Provided by: fio_3.30-1_amd64 
NAME
fio - flexible I/O tester
SYNOPSIS
fio [options] [jobfile]...
DESCRIPTION
fio is a tool that will spawn a number of threads or processes doing a particular type of
I/O action as specified by the user. The typical use of fio is to write a job file
matching the I/O load one wants to simulate.
OPTIONS
--debug=type
Enable verbose tracing type of various fio actions. May be `all' for all types or
individual types separated by a comma (e.g. `--debug=file,mem' will enable file and
memory debugging). `help' will list all available tracing options.
--parse-only
Parse options only, don't start any I/O.
--merge-blktrace-only
Merge blktraces only, don't start any I/O.
--output=filename
Write output to filename.
--output-format=format
Set the reporting format to `normal', `terse', `json', or `json+'. Multiple formats
can be selected, separate by a comma. `terse' is a CSV based format. `json+' is
like `json', except it adds a full dump of the latency buckets.
--bandwidth-log
Generate aggregate bandwidth logs.
--minimal
Print statistics in a terse, semicolon-delimited format.
--append-terse
Print statistics in selected mode AND terse, semicolon-delimited format.
Deprecated, use --output-format instead to select multiple formats.
--terse-version=version
Set terse version output format (default `3', or `2', `4', `5').
--version
Print version information and exit.
--help Print a summary of the command line options and exit.
--cpuclock-test
Perform test and validation of internal CPU clock.
--crctest=[test]
Test the speed of the built-in checksumming functions. If no argument is given, all
of them are tested. Alternatively, a comma separated list can be passed, in which
case the given ones are tested.
--cmdhelp=command
Print help information for command. May be `all' for all commands.
--enghelp=[ioengine[,command]]
List all commands defined by ioengine, or print help for command defined by
ioengine. If no ioengine is given, list all available ioengines.
--showcmd=jobfile
Convert jobfile to a set of command-line options.
--readonly
Turn on safety read-only checks, preventing writes and trims. The --readonly option
is an extra safety guard to prevent users from accidentally starting a write or
trim workload when that is not desired. Fio will only modify the device under test
if `rw=write/randwrite/rw/randrw/trim/randtrim/trimwrite' is given. This safety net
can be used as an extra precaution.
--eta=when
Specifies when real-time ETA estimate should be printed. when may be `always',
`never' or `auto'. `auto' is the default, it prints ETA when requested if the
output is a TTY. `always' disregards the output type, and prints ETA when
requested. `never' never prints ETA.
--eta-interval=time
By default, fio requests client ETA status roughly every second. With this option,
the interval is configurable. Fio imposes a minimum allowed time to avoid flooding
the console, less than 250 msec is not supported.
--eta-newline=time
Force a new line for every time period passed. When the unit is omitted, the value
is interpreted in seconds.
--status-interval=time
Force a full status dump of cumulative (from job start) values at time intervals.
This option does *not* provide per-period measurements. So values such as bandwidth
are running averages. When the time unit is omitted, time is interpreted in
seconds. Note that using this option with `--output-format=json' will yield output
that technically isn't valid json, since the output will be collated sets of valid
json. It will need to be split into valid sets of json after the run.
--section=name
Only run specified section name in job file. Multiple sections can be specified.
The --section option allows one to combine related jobs into one file. E.g. one
job file could define light, moderate, and heavy sections. Tell fio to run only the
"heavy" section by giving `--section=heavy' command line option. One can also
specify the "write" operations in one section and "verify" operation in another
section. The --section option only applies to job sections. The reserved *global*
section is always parsed and used.
--alloc-size=kb
Allocate additional internal smalloc pools of size kb in KiB. The --alloc-size
option increases shared memory set aside for use by fio. If running large jobs
with randommap enabled, fio can run out of memory. Smalloc is an internal
allocator for shared structures from a fixed size memory pool and can grow to 16
pools. The pool size defaults to 16MiB. NOTE: While running `.fio_smalloc.*'
backing store files are visible in `/tmp'.
--warnings-fatal
All fio parser warnings are fatal, causing fio to exit with an error.
--max-jobs=nr
Set the maximum number of threads/processes to support to nr. NOTE: On Linux, it
may be necessary to increase the shared-memory limit (`/proc/sys/kernel/shmmax') if
fio runs into errors while creating jobs.
--server=args
Start a backend server, with args specifying what to listen to. See CLIENT/SERVER
section.
--daemonize=pidfile
Background a fio server, writing the pid to the given pidfile file.
--client=hostname
Instead of running the jobs locally, send and run them on the given hostname or set
of hostnames. See CLIENT/SERVER section.
--remote-config=file
Tell fio server to load this local file.
--idle-prof=option
Report CPU idleness. option is one of the following:
calibrate
Run unit work calibration only and exit.
system Show aggregate system idleness and unit work.
percpu As system but also show per CPU idleness.
--inflate-log=log
Inflate and output compressed log.
--trigger-file=file
Execute trigger command when file exists.
--trigger-timeout=time
Execute trigger at this time.
--trigger=command
Set this command as local trigger.
--trigger-remote=command
Set this command as remote trigger.
--aux-path=path
Use the directory specified by path for generated state files instead of the
current working directory.
JOB FILE FORMAT
Any parameters following the options will be assumed to be job files, unless they match a
job file parameter. Multiple job files can be listed and each job file will be regarded as
a separate group. Fio will stonewall execution between each group.
Fio accepts one or more job files describing what it is supposed to do. The job file
format is the classic ini file, where the names enclosed in [] brackets define the job
name. You are free to use any ASCII name you want, except *global* which has special
meaning. Following the job name is a sequence of zero or more parameters, one per line,
that define the behavior of the job. If the first character in a line is a ';' or a '#',
the entire line is discarded as a comment.
A *global* section sets defaults for the jobs described in that file. A job may override a
*global* section parameter, and a job file may even have several *global* sections if so
desired. A job is only affected by a *global* section residing above it.
The --cmdhelp option also lists all options. If used with an command argument, --cmdhelp
will detail the given command.
See the `examples/' directory for inspiration on how to write job files. Note the
copyright and license requirements currently apply to `examples/' files.
Note that the maximum length of a line in the job file is 8192 bytes.
JOB FILE PARAMETERS
Some parameters take an option of a given type, such as an integer or a string. Anywhere a
numeric value is required, an arithmetic expression may be used, provided it is surrounded
by parentheses. Supported operators are:
addition (+)
subtraction (-)
multiplication (*)
division (/)
modulus (%)
exponentiation (^)
For time values in expressions, units are microseconds by default. This is different than
for time values not in expressions (not enclosed in parentheses).
PARAMETER TYPES
The following parameter types are used.
str String. A sequence of alphanumeric characters.
time Integer with possible time suffix. Without a unit value is interpreted as seconds
unless otherwise specified. Accepts a suffix of 'd' for days, 'h' for hours, 'm'
for minutes, 's' for seconds, 'ms' (or 'msec') for milliseconds and 'us' (or
'usec') for microseconds. For example, use 10m for 10 minutes.
int Integer. A whole number value, which may contain an integer prefix and an integer
suffix.
[*integer prefix*] **number** [*integer suffix*]
The optional *integer prefix* specifies the number's base. The default is decimal.
*0x* specifies hexadecimal.
The optional *integer suffix* specifies the number's units, and includes an
optional unit prefix and an optional unit. For quantities of data, the default unit
is bytes. For quantities of time, the default unit is seconds unless otherwise
specified.
With `kb_base=1000', fio follows international standards for unit prefixes. To
specify power-of-10 decimal values defined in the International System of Units
(SI):
K means kilo (K) or 1000
M means mega (M) or 1000**2
G means giga (G) or 1000**3
T means tera (T) or 1000**4
P means peta (P) or 1000**5
To specify power-of-2 binary values defined in IEC 80000-13:
Ki means kibi (Ki) or 1024
Mi means mebi (Mi) or 1024**2
Gi means gibi (Gi) or 1024**3
Ti means tebi (Ti) or 1024**4
Pi means pebi (Pi) or 1024**5
For Zone Block Device Mode:
z means Zone
With `kb_base=1024' (the default), the unit prefixes are opposite from those
specified in the SI and IEC 80000-13 standards to provide compatibility with old
scripts. For example, 4k means 4096.
For quantities of data, an optional unit of 'B' may be included (e.g., 'kB' is the
same as 'k').
The *integer suffix* is not case sensitive (e.g., m/mi mean mebi/mega, not milli).
'b' and 'B' both mean byte, not bit.
Examples with `kb_base=1000':
4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
1 MiB: 1048576, 1m, 1024k
1 MB: 1000000, 1mi, 1000ki
1 TiB: 1073741824, 1t, 1024m, 1048576k
1 TB: 1000000000, 1ti, 1000mi, 1000000ki
Examples with `kb_base=1024' (default):
4 KiB: 4096, 4096b, 4096B, 4k, 4kb, 4kB, 4K, 4KB
1 MiB: 1048576, 1m, 1024k
1 MB: 1000000, 1mi, 1000ki
1 TiB: 1073741824, 1t, 1024m, 1048576k
1 TB: 1000000000, 1ti, 1000mi, 1000000ki
To specify times (units are not case sensitive):
D means days
H means hours
M mean minutes
s or sec means seconds (default)
ms or msec means milliseconds
us or usec means microseconds
`z' suffix specifies that the value is measured in zones. Value is recalculated
once block device's zone size becomes known.
If the option accepts an upper and lower range, use a colon ':' or minus '-' to
separate such values. See irange parameter type. If the lower value specified
happens to be larger than the upper value the two values are swapped.
bool Boolean. Usually parsed as an integer, however only defined for true and false (1
and 0).
irange Integer range with suffix. Allows value range to be given, such as 1024-4096. A
colon may also be used as the separator, e.g. 1k:4k. If the option allows two sets
of ranges, they can be specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also
see int parameter type.
float_list
A list of floating point numbers, separated by a ':' character.
