandwidth of threads in this group.
1976 minb= The minimum average bandwidth a thread saw.
1977 maxb= The maximum average bandwidth a thread saw.
1978 mint= The smallest runtime of the threads in that group.
1979 maxt= The longest runtime of the threads in that group.
1981 And finally, the disk statistics are printed. They will look like this:
1983 Disk stats (read/write):
1984 sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
1986 Each value is printed for both reads and writes, with reads first. The
1989 ios= Number of ios performed by all groups.
1990 merge= Number of merges io the io scheduler.
1991 ticks= Number of ticks we kept the disk busy.
1992 io_queue= Total time spent in the disk queue.
1993 util= The disk utilization. A value of 100% means we kept the disk
1994 busy constantly, 50% would be a disk idling half of the time.
1996 It is also possible to get fio to dump the current output while it is
1997 running, without terminating the job. To do that, send fio the USR1 signal.
1998 You can also get regularly timed dumps by using the --status-interval
1999 parameter, or by creating a file in /tmp named fio-dump-status. If fio
2000 sees this file, it will unlink it and dump the current output status.
2006 For scripted usage where you typically want to generate tables or graphs
2007 of the results, fio can output the results in a semicolon separated format.
2008 The format is one long line of values, such as:
2010 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%
2011 A description of this job goes here.
2013 The job description (if provided) follows on a second line.
2015 To enable terse output, use the --minimal command line option. The first
2016 value is the version of the terse output format. If the output has to
2017 be changed for some reason, this number will be incremented by 1 to
2018 signify that change.
2020 Split up, the format is as follows:
2022 terse version, fio version, jobname, groupid, error
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
2031 Total IO (KB), bandwidth (KB/sec), IOPS, runtime (msec)
2032 Submission latency: min, max, mean, stdev (usec)
2033 Completion latency: min, max, mean, stdev(usec)
2034 Completion latency percentiles: 20 fields (see below)
2035 Total latency: min, max, mean, stdev (usec)
2036 Bw (KB/s): min, max, aggregate percentage of total, mean, stdev
2037 CPU usage: user, system, context switches, major faults, minor faults
2038 IO depths: <=1, 2, 4, 8, 16, 32, >=64
2039 IO latencies microseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
2040 IO latencies milliseconds: <=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
2041 Disk utilization: Disk name, Read ios, write ios,
2042 Read merges, write merges,
2043 Read ticks, write ticks,
2044 Time spent in queue, disk utilization percentage
2045 Additional Info (dependent on continue_on_error, default off): total # errors, first error code
2047 Additional Info (dependent on description being set): Text description
2049 Completion latency percentiles can be a grouping of up to 20 sets, so
2050 for the terse output fio writes all of them. Each field will look like this:
2054 which is the Xth percentile, and the usec latency associated with it.
2056 For disk utilization, all disks used by fio are shown. So for each disk
2057 there will be a disk utilization section.
2060 8.0 Trace file format
2061 ---------------------
2062 There are two trace file format that you can encounter. The older (v1) format
2063 is unsupported since version 1.20-rc3 (March 2008). It will still be described
2064 below in case that you get an old trace and want to understand it.
2066 In any case the trace is a simple text file with a single action per line.
2069 8.1 Trace file format v1
2070 ------------------------
2071 Each line represents a single io action in the following format:
2075 where rw=0/1 for read/write, and the offset and length entries being in bytes.
2077 This format is not supported in Fio versions => 1.20-rc3.
2080 8.2 Trace file format v2
2081 ------------------------
2082 The second version of the trace file format was added in Fio version 1.17.
2083 It allows to access more then one file per trace and has a bigger set of
2084 possible file actions.
2086 The first line of the trace file has to be:
2090 Following this can be lines in two different formats, which are described below.
2092 The file management format:
2096 The filename is given as an absolute path. The action can be one of these:
2098 add Add the given filename to the trace
2099 open Open the file with the given filename. The filename has to have
2100 been added with the add action before.
2101 close Close the file with the given filename. The file has to have been
2105 The file io action format:
2107 filename action offset length
2109 The filename is given as an absolute path, and has to have been added and opened
2110 before it can be used with this format. The offset and length are given in
2111 bytes. The action can be one of these:
2113 wait Wait for 'offset' microseconds. Everything below 100 is discarded.