JOB PARAMETERS
With the above in mind, here follows the complete list of fio job parameters.
Units
kb_base=int
Select the interpretation of unit prefixes in input parameters.
1000 Inputs comply with IEC 80000-13 and the International System of Units
(SI). Use:
- power-of-2 values with IEC prefixes (e.g., KiB)
- power-of-10 values with SI prefixes (e.g., kB)
1024 Compatibility mode (default). To avoid breaking old scripts:
- power-of-2 values with SI prefixes
- power-of-10 values with IEC prefixes
See bs for more details on input parameters.
Outputs always use correct prefixes. Most outputs include both side-by-side, like:
bw=2383.3kB/s (2327.4KiB/s)
If only one value is reported, then kb_base selects the one to use:
1000 -- SI prefixes
1024 -- IEC prefixes
unit_base=int
Base unit for reporting. Allowed values are:
0 Use auto-detection (default).
8 Byte based.
1 Bit based.
Job description
name=str
ASCII name of the job. This may be used to override the name printed by fio for
this job. Otherwise the job name is used. On the command line this parameter has
the special purpose of also signaling the start of a new job.
description=str
Text description of the job. Doesn't do anything except dump this text description
when this job is run. It's not parsed.
loops=int
Run the specified number of iterations of this job. Used to repeat the same
workload a given number of times. Defaults to 1.
numjobs=int
Create the specified number of clones of this job. Each clone of job is spawned as
an independent thread or process. May be used to setup a larger number of
threads/processes doing the same thing. Each thread is reported separately; to see
statistics for all clones as a whole, use group_reporting in conjunction with
new_group. See --max-jobs. Default: 1.
Time related parameters
runtime=time
Tell fio to terminate processing after the specified period of time. It can be
quite hard to determine for how long a specified job will run, so this parameter is
handy to cap the total runtime to a given time. When the unit is omitted, the value
is interpreted in seconds.
time_based
If set, fio will run for the duration of the runtime specified even if the file(s)
are completely read or written. It will simply loop over the same workload as many
times as the runtime allows.
startdelay=irange(int)
Delay the start of job for the specified amount of time. Can be a single value or a
range. When given as a range, each thread will choose a value randomly from within
the range. Value is in seconds if a unit is omitted.
ramp_time=time
If set, fio will run the specified workload for this amount of time before logging
any performance numbers. Useful for letting performance settle before logging
results, thus minimizing the runtime required for stable results. Note that the
ramp_time is considered lead in time for a job, thus it will increase the total
runtime if a special timeout or runtime is specified. When the unit is omitted, the
value is given in seconds.
clocksource=str
Use the given clocksource as the base of timing. The supported options are:
gettimeofday
gettimeofday(2)
clock_gettime
clock_gettime(2)
cpu Internal CPU clock source
cpu is the preferred clocksource if it is reliable, as it is very fast (and fio is
heavy on time calls). Fio will automatically use this clocksource if it's supported
and considered reliable on the system it is running on, unless another clocksource
is specifically set. For x86/x86-64 CPUs, this means supporting TSC Invariant.
gtod_reduce=bool
Enable all of the gettimeofday(2) reducing options (disable_clat, disable_slat,
disable_bw_measurement) plus reduce precision of the timeout somewhat to really
shrink the gettimeofday(2) call count. With this option enabled, we only do about
0.4% of the gettimeofday(2) calls we would have done if all time keeping was
enabled.
gtod_cpu=int
Sometimes it's cheaper to dedicate a single thread of execution to just getting the
current time. Fio (and databases, for instance) are very intensive on
gettimeofday(2) calls. With this option, you can set one CPU aside for doing
nothing but logging current time to a shared memory location. Then the other
threads/processes that run I/O workloads need only copy that segment, instead of
entering the kernel with a gettimeofday(2) call. The CPU set aside for doing these
time calls will be excluded from other uses. Fio will manually clear it from the
CPU mask of other jobs.
Target file/device
directory=str
Prefix filenames with this directory. Used to place files in a different location
than `./'. You can specify a number of directories by separating the names with a
':' character. These directories will be assigned equally distributed to job clones
created by numjobs as long as they are using generated filenames. If specific
filename(s) are set fio will use the first listed directory, and thereby matching
the filename semantic (which generates a file for each clone if not specified, but
lets all clones use the same file if set).
See the filename option for information on how to escape ':' characters within the
directory path itself.
Note: To control the directory fio will use for internal state files use
--aux-path.
filename=str
Fio normally makes up a filename based on the job name, thread number, and file
number (see filename_format). If you want to share files between threads in a job
or several jobs with fixed file paths, specify a filename for each of them to
override the default. If the ioengine is file based, you can specify a number of
files by separating the names with a ':' colon. So if you wanted a job to open
`/dev/sda' and `/dev/sdb' as the two working files, you would use
`filename=/dev/sda:/dev/sdb'. This also means that whenever this option is
specified, nrfiles is ignored. The size of regular files specified by this option
will be size divided by number of files unless an explicit size is specified by
filesize.
Each colon in the wanted path must be escaped with a '\' character. For instance,
if the path is `/dev/dsk/foo@3,0:c' then you would use
`filename=/dev/dsk/foo@3,0\:c' and if the path is `F:\filename' then you would use
`filename=F\:\filename'.
On Windows, disk devices are accessed as `\\.\PhysicalDrive0' for the first device,
`\\.\PhysicalDrive1' for the second etc. Note: Windows and FreeBSD prevent write
access to areas of the disk containing in-use data (e.g. filesystems).
The filename `-' is a reserved name, meaning *stdin* or *stdout*. Which of the two
depends on the read/write direction set.
filename_format=str
If sharing multiple files between jobs, it is usually necessary to have fio
generate the exact names that you want. By default, fio will name a file based on
the default file format specification of `jobname.jobnumber.filenumber'. With this
option, that can be customized. Fio will recognize and replace the following
keywords in this string:
$jobname
The name of the worker thread or process.
$clientuid
IP of the fio process when using client/server mode.
$jobnum
The incremental number of the worker thread or process.
$filenum
The incremental number of the file for that worker thread or process.
To have dependent jobs share a set of files, this option can be set to have fio
generate filenames that are shared between the two. For instance, if
`testfiles.$filenum' is specified, file number 4 for any job will be named
`testfiles.4'. The default of `$jobname.$jobnum.$filenum' will be used if no other
format specifier is given.
If you specify a path then the directories will be created up to the main directory
for the file. So for example if you specify `a/b/c/$jobnum` then the directories
a/b/c will be created before the file setup part of the job. If you specify
directory then the path will be relative that directory, otherwise it is treated as
the absolute path.
unique_filename=bool
To avoid collisions between networked clients, fio defaults to prefixing any
generated filenames (with a directory specified) with the source of the client
connecting. To disable this behavior, set this option to 0.
opendir=str
Recursively open any files below directory str.
lockfile=str
Fio defaults to not locking any files before it does I/O to them. If a file or file
descriptor is shared, fio can serialize I/O to that file to make the end result
consistent. This is usual for emulating real workloads that share files. The lock
modes are:
none No locking. The default.
exclusive
Only one thread or process may do I/O at a time, excluding all
others.
readwrite
Read-write locking on the file. Many readers may access the file at
the same time, but writes get exclusive access.
nrfiles=int
Number of files to use for this job. Defaults to 1. The size of files will be size
divided by this unless explicit size is specified by filesize. Files are created
for each thread separately, and each file will have a file number within its name
by default, as explained in filename section.
openfiles=int
Number of files to keep open at the same time. Defaults to the same as nrfiles, can
be set smaller to limit the number simultaneous opens.
file_service_type=str
Defines how fio decides which file from a job to service next. The following types
are defined:
random Choose a file at random.
roundrobin
Round robin over opened files. This is the default.
sequential
Finish one file before moving on to the next. Multiple files can
still be open depending on openfiles.
zipf Use a Zipf distribution to decide what file to access.
pareto Use a Pareto distribution to decide what file to access.
normal Use a Gaussian (normal) distribution to decide what file to access.
gauss Alias for normal.
For random, roundrobin, and sequential, a postfix can be appended to tell fio how
many I/Os to issue before switching to a new file. For example, specifying
`file_service_type=random:8' would cause fio to issue 8 I/Os before selecting a new
file at random. For the non-uniform distributions, a floating point postfix can be
given to influence how the distribution is skewed. See random_distribution for a
description of how that would work.
ioscheduler=str
Attempt to switch the device hosting the file to the specified I/O scheduler before
running. If the file is a pipe, a character device file or if device hosting the
file could not be determined, this option is ignored.
create_serialize=bool
If true, serialize the file creation for the jobs. This may be handy to avoid
interleaving of data files, which may greatly depend on the filesystem used and
even the number of processors in the system. Default: true.
create_fsync=bool
fsync(2) the data file after creation. This is the default.
create_on_open=bool
If true, don't pre-create files but allow the job's open() to create a file when
it's time to do I/O. Default: false -- pre-create all necessary files when the job
starts.
create_only=bool
If true, fio will only run the setup phase of the job. If files need to be laid out
or updated on disk, only that will be done -- the actual job contents are not
executed. Default: false.
allow_file_create=bool
If true, fio is permitted to create files as part of its workload. If this option
is false, then fio will error out if the files it needs to use don't already exist.
Default: true.
allow_mounted_write=bool
If this isn't set, fio will abort jobs that are destructive (e.g. that write) to
what appears to be a mounted device or partition. This should help catch creating
inadvertently destructive tests, not realizing that the test will destroy data on
the mounted file system. Note that some platforms don't allow writing against a
mounted device regardless of this option. Default: false.
pre_read=bool
If this is given, files will be pre-read into memory before starting the given I/O
operation. This will also clear the invalidate flag, since it is pointless to pre-
read and then drop the cache. This will only work for I/O engines that are seek-
able, since they allow you to read the same data multiple times. Thus it will not
work on non-seekable I/O engines (e.g. network, splice). Default: false.
unlink=bool
Unlink the job files when done. Not the default, as repeated runs of that job would
then waste time recreating the file set again and again. Default: false.
unlink_each_loop=bool
Unlink job files after each iteration or loop. Default: false.
zonemode=str
Accepted values are:
none The zonerange, zonesize zonecapacity and zoneskip parameters are
ignored.
strided
I/O happens in a single zone until zonesize bytes have been
transferred. After that number of bytes has been transferred
processing of the next zone starts. The zonecapacity parameter is
ignored.
zbd Zoned block device mode. I/O happens sequentially in each zone, even
if random I/O has been selected. Random I/O happens across all zones
instead of being restricted to a single zone. Trim is handled using
a zone reset operation. Trim only considers non-empty sequential
write required and sequential write preferred zones.
zonerange=int
For zonemode=strided, this is the size of a single zone. See also zonesize and
zoneskip.
For zonemode=zbd, this parameter is ignored.
zonesize=int
For zonemode=strided, this is the number of bytes to transfer before skipping
zoneskip bytes. If this parameter is smaller than zonerange then only a fraction of
each zone with zonerange bytes will be accessed. If this parameter is larger than
zonerange then each zone will be accessed multiple times before skipping to the
next zone.
For zonemode=zbd, this is the size of a single zone. The zonerange parameter is
ignored in this mode. For a job accessing a zoned block device, the specified
zonesize must be 0 or equal to the device zone size. For a regular block device or
file, the specified zonesize must be at least 512B.
zonecapacity=int
For zonemode=zbd, this defines the capacity of a single zone, which is the
accessible area starting from the zone start address. This parameter only applies
when using zonemode=zbd in combination with regular block devices. If not
specified it defaults to the zone size. If the target device is a zoned block
device, the zone capacity is obtained from the device information and this option
is ignored.
zoneskip=int[z]
For zonemode=strided, the number of bytes to skip after zonesize bytes of data have
been transferred.
For zonemode=zbd, the zonesize aligned number of bytes to skip once a zone is fully
written (write workloads) or all written data in the zone have been read (read
workloads). This parameter is valid only for sequential workloads and ignored for
random workloads. For read workloads, see also read_beyond_wp.
read_beyond_wp=bool
This parameter applies to zonemode=zbd only.
Zoned block devices are block devices that consist of multiple zones. Each zone has
a type, e.g. conventional or sequential. A conventional zone can be written at any
offset that is a multiple of the block size. Sequential zones must be written
sequentially. The position at which a write must occur is called the write pointer.
A zoned block device can be either host managed or host aware. For host managed
devices the host must ensure that writes happen sequentially. Fio recognizes host
managed devices and serializes writes to sequential zones for these devices.
If a read occurs in a sequential zone beyond the write pointer then the zoned block
device will complete the read without reading any data from the storage medium.
Since such reads lead to unrealistically high bandwidth and IOPS numbers fio only
reads beyond the write pointer if explicitly told to do so. Default: false.
max_open_zones=int
When running a random write test across an entire drive many more zones will be
open than in a typical application workload. Hence this command line option that
allows to limit the number of open zones. The number of open zones is defined as
the number of zones to which write commands are issued by all threads/processes.
job_max_open_zones=int
Limit on the number of simultaneously opened zones per single thread/process.
ignore_zone_limits=bool
If this option is used, fio will ignore the maximum number of open zones limit of
the zoned block device in use, thus allowing the option max_open_zones value to be
larger than the device reported limit. Default: false.
zone_reset_threshold=float
A number between zero and one that indicates the ratio of logical blocks with data
to the total number of logical blocks in the test above which zones should be reset
periodically.
zone_reset_frequency=float
A number between zero and one that indicates how often a zone reset should be
issued if the zone reset threshold has been exceeded. A zone reset is submitted
after each (1 / zone_reset_frequency) write requests. This and the previous
parameter can be used to simulate garbage collection activity.
I/O type
direct=bool
If value is true, use non-buffered I/O. This is usually O_DIRECT. Note that OpenBSD
and ZFS on Solaris don't support direct I/O. On Windows the synchronous ioengines
don't support direct I/O. Default: false.
atomic=bool
If value is true, attempt to use atomic direct I/O. Atomic writes are guaranteed to
be stable once acknowledged by the operating system. Only Linux supports O_ATOMIC
right now.
buffered=bool
If value is true, use buffered I/O. This is the opposite of the direct option.
Defaults to true.
readwrite=str, rw=str
Type of I/O pattern. Accepted values are:
read Sequential reads.
write Sequential writes.
trim Sequential trims (Linux block devices and SCSI character devices
only).
randread
Random reads.
randwrite
Random writes.
randtrim
Random trims (Linux block devices and SCSI character devices only).
rw,readwrite
Sequential mixed reads and writes.
randrw Random mixed reads and writes.
trimwrite
Sequential trim+write sequences. Blocks will be trimmed first, then
the same blocks will be written to.
Fio defaults to read if the option is not specified. For the mixed I/O types, the
default is to split them 50/50. For certain types of I/O the result may still be
skewed a bit, since the speed may be different.
It is possible to specify the number of I/Os to do before getting a new offset by
appending `:<nr>' to the end of the string given. For a random read, it would look
like `rw=randread:8' for passing in an offset modifier with a value of 8. If the
suffix is used with a sequential I/O pattern, then the `<nr>' value specified will
be added to the generated offset for each I/O turning sequential I/O into
sequential I/O with holes. For instance, using `rw=write:4k' will skip 4k for
every write. Also see the rw_sequencer option.
rw_sequencer=str
If an offset modifier is given by appending a number to the `rw=str' line, then
this option controls how that number modifies the I/O offset being generated.
Accepted values are:
sequential
Generate sequential offset.
identical
Generate the same offset.
sequential is only useful for random I/O, where fio would normally generate a new
random offset for every I/O. If you append e.g. 8 to randread, you would get a new
random offset for every 8 I/Os. The result would be a seek for only every 8 I/Os,
instead of for every I/O. Use `rw=randread:8' to specify that. As sequential I/O is
already sequential, setting sequential for that would not result in any
differences. identical behaves in a similar fashion, except it sends the same
offset 8 number of times before generating a new offset.
unified_rw_reporting=str
Fio normally reports statistics on a per data direction basis, meaning that reads,
writes, and trims are accounted and reported separately. This option determines
whether fio reports the results normally, summed together, or as both options.
Accepted values are:
none Normal statistics reporting.
mixed Statistics are summed per data direction and reported together.
both Statistics are reported normally, followed by the mixed statistics.
0 Backward-compatible alias for none.
1 Backward-compatible alias for mixed.
2 Alias for both.
randrepeat=bool
Seed the random number generator used for random I/O patterns in a predictable way
so the pattern is repeatable across runs. Default: true.
allrandrepeat=bool
Seed all random number generators in a predictable way so results are repeatable
across runs. Default: false.
randseed=int
Seed the random number generators based on this seed value, to be able to control
what sequence of output is being generated. If not set, the random sequence depends
on the randrepeat setting.
fallocate=str
Whether pre-allocation is performed when laying down files. Accepted values are:
none Do not pre-allocate space.
native Use a platform's native pre-allocation call but fall back to none
behavior if it fails/is not implemented.
posix Pre-allocate via posix_fallocate(3).
keep Pre-allocate via fallocate(2) with FALLOC_FL_KEEP_SIZE set.
truncate
Extend file to final size using ftruncate|(2) instead of allocating.
0 Backward-compatible alias for none.
1 Backward-compatible alias for posix.
May not be available on all supported platforms. keep is only available on Linux.
If using ZFS on Solaris this cannot be set to posix because ZFS doesn't support
pre-allocation. Default: native if any pre-allocation methods except truncate are
available, none if not.
Note that using truncate on Windows will interact surprisingly with non-sequential
write patterns. When writing to a file that has been extended by setting the end-
of-file information, Windows will backfill the unwritten portion of the file up to
that offset with zeroes before issuing the new write. This means that a single
small write to the end of an extended file will stall until the entire file has
been filled with zeroes.
fadvise_hint=str
Use posix_fadvise(2) or posix_madvise(2) to advise the kernel what I/O patterns are
likely to be issued. Accepted values are:
0 Backwards compatible hint for "no hint".
1 Backwards compatible hint for "advise with fio workload type". This
uses FADV_RANDOM for a random workload, and FADV_SEQUENTIAL for a
sequential workload.
sequential
Advise using FADV_SEQUENTIAL.
random Advise using FADV_RANDOM.
write_hint=str
Use fcntl(2) to advise the kernel what life time to expect from a write. Only
supported on Linux, as of version 4.13. Accepted values are:
none No particular life time associated with this file.
short Data written to this file has a short life time.
medium Data written to this file has a medium life time.
long Data written to this file has a long life time.
extreme
Data written to this file has a very long life time.
The values are all relative to each other, and no absolute meaning should be
associated with them.
offset=int[%|z]
Start I/O at the provided offset in the file, given as either a fixed size in
bytes, zones or a percentage. If a percentage is given, the generated offset will
be aligned to the minimum blocksize or to the value of offset_align if provided.
Data before the given offset will not be touched. This effectively caps the file
size at `real_size - offset'. Can be combined with size to constrain the start and
end range of the I/O workload. A percentage can be specified by a number between 1
and 100 followed by '%', for example, `offset=20%' to specify 20%. In ZBD mode,
value can be set as number of zones using 'z'.
offset_align=int
If set to non-zero value, the byte offset generated by a percentage offset is
aligned upwards to this value. Defaults to 0 meaning that a percentage offset is
aligned to the minimum block size.
offset_increment=int[%|z]
If this is provided, then the real offset becomes `offset + offset_increment *
thread_number', where the thread number is a counter that starts at 0 and is
incremented for each sub-job (i.e. when numjobs option is specified). This option
is useful if there are several jobs which are intended to operate on a file in
parallel disjoint segments, with even spacing between the starting points.