2114 The time is relative to the previous wait statement.
2115 read Read 'length' bytes beginning from 'offset'
2116 write Write 'length' bytes beginning from 'offset'
2117 sync fsync() the file
2118 datasync fdatasync() the file
2119 trim trim the given file from the given 'offset' for 'length' bytes
2122 9.0 CPU idleness profiling
2123 --------------------------
2124 In some cases, we want to understand CPU overhead in a test. For example,
2125 we test patches for the specific goodness of whether they reduce CPU usage.
2126 fio implements a balloon approach to create a thread per CPU that runs at
2127 idle priority, meaning that it only runs when nobody else needs the cpu.
2128 By measuring the amount of work completed by the thread, idleness of each
2129 CPU can be derived accordingly.
2131 An unit work is defined as touching a full page of unsigned characters. Mean
2132 and standard deviation of time to complete an unit work is reported in "unit
2133 work" section. Options can be chosen to report detailed percpu idleness or
2134 overall system idleness by aggregating percpu stats.
2137 10.0 Verification and triggers
2138 ------------------------------
2139 Fio is usually run in one of two ways, when data verification is done. The
2140 first is a normal write job of some sort with verify enabled. When the
2141 write phase has completed, fio switches to reads and verifies everything
2142 it wrote. The second model is running just the write phase, and then later
2143 on running the same job (but with reads instead of writes) to repeat the
2144 same IO patterns and verify the contents. Both of these methods depend
2145 on the write phase being completed, as fio otherwise has no idea how much
2148 With verification triggers, fio supports dumping the current write state
2149 to local files. Then a subsequent read verify workload can load this state
2150 and know exactly where to stop. This is useful for testing cases where
2151 power is cut to a server in a managed fashion, for instance.
2153 A verification trigger consists of two things:
2155 1) Storing the write state of each job
2156 2) Executing a trigger command
2158 The write state is relatively small, on the order of hundreds of bytes
2159 to single kilobytes. It contains information on the number of completions
2160 done, the last X completions, etc.
2162 A trigger is invoked either through creation ('touch') of a specified
2163 file in the system, or through a timeout setting. If fio is run with
2164 --trigger-file=/tmp/trigger-file, then it will continually check for
2165 the existence of /tmp/trigger-file. When it sees this file, it will
2166 fire off the trigger (thus saving state, and executing the trigger
2169 For client/server runs, there's both a local and remote trigger. If
2170 fio is running as a server backend, it will send the job states back
2171 to the client for safe storage, then execute the remote trigger, if
2172 specified. If a local trigger is specified, the server will still send
2173 back the write state, but the client will then execute the trigger.
2175 10.1 Verification trigger example
2176 ---------------------------------
2177 Lets say we want to run a powercut test on the remote machine 'server'.
2178 Our write workload is in write-test.fio. We want to cut power to 'server'
2179 at some point during the run, and we'll run this test from the safety
2180 or our local machine, 'localbox'. On the server, we'll start the fio
2183 server# fio --server
2185 and on the client, we'll fire off the workload:
2187 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger-remote="bash -c \"echo b > /proc/sysrq-triger\""
2189 We set /tmp/my-trigger as the trigger file, and we tell fio to execute
2191 echo b > /proc/sysrq-trigger
2193 on the server once it has received the trigger and sent us the write
2194 state. This will work, but it's not _really_ cutting power to the server,
2195 it's merely abruptly rebooting it. If we have a remote way of cutting
2196 power to the server through IPMI or similar, we could do that through
2197 a local trigger command instead. Lets assume we have a script that does
2198 IPMI reboot of a given hostname, ipmi-reboot. On localbox, we could
2199 then have run fio with a local trigger instead:
2201 localbox$ fio --client=server --trigger-file=/tmp/my-trigger --trigger="ipmi-reboot server"
2203 For this case, fio would wait for the server to send us the write state,
2204 then execute 'ipmi-reboot server' when that happened.
2206 10.1 Loading verify state
2207 -------------------------
2208 To load store write state, read verification job file must contain
2209 the verify_state_load option. If that is set, fio will load the previously
2210 stored state. For a local fio run this is done by loading the files directly,
2211 and on a client/server run, the server backend will ask the client to send
2212 the files over and load them from there.