Percentages can be used for this option. If a percentage is given, the generated
offset will be aligned to the minimum blocksize or to the value of offset_align if
provided.In ZBD mode, value can be set as number of zones using 'z'.
number_ios=int
Fio will normally perform I/Os until it has exhausted the size of the region set by
size, or if it exhaust the allocated time (or hits an error condition). With this
setting, the range/size can be set independently of the number of I/Os to perform.
When fio reaches this number, it will exit normally and report status. Note that
this does not extend the amount of I/O that will be done, it will only stop fio if
this condition is met before other end-of-job criteria.
fsync=int
If writing to a file, issue an fsync(2) (or its equivalent) of the dirty data for
every number of blocks given. For example, if you give 32 as a parameter, fio will
sync the file after every 32 writes issued. If fio is using non-buffered I/O, we
may not sync the file. The exception is the sg I/O engine, which synchronizes the
disk cache anyway. Defaults to 0, which means fio does not periodically issue and
wait for a sync to complete. Also see end_fsync and fsync_on_close.
fdatasync=int
Like fsync but uses fdatasync(2) to only sync data and not metadata blocks. In
Windows, DragonFlyBSD or OSX there is no fdatasync(2) so this falls back to using
fsync(2). Defaults to 0, which means fio does not periodically issue and wait for
a data-only sync to complete.
write_barrier=int
Make every N-th write a barrier write.
sync_file_range=str:int
Use sync_file_range(2) for every int number of write operations. Fio will track
range of writes that have happened since the last sync_file_range(2) call. str can
currently be one or more of:
wait_before
SYNC_FILE_RANGE_WAIT_BEFORE
write SYNC_FILE_RANGE_WRITE
wait_after
SYNC_FILE_RANGE_WRITE_AFTER
So if you do `sync_file_range=wait_before,write:8', fio would use
`SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE' for every 8 writes. Also see
the sync_file_range(2) man page. This option is Linux specific.
overwrite=bool
If true, writes to a file will always overwrite existing data. If the file doesn't
already exist, it will be created before the write phase begins. If the file exists
and is large enough for the specified write phase, nothing will be done. Default:
false.
end_fsync=bool
If true, fsync(2) file contents when a write stage has completed. Default: false.
fsync_on_close=bool
If true, fio will fsync(2) a dirty file on close. This differs from end_fsync in
that it will happen on every file close, not just at the end of the job. Default:
false.
rwmixread=int
Percentage of a mixed workload that should be reads. Default: 50.
rwmixwrite=int
Percentage of a mixed workload that should be writes. If both rwmixread and
rwmixwrite is given and the values do not add up to 100%, the latter of the two
will be used to override the first. This may interfere with a given rate setting,
if fio is asked to limit reads or writes to a certain rate. If that is the case,
then the distribution may be skewed. Default: 50.
random_distribution=str:float[:float][,str:float][,str:float]
By default, fio will use a completely uniform random distribution when asked to
perform random I/O. Sometimes it is useful to skew the distribution in specific
ways, ensuring that some parts of the data is more hot than others. fio includes
the following distribution models:
random Uniform random distribution
zipf Zipf distribution
pareto Pareto distribution
normal Normal (Gaussian) distribution
zoned Zoned random distribution zoned_abs Zoned absolute random
distribution
When using a zipf or pareto distribution, an input value is also needed to define
the access pattern. For zipf, this is the `Zipf theta'. For pareto, it's the
`Pareto power'. Fio includes a test program, fio-genzipf, that can be used
visualize what the given input values will yield in terms of hit rates. If you
wanted to use zipf with a `theta' of 1.2, you would use
`random_distribution=zipf:1.2' as the option. If a non-uniform model is used, fio
will disable use of the random map. For the normal distribution, a normal
(Gaussian) deviation is supplied as a value between 0 and 100.
The second, optional float is allowed for pareto, zipf and normal distributions. It
allows to set base of distribution in non-default place, giving more control over
most probable outcome. This value is in range [0-1] which maps linearly to range of
possible random values. Defaults are: random for pareto and zipf, and 0.5 for
normal. If you wanted to use zipf with a `theta` of 1.2 centered on 1/4 of allowed
value range, you would use `random_distribution=zipf:1.2:0.25`.
For a zoned distribution, fio supports specifying percentages of I/O access that
should fall within what range of the file or device. For example, given a criteria
of:
60% of accesses should be to the first 10%
30% of accesses should be to the next 20%
8% of accesses should be to the next 30%
2% of accesses should be to the next 40%
we can define that through zoning of the random accesses. For the above example,
the user would do:
random_distribution=zoned:60/10:30/20:8/30:2/40
A zoned_abs distribution works exactly like thezoned, except that it takes absolute
sizes. For example, let's say you wanted to define access according to the
following criteria:
60% of accesses should be to the first 20G
30% of accesses should be to the next 100G
10% of accesses should be to the next 500G
we can define an absolute zoning distribution with:
random_distribution=zoned:60/10:30/20:8/30:2/40
For both zoned and zoned_abs, fio supports defining up to 256 separate zones.
Similarly to how bssplit works for setting ranges and percentages of block sizes.
Like bssplit, it's possible to specify separate zones for reads, writes, and trims.
If just one set is given, it'll apply to all of them.
percentage_random=int[,int][,int]
For a random workload, set how big a percentage should be random. This defaults to
100%, in which case the workload is fully random. It can be set from anywhere from
0 to 100. Setting it to 0 would make the workload fully sequential. Any setting in
between will result in a random mix of sequential and random I/O, at the given
percentages. Comma-separated values may be specified for reads, writes, and trims
as described in blocksize.
norandommap
Normally fio will cover every block of the file when doing random I/O. If this
option is given, fio will just get a new random offset without looking at past I/O
history. This means that some blocks may not be read or written, and that some
blocks may be read/written more than once. If this option is used with verify and
multiple blocksizes (via bsrange), only intact blocks are verified, i.e.,
partially-overwritten blocks are ignored. With an async I/O engine and an I/O
depth > 1, it is possible for the same block to be overwritten, which can cause
verification errors. Either do not use norandommap in this case, or also use the
lfsr random generator.
softrandommap=bool
See norandommap. If fio runs with the random block map enabled and it fails to
allocate the map, if this option is set it will continue without a random block
map. As coverage will not be as complete as with random maps, this option is
disabled by default.
random_generator=str
Fio supports the following engines for generating I/O offsets for random I/O:
tausworthe
Strong 2^88 cycle random number generator.
lfsr Linear feedback shift register generator.
tausworthe64
Strong 64-bit 2^258 cycle random number generator.
tausworthe is a strong random number generator, but it requires tracking on the
side if we want to ensure that blocks are only read or written once. lfsr
guarantees that we never generate the same offset twice, and it's also less
computationally expensive. It's not a true random generator, however, though for
I/O purposes it's typically good enough. lfsr only works with single block sizes,
not with workloads that use multiple block sizes. If used with such a workload, fio
may read or write some blocks multiple times. The default value is tausworthe,
unless the required space exceeds 2^32 blocks. If it does, then tausworthe64 is
selected automatically.
Block size
blocksize=int[,int][,int], bs=int[,int][,int]
The block size in bytes used for I/O units. Default: 4096. A single value applies
to reads, writes, and trims. Comma-separated values may be specified for reads,
writes, and trims. A value not terminated in a comma applies to subsequent types.
Examples:
bs=256k means 256k for reads, writes and trims.
bs=8k,32k means 8k for reads, 32k for writes and trims.
bs=8k,32k, means 8k for reads, 32k for writes, and default for trims.
bs=,8k means default for reads, 8k for writes and trims.
bs=,8k, means default for reads, 8k for writes, and default for
trims.
blocksize_range=irange[,irange][,irange], bsrange=irange[,irange][,irange]
A range of block sizes in bytes for I/O units. The issued I/O unit will always be a
multiple of the minimum size, unless blocksize_unaligned is set. Comma-separated
ranges may be specified for reads, writes, and trims as described in blocksize.
Example:
bsrange=1k-4k,2k-8k
bssplit=str[,str][,str]
Sometimes you want even finer grained control of the block sizes issued, not just
an even split between them. This option allows you to weight various block sizes,
so that you are able to define a specific amount of block sizes issued. The format
for this option is:
bssplit=blocksize/percentage:blocksize/percentage
for as many block sizes as needed. So if you want to define a workload that has 50%
64k blocks, 10% 4k blocks, and 40% 32k blocks, you would write:
bssplit=4k/10:64k/50:32k/40
Ordering does not matter. If the percentage is left blank, fio will fill in the
remaining values evenly. So a bssplit option like this one:
bssplit=4k/50:1k/:32k/
would have 50% 4k ios, and 25% 1k and 32k ios. The percentages always add up to
100, if bssplit is given a range that adds up to more, it will error out.
Comma-separated values may be specified for reads, writes, and trims as described
in blocksize.
If you want a workload that has 50% 2k reads and 50% 4k reads, while having 90% 4k
writes and 10% 8k writes, you would specify:
bssplit=2k/50:4k/50,4k/90:8k/10
Fio supports defining up to 64 different weights for each data direction.
blocksize_unaligned, bs_unaligned
If set, fio will issue I/O units with any size within blocksize_range, not just
multiples of the minimum size. This typically won't work with direct I/O, as that
normally requires sector alignment.
bs_is_seq_rand=bool
If this option is set, fio will use the normal read,write blocksize settings as
sequential,random blocksize settings instead. Any random read or write will use the
WRITE blocksize settings, and any sequential read or write will use the READ
blocksize settings.
blockalign=int[,int][,int], ba=int[,int][,int]
Boundary to which fio will align random I/O units. Default: blocksize. Minimum
alignment is typically 512b for using direct I/O, though it usually depends on the
hardware block size. This option is mutually exclusive with using a random map for
files, so it will turn off that option. Comma-separated values may be specified for
reads, writes, and trims as described in blocksize.
Buffers and memory
zero_buffers
Initialize buffers with all zeros. Default: fill buffers with random data.
refill_buffers
If this option is given, fio will refill the I/O buffers on every submit. The
default is to only fill it at init time and reuse that data. Only makes sense if
zero_buffers isn't specified, naturally. If data verification is enabled,
refill_buffers is also automatically enabled.
scramble_buffers=bool
If refill_buffers is too costly and the target is using data deduplication, then
setting this option will slightly modify the I/O buffer contents to defeat normal
de-dupe attempts. This is not enough to defeat more clever block compression
attempts, but it will stop naive dedupe of blocks. Default: true.
buffer_compress_percentage=int
If this is set, then fio will attempt to provide I/O buffer content (on WRITEs)
that compresses to the specified level. Fio does this by providing a mix of random
data followed by fixed pattern data. The fixed pattern is either zeros, or the
pattern specified by buffer_pattern. If the buffer_pattern option is used, it might
skew the compression ratio slightly. Setting buffer_compress_percentage to a value
other than 100 will also enable refill_buffers in order to reduce the likelihood
that adjacent blocks are so similar that they over compress when seen together. See
buffer_compress_chunk for how to set a finer or coarser granularity of the
random/fixed data regions. Defaults to unset i.e., buffer data will not adhere to
any compression level.
buffer_compress_chunk=int
This setting allows fio to manage how big the random/fixed data region is when
using buffer_compress_percentage. When buffer_compress_chunk is set to some non-
zero value smaller than the block size, fio can repeat the random/fixed region
throughout the I/O buffer at the specified interval (which particularly useful when
bigger block sizes are used for a job). When set to 0, fio will use a chunk size
that matches the block size resulting in a single random/fixed region within the
I/O buffer. Defaults to 512. When the unit is omitted, the value is interpreted in
bytes.
buffer_pattern=str
If set, fio will fill the I/O buffers with this pattern or with the contents of a
file. If not set, the contents of I/O buffers are defined by the other options
related to buffer contents. The setting can be any pattern of bytes, and can be
prefixed with 0x for hex values. It may also be a string, where the string must
then be wrapped with "". Or it may also be a filename, where the filename must be
wrapped with '' in which case the file is opened and read. Note that not all the
file contents will be read if that would cause the buffers to overflow. So, for
example:
buffer_pattern='filename'
or:
buffer_pattern="abcd"
or:
buffer_pattern=-12
or:
buffer_pattern=0xdeadface
Also you can combine everything together in any order:
buffer_pattern=0xdeadface"abcd"-12'filename'
dedupe_percentage=int
If set, fio will generate this percentage of identical buffers when writing. These
buffers will be naturally dedupable. The contents of the buffers depend on what
other buffer compression settings have been set. It's possible to have the
individual buffers either fully compressible, or not at all -- this option only
controls the distribution of unique buffers. Setting this option will also enable
refill_buffers to prevent every buffer being identical.
dedupe_mode=str
If dedupe_percentage is given, then this option controls how fio generates the
dedupe buffers.
repeat
Generate dedupe buffers by repeating previous writes
working_set
Generate dedupe buffers from working set
repeat is the default option for fio. Dedupe buffers are generated by repeating
previous unique write.
working_set is a more realistic workload. With working_set,
dedupe_working_set_percentage should be provided. Given that, fio will use the
initial unique write buffers as its working set. Upon deciding to dedupe, fio will
randomly choose a buffer from the working set. Note that by using working_set the
dedupe percentage will converge to the desired over time while repeat maintains the
desired percentage throughout the job.
dedupe_working_set_percentage=int
If dedupe_mode is set to working_set, then this controls the percentage of size of
the file or device used as the buffers fio will choose to generate the dedupe
buffers from
Note that size needs to be explicitly provided and only 1 file per job is supported
invalidate=bool
Invalidate the buffer/page cache parts of the files to be used prior to starting
I/O if the platform and file type support it. Defaults to true. This will be
ignored if pre_read is also specified for the same job.
sync=str
Whether, and what type, of synchronous I/O to use for writes. The allowed values
are:
none Do not use synchronous IO, the default.
0 Same as none.
sync Use synchronous file IO. For the majority of I/O engines, this means
using O_SYNC.
1 Same as sync.
dsync Use synchronous data IO. For the majority of I/O engines, this means
using O_DSYNC.
iomem=str, mem=str
Fio can use various types of memory as the I/O unit buffer. The allowed values are:
malloc Use memory from malloc(3) as the buffers. Default memory type.
shm Use shared memory as the buffers. Allocated through shmget(2).
shmhuge
Same as shm, but use huge pages as backing.
mmap Use mmap(2) to allocate buffers. May either be anonymous memory, or
can be file backed if a filename is given after the option. The
format is `mem=mmap:/path/to/file'.
mmaphuge
Use a memory mapped huge file as the buffer backing. Append filename
after mmaphuge, ala `mem=mmaphuge:/hugetlbfs/file'.
mmapshared
Same as mmap, but use a MMAP_SHARED mapping.
cudamalloc
Use GPU memory as the buffers for GPUDirect RDMA benchmark. The
ioengine must be rdma.
The area allocated is a function of the maximum allowed bs size for the job,
multiplied by the I/O depth given. Note that for shmhuge and mmaphuge to work, the
system must have free huge pages allocated. This can normally be checked and set by
reading/writing `/proc/sys/vm/nr_hugepages' on a Linux system. Fio assumes a huge
page is 4MiB in size. So to calculate the number of huge pages you need for a given
job file, add up the I/O depth of all jobs (normally one unless iodepth is used)
and multiply by the maximum bs set. Then divide that number by the huge page size.
You can see the size of the huge pages in `/proc/meminfo'. If no huge pages are
allocated by having a non-zero number in `nr_hugepages', using mmaphuge or shmhuge
will fail. Also see hugepage-size.
mmaphuge also needs to have hugetlbfs mounted and the file location should point
there. So if it's mounted in `/huge', you would use `mem=mmaphuge:/huge/somefile'.
iomem_align=int, mem_align=int
This indicates the memory alignment of the I/O memory buffers. Note that the given
alignment is applied to the first I/O unit buffer, if using iodepth the alignment
of the following buffers are given by the bs used. In other words, if using a bs
that is a multiple of the page sized in the system, all buffers will be aligned to
this value. If using a bs that is not page aligned, the alignment of subsequent I/O
memory buffers is the sum of the iomem_align and bs used.
hugepage-size=int
Defines the size of a huge page. Must at least be equal to the system setting, see
`/proc/meminfo'. Defaults to 4MiB. Should probably always be a multiple of
megabytes, so using `hugepage-size=Xm' is the preferred way to set this to avoid
setting a non-pow-2 bad value.
lockmem=int
Pin the specified amount of memory with mlock(2). Can be used to simulate a smaller
amount of memory. The amount specified is per worker.
I/O size
size=int[%|z]
The total size of file I/O for each thread of this job. Fio will run until this
many bytes has been transferred, unless runtime is limited by other options (such
as runtime, for instance, or increased/decreased by io_size). Fio will divide this
size between the available files determined by options such as nrfiles, filename,
unless filesize is specified by the job. If the result of division happens to be 0,
the size is set to the physical size of the given files or devices if they exist.
If this option is not specified, fio will use the full size of the given files or
devices. If the files do not exist, size must be given. It is also possible to give
size as a percentage between 1 and 100. If `size=20%' is given, fio will use 20% of
the full size of the given files or devices. In ZBD mode, size can be given in
units of number of zones using 'z'. Can be combined with offset to constrain the
start and end range that I/O will be done within.
io_size=int[%|z], io_limit=int[%|z]
Normally fio operates within the region set by size, which means that the size
option sets both the region and size of I/O to be performed. Sometimes that is not
what you want. With this option, it is possible to define just the amount of I/O
that fio should do. For instance, if size is set to 20GiB and io_size is set to
5GiB, fio will perform I/O within the first 20GiB but exit when 5GiB have been
done. The opposite is also possible -- if size is set to 20GiB, and io_size is set
to 40GiB, then fio will do 40GiB of I/O within the 0..20GiB region. Value can be
set as percentage: io_size=N%. In this case io_size multiplies size= value. In ZBD
mode, value can also be set as number of zones using 'z'.
filesize=irange(int)
Individual file sizes. May be a range, in which case fio will select sizes for
files at random within the given range. If not given, each created file is the same
size. This option overrides size in terms of file size, i.e. size becomes merely
the default for io_size (and has no effect it all if io_size is set explicitly).
file_append=bool
Perform I/O after the end of the file. Normally fio will operate within the size of
a file. If this option is set, then fio will append to the file instead. This has
identical behavior to setting offset to the size of a file. This option is ignored
on non-regular files.
fill_device=bool, fill_fs=bool
Sets size to something really large and waits for ENOSPC (no space left on device)
or EDQUOT (disk quota exceeded) as the terminating condition. Only makes sense with
sequential write. For a read workload, the mount point will be filled first then
I/O started on the result.
I/O engine
ioengine=str
Defines how the job issues I/O to the file. The following types are defined:
sync Basic read(2) or write(2) I/O. lseek(2) is used to position the I/O
location. See fsync and fdatasync for syncing write I/Os.
psync Basic pread(2) or pwrite(2) I/O. Default on all supported operating
systems except for Windows.
vsync Basic readv(2) or writev(2) I/O. Will emulate queuing by coalescing
adjacent I/Os into a single submission.
pvsync Basic preadv(2) or pwritev(2) I/O.
pvsync2
Basic preadv2(2) or pwritev2(2) I/O.
libaio Linux native asynchronous I/O. Note that Linux may only support
queued behavior with non-buffered I/O (set `direct=1' or
`buffered=0'). This engine defines engine specific options.
posixaio
POSIX asynchronous I/O using aio_read(3) and aio_write(3).
solarisaio
Solaris native asynchronous I/O.
windowsaio
Windows native asynchronous I/O. Default on Windows.
mmap File is memory mapped with mmap(2) and data copied to/from using
memcpy(3).
splice splice(2) is used to transfer the data and vmsplice(2) to transfer
data from user space to the kernel.
sg SCSI generic sg v3 I/O. May either be synchronous using the SG_IO
ioctl, or if the target is an sg character device we use read(2) and
write(2) for asynchronous I/O. Requires filename option to specify
either block or character devices. This engine supports trim
operations. The sg engine includes engine specific options.
libzbc Read, write, trim and ZBC/ZAC operations to a zoned block device
using libzbc library. The target can be either an SG character device
or a block device file.
null Doesn't transfer any data, just pretends to. This is mainly used to
exercise fio itself and for debugging/testing purposes.
net Transfer over the network to given `host:port'. Depending on the
protocol used, the hostname, port, listen and filename options are
used to specify what sort of connection to make, while the protocol
option determines which protocol will be used. This engine defines
engine specific options.
netsplice
Like net, but uses splice(2) and vmsplice(2) to map data and
send/receive. This engine defines engine specific options.
cpuio Doesn't transfer any data, but burns CPU cycles according to the
cpuload, cpuchunks and cpumode options. A job never finishes unless
there is at least one non-cpuio job.
cpuload=85 will cause that job to do nothing but burn 85% of the CPU.
In case of SMP machines, use numjobs=<nr_of_cpu> to get desired CPU
usage, as the cpuload only loads a single CPU at the desired rate.
cpumode=qsort replace the default noop instructions loop by a qsort
algorithm to consume more energy.
rdma The RDMA I/O engine supports both RDMA memory semantics
(RDMA_WRITE/RDMA_READ) and channel semantics (Send/Recv) for the
InfiniBand, RoCE and iWARP protocols. This engine defines engine
specific options.
falloc I/O engine that does regular fallocate to simulate data transfer as
fio ioengine.
DDIR_READ does fallocate(,mode = FALLOC_FL_KEEP_SIZE,).
DIR_WRITE does fallocate(,mode = 0).
DDIR_TRIM does fallocate(,mode =
FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE).
ftruncate
I/O engine that sends ftruncate(2) operations in response to write
(DDIR_WRITE) events. Each ftruncate issued sets the file's size to
the current block offset. blocksize is ignored.
e4defrag
I/O engine that does regular EXT4_IOC_MOVE_EXT ioctls to simulate
defragment activity in request to DDIR_WRITE event.
rados I/O engine supporting direct access to Ceph Reliable Autonomic
Distributed Object Store (RADOS) via librados. This ioengine defines
engine specific options.
rbd I/O engine supporting direct access to Ceph Rados Block Devices (RBD)
via librbd without the need to use the kernel rbd driver. This
ioengine defines engine specific options.
http I/O engine supporting GET/PUT requests over HTTP(S) with libcurl to a
WebDAV or S3 endpoint. This ioengine defines engine specific
options.
This engine only supports direct IO of iodepth=1; you need to scale
this via numjobs. blocksize defines the size of the objects to be
created.
TRIM is translated to object deletion.
gfapi Using GlusterFS libgfapi sync interface to direct access to GlusterFS
volumes without having to go through FUSE. This ioengine defines
engine specific options.
gfapi_async
Using GlusterFS libgfapi async interface to direct access to
GlusterFS volumes without having to go through FUSE. This ioengine
defines engine specific options.
libhdfs
Read and write through Hadoop (HDFS). The filename option is used to
specify host,port of the hdfs name-node to connect. This engine
interprets offsets a little differently. In HDFS, files once created
cannot be modified so random writes are not possible. To imitate this
the libhdfs engine expects a bunch of small files to be created over
HDFS and will randomly pick a file from them based on the offset
generated by fio backend (see the example job file to create such
files, use `rw=write' option). Please note, it may be necessary to
set environment variables to work with HDFS/libhdfs properly. Each
job uses its own connection to HDFS.
mtd Read, write and erase an MTD character device (e.g., `/dev/mtd0').
Discards are treated as erases. Depending on the underlying device
type, the I/O may have to go in a certain pattern, e.g., on NAND,
writing sequentially to erase blocks and discarding before
overwriting. The trimwrite mode works well for this constraint.
pmemblk
Read and write using filesystem DAX to a file on a filesystem mounted
with DAX on a persistent memory device through the PMDK libpmemblk
library.
dev-dax
Read and write using device DAX to a persistent memory device (e.g.,
/dev/dax0.0) through the PMDK libpmem library.
external
Prefix to specify loading an external I/O engine object file. Append
the engine filename, e.g. `ioengine=external:/tmp/foo.o' to load
ioengine `foo.o' in `/tmp'. The path can be either absolute or
relative. See `engines/skeleton_external.c' in the fio source for
details of writing an external I/O engine.
filecreate
Simply create the files and do no I/O to them. You still need to set
filesize so that all the accounting still occurs, but no actual I/O
will be done other than creating the file.
filestat
Simply do stat() and do no I/O to the file. You need to set
'filesize' and 'nrfiles', so that files will be created. This engine
is to measure file lookup and meta data access.
filedelete
Simply delete files by unlink() and do no I/O to the file. You need
to set 'filesize' and 'nrfiles', so that files will be created. This
engine is to measure file delete.
libpmem
Read and write using mmap I/O to a file on a filesystem mounted with
DAX on a persistent memory device through the PMDK libpmem library.
ime_psync
Synchronous read and write using DDN's Infinite Memory Engine (IME).
This engine is very basic and issues calls to IME whenever an IO is
queued.
ime_psyncv
Synchronous read and write using DDN's Infinite Memory Engine (IME).
This engine uses iovecs and will try to stack as much IOs as possible
(if the IOs are "contiguous" and the IO depth is not exceeded) before
issuing a call to IME.
ime_aio
Asynchronous read and write using DDN's Infinite Memory Engine (IME).
This engine will try to stack as much IOs as possible by creating
requests for IME. FIO will then decide when to commit these
requests.
libiscsi
Read and write iscsi lun with libiscsi.
nbd Synchronous read and write a Network Block Device (NBD).
libcufile
I/O engine supporting libcufile synchronous access to nvidia-fs and a
GPUDirect Storage-supported filesystem. This engine performs I/O
without transferring buffers between user-space and the kernel,
unless verify is set or cuda_io is posix. iomem must not be
cudamalloc. This ioengine defines engine specific options.
dfs I/O engine supporting asynchronous read and write operations to the
DAOS File System (DFS) via libdfs.
nfs I/O engine supporting asynchronous read and write operations to NFS
filesystems from userspace via libnfs. This is useful for achieving
higher concurrency and thus throughput than is possible via kernel
NFS.
exec Execute 3rd party tools. Could be used to perform monitoring during
jobs runtime.
I/O engine specific parameters
In addition, there are some parameters which are only valid when a specific ioengine is in
use. These are used identically to normal parameters, with the caveat that when used on
the command line, they must come after the ioengine that defines them is selected.
(io_uring,libaio)cmdprio_percentage=int[,int]
Set the percentage of I/O that will be issued with the highest priority. Default:
0. A single value applies to reads and writes. Comma-separated values may be
specified for reads and writes. For this option to be effective, NCQ priority must
be supported and enabled, and `direct=1' option must be used. fio must also be run
as the root user. Unlike slat/clat/lat stats, which can be tracked and reported
independently, per priority stats only track and report a single type of latency.
By default, completion latency (clat) will be reported, if lat_percentiles is set,
total latency (lat) will be reported.
(io_uring,libaio)cmdprio_class=int[,int]
Set the I/O priority class to use for I/Os that must be issued with a priority when
cmdprio_percentage or cmdprio_bssplit is set. If not specified when
cmdprio_percentage or cmdprio_bssplit is set, this defaults to the highest priority
class. A single value applies to reads and writes. Comma-separated values may be
specified for reads and writes. See man ionice(1). See also the prioclass option.
(io_uring,libaio)cmdprio=int[,int]
Set the I/O priority value to use for I/Os that must be issued with a priority when
cmdprio_percentage or cmdprio_bssplit is set. If not specified when
cmdprio_percentage or cmdprio_bssplit is set, this defaults to 0. Linux limits us
to a positive value between 0 and 7, with 0 being the highest. A single value
applies to reads and writes. Comma-separated values may be specified for reads and
writes. See man ionice(1). Refer to an appropriate manpage for other operating
systems since the meaning of priority may differ. See also the prio option.
(io_uring,libaio)cmdprio_bssplit=str[,str]
To get a finer control over I/O priority, this option allows specifying the
percentage of IOs that must have a priority set depending on the block size of the
IO. This option is useful only when used together with the option bssplit, that is,
multiple different block sizes are used for reads and writes.
The first accepted format for this option is the same as the format of the bssplit
option:
cmdprio_bssplit=blocksize/percentage:blocksize/percentage
In this case, each entry will use the priority class and priority level defined by
the options cmdprio_class and cmdprio respectively.
The second accepted format for this option is:
cmdprio_bssplit=blocksize/percentage/class/level:blocksize/percentage/class/level
In this case, the priority class and priority level is defined inside each entry.
In comparison with the first accepted format, the second accepted format does not
restrict all entries to have the same priority class and priority level.
For both formats, only the read and write data directions are supported, values for
trim IOs are ignored. This option is mutually exclusive with the cmdprio_percentage
option.
(io_uring)fixedbufs
If fio is asked to do direct IO, then Linux will map pages for each IO call, and
release them when IO is done. If this option is set, the pages are pre-mapped
before IO is started. This eliminates the need to map and release for each IO.
This is more efficient, and reduces the IO latency as well.
(io_uring)hipri
If this option is set, fio will attempt to use polled IO completions. Normal IO
completions generate interrupts to signal the completion of IO, polled completions
do not. Hence they are require active reaping by the application. The benefits are
more efficient IO for high IOPS scenarios, and lower latencies for low queue depth
IO.
(io_uring)registerfiles
With this option, fio registers the set of files being used with the kernel. This
avoids the overhead of managing file counts in the kernel, making the submission
and completion part more lightweight. Required for the below sqthread_poll option.
(io_uring)sqthread_poll
Normally fio will submit IO by issuing a system call to notify the kernel of
available items in the SQ ring. If this option is set, the act of submitting IO
will be done by a polling thread in the kernel. This frees up cycles for fio, at
the cost of using more CPU in the system.
(io_uring)sqthread_poll_cpu
When `sqthread_poll` is set, this option provides a way to define which CPU should
be used for the polling thread.
(libaio)userspace_reap
Normally, with the libaio engine in use, fio will use the io_getevents(3) system
call to reap newly returned events. With this flag turned on, the AIO ring will be
read directly from user-space to reap events. The reaping mode is only enabled when
polling for a minimum of 0 events (e.g. when `iodepth_batch_complete=0').
(pvsync2)hipri
Set RWF_HIPRI on I/O, indicating to the kernel that it's of higher priority than
normal.
(pvsync2)hipri_percentage
When hipri is set this determines the probability of a pvsync2 I/O being high
priority. The default is 100%.
(pvsync2,libaio,io_uring)nowait
By default if a request cannot be executed immediately (e.g. resource starvation,
waiting on locks) it is queued and the initiating process will be blocked until the
required resource becomes free. This option sets the RWF_NOWAIT flag (supported
from the 4.14 Linux kernel) and the call will return instantly with EAGAIN or a
partial result rather than waiting.
It is useful to also use ignore_error=EAGAIN when using this option. Note: glibc
2.27, 2.28 have a bug in syscall wrappers preadv2, pwritev2. They return EOPNOTSUP
instead of EAGAIN.
For cached I/O, using this option usually means a request operates only with cached
data. Currently the RWF_NOWAIT flag does not supported for cached write. For
direct I/O, requests will only succeed if cache invalidation isn't required, file
blocks are fully allocated and the disk request could be issued immediately.
(cpuio)cpuload=int
Attempt to use the specified percentage of CPU cycles. This is a mandatory option
when using cpuio I/O engine.
(cpuio)cpuchunks=int
Split the load into cycles of the given time. In microseconds.
(cpuio)cpumode=str
Specify how to stress the CPU. It can take these two values:
noop This is the default and directs the CPU to execute noop instructions.
qsort Replace the default noop instructions with a qsort algorithm to
consume more energy.
(cpuio)exit_on_io_done=bool
Detect when I/O threads are done, then exit.
(libhdfs)namenode=str
The hostname or IP address of a HDFS cluster namenode to contact.
(libhdfs)port=int
The listening port of the HFDS cluster namenode.
(netsplice,net)port=int
The TCP or UDP port to bind to or connect to. If this is used with numjobs to spawn
multiple instances of the same job type, then this will be the starting port number
since fio will use a range of ports.
(rdma,librpma_*)port=int
The port to use for RDMA-CM communication. This should be the same value on the
client and the server side.
(netsplice,net,rdma)hostname=str
The hostname or IP address to use for TCP, UDP or RDMA-CM based I/O. If the job is
a TCP listener or UDP reader, the hostname is not used and must be omitted unless
it is a valid UDP multicast address.
(librpma_*)serverip=str
The IP address to be used for RDMA-CM based I/O.
(librpma_*_server)direct_write_to_pmem=bool
Set to 1 only when Direct Write to PMem from the remote host is possible.
Otherwise, set to 0.
(librpma_*_server)busy_wait_polling=bool
Set to 0 to wait for completion instead of busy-wait polling completion. Default:
1.
(netsplice,net)interface=str
The IP address of the network interface used to send or receive UDP multicast.
(netsplice,net)ttl=int
Time-to-live value for outgoing UDP multicast packets. Default: 1.
(netsplice,net)nodelay=bool
Set TCP_NODELAY on TCP connections.
(netsplice,net)protocol=str, proto=str
The network protocol to use. Accepted values are:
tcp Transmission control protocol.
tcpv6 Transmission control protocol V6.
udp User datagram protocol.
udpv6 User datagram protocol V6.
unix UNIX domain socket.
When the protocol is TCP or UDP, the port must also be given, as well as the
hostname if the job is a TCP listener or UDP reader. For unix sockets, the normal
filename option should be used and the port is invalid.
(netsplice,net)listen
For TCP network connections, tell fio to listen for incoming connections rather
than initiating an outgoing connection. The hostname must be omitted if this option
is used.
(netsplice,net)pingpong
Normally a network writer will just continue writing data, and a network reader
will just consume packages. If `pingpong=1' is set, a writer will send its normal
payload to the reader, then wait for the reader to send the same payload back. This
allows fio to measure network latencies. The submission and completion latencies
then measure local time spent sending or receiving, and the completion latency
measures how long it took for the other end to receive and send back. For UDP
multicast traffic `pingpong=1' should only be set for a single reader when multiple
readers are listening to the same address.
(netsplice,net)window_size=int
Set the desired socket buffer size for the connection.
(netsplice,net)mss=int
Set the TCP maximum segment size (TCP_MAXSEG).
(e4defrag)donorname=str
File will be used as a block donor (swap extents between files).
(e4defrag)inplace=int
Configure donor file blocks allocation strategy:
0 Default. Preallocate donor's file on init.
1 Allocate space immediately inside defragment event, and free right
after event.
(rbd,rados)clustername=str
Specifies the name of the Ceph cluster.
(rbd)rbdname=str
Specifies the name of the RBD.
(rbd,rados)pool=str
Specifies the name of the Ceph pool containing RBD or RADOS data.
(rbd,rados)clientname=str
Specifies the username (without the 'client.' prefix) used to access the Ceph
cluster. If the clustername is specified, the clientname shall be the full
*type.id* string. If no type. prefix is given, fio will add 'client.' by default.
(rbd,rados)busy_poll=bool
Poll store instead of waiting for completion. Usually this provides better
throughput at cost of higher(up to 100%) CPU utilization.
(rados)touch_objects=bool
During initialization, touch (create if do not exist) all objects (files).
Touching all objects affects ceph caches and likely impacts test results. Enabled
by default.
(http)http_host=str
Hostname to connect to. For S3, this could be the bucket name. Default is localhost
(http)http_user=str
Username for HTTP authentication.
(http)http_pass=str
Password for HTTP authentication.
(http)https=str
Whether to use HTTPS instead of plain HTTP. on enables HTTPS; insecure will enable
HTTPS, but disable SSL peer verification (use with caution!). Default is off.
(http)http_mode=str
Which HTTP access mode to use: webdav, swift, or s3. Default is webdav.
(http)http_s3_region=str
The S3 region/zone to include in the request. Default is us-east-1.
(http)http_s3_key=str
The S3 secret key.
(http)http_s3_keyid=str
The S3 key/access id.
(http)http_swift_auth_token=str
The Swift auth token. See the example configuration file on how to retrieve this.
(http)http_verbose=int
Enable verbose requests from libcurl. Useful for debugging. 1 turns on verbose
logging from libcurl, 2 additionally enables HTTP IO tracing. Default is 0
(mtd)skip_bad=bool
Skip operations against known bad blocks.
(libhdfs)hdfsdirectory
libhdfs will create chunk in this HDFS directory.
(libhdfs)chunk_size
The size of the chunk to use for each file.
(rdma)verb=str
The RDMA verb to use on this side of the RDMA ioengine connection. Valid values are
write, read, send and recv. These correspond to the equivalent RDMA verbs (e.g.
write = rdma_write etc.). Note that this only needs to be specified on the client
side of the connection. See the examples folder.
(rdma)bindname=str
The name to use to bind the local RDMA-CM connection to a local RDMA device. This
could be a hostname or an IPv4 or IPv6 address. On the server side this will be
passed into the rdma_bind_addr() function and on the client site it will be used in
the rdma_resolve_add() function. This can be useful when multiple paths exist
between the client and the server or in certain loopback configurations.
(filestat)stat_type=str
Specify stat system call type to measure lookup/getattr performance. Default is
stat for stat(2).
(sg)hipri
If this option is set, fio will attempt to use polled IO completions. This will
have a similar effect as (io_uring)hipri. Only SCSI READ and WRITE commands will
have the SGV4_FLAG_HIPRI set (not UNMAP (trim) nor VERIFY). Older versions of the
Linux sg driver that do not support hipri will simply ignore this flag and do
normal IO. The Linux SCSI Low Level Driver (LLD) that "owns" the device also needs
to support hipri (also known as iopoll and mq_poll). The MegaRAID driver is an
example of a SCSI LLD. Default: clear (0) which does normal (interrupted based)
IO.
(sg)readfua=bool
With readfua option set to 1, read operations include the force unit access (fua)
flag. Default: 0.
(sg)writefua=bool
With writefua option set to 1, write operations include the force unit access (fua)
flag. Default: 0.
(sg)sg_write_mode=str
Specify the type of write commands to issue. This option can take multiple values:
write (default)
Write opcodes are issued as usual
write_and_verify
Issue WRITE AND VERIFY commands. The BYTCHK bit is set to 00b. This
directs the device to carry out a medium verification with no data
comparison for the data that was written. The writefua option is
ignored with this selection.
verify This option is deprecated. Use write_and_verify instead.
write_same
Issue WRITE SAME commands. This transfers a single block to the
device and writes this same block of data to a contiguous sequence of
LBAs beginning at the specified offset. fio's block size parameter
specifies the amount of data written with each command. However, the
amount of data actually transferred to the device is equal to the
device's block (sector) size. For a device with 512 byte sectors,
blocksize=8k will write 16 sectors with each command. fio will still
generate 8k of data for each command butonly the first 512 bytes will
be used and transferred to the device. The writefua option is ignored
with this selection.
same This option is deprecated. Use write_same instead.
write_same_ndob
Issue WRITE SAME(16) commands as above but with the No Data Output
Buffer (NDOB) bit set. No data will be transferred to the device with
this bit set. Data written will be a pre-determined pattern such as
all zeroes.
write_stream
Issue WRITE STREAM(16) commands. Use the stream_id option to specify
the stream identifier.
verify_bytchk_00
Issue VERIFY commands with BYTCHK set to 00. This directs the device
to carry out a medium verification with no data comparison.
verify_bytchk_01
Issue VERIFY commands with BYTCHK set to 01. This directs the device
to compare the data on the device with the data transferred to the
device.
verify_bytchk_11
Issue VERIFY commands with BYTCHK set to 11. This transfers a single
block to the device and compares the contents of this block with the
data on the device beginning at the specified offset. fio's block
size parameter specifies the total amount of data compared with this
command. However, only one block (sector) worth of data is
transferred to the device. This is similar to the WRITE SAME command
except that data is compared instead of written.
(sg)stream_id=int
Set the stream identifier for WRITE STREAM commands. If this is set to 0 (which is
not a valid stream identifier) fio will open a stream and then close it when done.
Default is 0.
(nbd)uri=str
Specify the NBD URI of the server to test. The string is a standard NBD URI (see
https://github.com/NetworkBlockDevice/nbd/tree/master/doc). Example URIs:
nbd://localhost:10809
nbd+unix:///?socket=/tmp/socket
nbds://tlshost/exportname
(libcufile)gpu_dev_ids=str
Specify the GPU IDs to use with CUDA. This is a colon-separated list of int. GPUs
are assigned to workers roundrobin. Default is 0.
(libcufile)cuda_io=str
Specify the type of I/O to use with CUDA. This option takes the following values:
cufile (default)
Use libcufile and nvidia-fs. This option performs I/O directly
between a GPUDirect Storage filesystem and GPU buffers, avoiding use
of a bounce buffer. If verify is set, cudaMemcpy is used to copy
verification data between RAM and GPU(s). Verification data is
copied from RAM to GPU before a write and from GPU to RAM after a
read. direct must be 1.
posix Use POSIX to perform I/O with a RAM buffer, and use cudaMemcpy to
transfer data between RAM and the GPU(s). Data is copied from GPU to
RAM before a write and copied from RAM to GPU after a read. verify
does not affect the use of cudaMemcpy.
(dfs)pool
Specify the label or UUID of the DAOS pool to connect to.
(dfs)cont
Specify the label or UUID of the DAOS container to open.
(dfs)chunk_size
Specificy a different chunk size (in bytes) for the dfs file. Use DAOS container's
chunk size by default.
(dfs)object_class
Specificy a different object class for the dfs file. Use DAOS container's object
class by default.
(nfs)nfs_url
URL in libnfs format, eg nfs://<server|ipv4|ipv6>/path[?arg=val[&arg=val]*] Refer
to the libnfs README for more details.
(exec)program=str
Specify the program to execute. Note the program will receive a SIGTERM when the
job is reaching the time limit. A SIGKILL is sent once the job is over. The delay
between the two signals is defined by grace_time option.
(exec)arguments=str
Specify arguments to pass to program. Some special variables can be expanded to
pass fio's job details to the program :
%r replaced by the duration of the job in seconds
%n replaced by the name of the job
(exec)grace_time=int
Defines the time between the SIGTERM and SIGKILL signals. Default is 1 second.
(exec)std_redirect=ool
If set, stdout and stderr streams are redirected to files named from the job name.
Default is true.
I/O depth
iodepth=int
Number of I/O units to keep in flight against the file. Note that increasing
iodepth beyond 1 will not affect synchronous ioengines (except for small degrees
when verify_async is in use). Even async engines may impose OS restrictions causing
the desired depth not to be achieved. This may happen on Linux when using libaio
and not setting `direct=1', since buffered I/O is not async on that OS. Keep an eye
on the I/O depth distribution in the fio output to verify that the achieved depth
is as expected. Default: 1.
iodepth_batch_submit=int, iodepth_batch=int
This defines how many pieces of I/O to submit at once. It defaults to 1 which means
that we submit each I/O as soon as it is available, but can be raised to submit
bigger batches of I/O at the time. If it is set to 0 the iodepth value will be
used.
iodepth_batch_complete_min=int, iodepth_batch_complete=int
This defines how many pieces of I/O to retrieve at once. It defaults to 1 which
means that we'll ask for a minimum of 1 I/O in the retrieval process from the
kernel. The I/O retrieval will go on until we hit the limit set by iodepth_low. If
this variable is set to 0, then fio will always check for completed events before
queuing more I/O. This helps reduce I/O latency, at the cost of more retrieval
system calls.
iodepth_batch_complete_max=int
This defines maximum pieces of I/O to retrieve at once. This variable should be
used along with iodepth_batch_complete_min=int variable, specifying the range of
min and max amount of I/O which should be retrieved. By default it is equal to
iodepth_batch_complete_min value. Example #1:
iodepth_batch_complete_min=1
iodepth_batch_complete_max=<iodepth>
which means that we will retrieve at least 1 I/O and up to the whole submitted
queue depth. If none of I/O has been completed yet, we will wait. Example #2:
iodepth_batch_complete_min=0
iodepth_batch_complete_max=<iodepth>
which means that we can retrieve up to the whole submitted queue depth, but if none
of I/O has been completed yet, we will NOT wait and immediately exit the system
call. In this example we simply do polling.
iodepth_low=int
The low water mark indicating when to start filling the queue again. Defaults to
the same as iodepth, meaning that fio will attempt to keep the queue full at all
times. If iodepth is set to e.g. 16 and iodepth_low is set to 4, then after fio has
filled the queue of 16 requests, it will let the depth drain down to 4 before
starting to fill it again.
serialize_overlap=bool
Serialize in-flight I/Os that might otherwise cause or suffer from data races.
When two or more I/Os are submitted simultaneously, there is no guarantee that the
I/Os will be processed or completed in the submitted order. Further, if two or more
of those I/Os are writes, any overlapping region between them can become
indeterminate/undefined on certain storage. These issues can cause verification to
fail erratically when at least one of the racing I/Os is changing data and the
overlapping region has a non-zero size. Setting serialize_overlap tells fio to
avoid provoking this behavior by explicitly serializing in-flight I/Os that have a
non-zero overlap. Note that setting this option can reduce both performance and the
iodepth achieved.
This option only applies to I/Os issued for a single job except when it is enabled
along with io_submit_mode=offload. In offload mode, fio will check for overlap
among all I/Os submitted by offload jobs with serialize_overlap enabled.
Default: false.
io_submit_mode=str
This option controls how fio submits the I/O to the I/O engine. The default is
`inline', which means that the fio job threads submit and reap I/O directly. If set
to `offload', the job threads will offload I/O submission to a dedicated pool of
I/O threads. This requires some coordination and thus has a bit of extra overhead,
especially for lower queue depth I/O where it can increase latencies. The benefit
is that fio can manage submission rates independently of the device completion
rates. This avoids skewed latency reporting if I/O gets backed up on the device
side (the coordinated omission problem). Note that this option cannot reliably be
used with async IO engines.
I/O rate
thinktime=time
Stall the job for the specified period of time after an I/O has completed before
issuing the next. May be used to simulate processing being done by an application.
When the unit is omitted, the value is interpreted in microseconds. See
thinktime_blocks, thinktime_iotime and thinktime_spin.
thinktime_spin=time
Only valid if thinktime is set - pretend to spend CPU time doing something with the
data received, before falling back to sleeping for the rest of the period specified
by thinktime. When the unit is omitted, the value is interpreted in microseconds.
thinktime_blocks=int
Only valid if thinktime is set - control how many blocks to issue, before waiting
thinktime usecs. If not set, defaults to 1 which will make fio wait thinktime usecs
after every block. This effectively makes any queue depth setting redundant, since
no more than 1 I/O will be queued before we have to complete it and do our
thinktime. In other words, this setting effectively caps the queue depth if the
latter is larger.
thinktime_blocks_type=str
Only valid if thinktime is set - control how thinktime_blocks triggers. The
default is `complete', which triggers thinktime when fio completes thinktime_blocks
blocks. If this is set to `issue', then the trigger happens at the issue side.
thinktime_iotime=time
Only valid if thinktime is set - control thinktime interval by time. The thinktime
stall is repeated after IOs are executed for thinktime_iotime. For example,
`--thinktime_iotime=9s --thinktime=1s' repeat 10-second cycle with IOs for 9
seconds and stall for 1 second. When the unit is omitted, thinktime_iotime is
interpreted as a number of seconds. If this option is used together with
thinktime_blocks, the thinktime stall is repeated after thinktime_iotime or after
thinktime_blocks IOs, whichever happens first.
rate=int[,int][,int]
Cap the bandwidth used by this job. The number is in bytes/sec, the normal suffix
rules apply. Comma-separated values may be specified for reads, writes, and trims
as described in blocksize.
For example, using `rate=1m,500k' would limit reads to 1MiB/sec and writes to
500KiB/sec. Capping only reads or writes can be done with `rate=,500k' or
`rate=500k,' where the former will only limit writes (to 500KiB/sec) and the latter
will only limit reads.
rate_min=int[,int][,int]
Tell fio to do whatever it can to maintain at least this bandwidth. Failing to meet
this requirement will cause the job to exit. Comma-separated values may be
specified for reads, writes, and trims as described in blocksize.
rate_iops=int[,int][,int]
Cap the bandwidth to this number of IOPS. Basically the same as rate, just
specified independently of bandwidth. If the job is given a block size range
instead of a fixed value, the smallest block size is used as the metric. Comma-
separated values may be specified for reads, writes, and trims as described in
blocksize.
rate_iops_min=int[,int][,int]
If fio doesn't meet this rate of I/O, it will cause the job to exit. Comma-
separated values may be specified for reads, writes, and trims as described in
blocksize.
rate_process=str
This option controls how fio manages rated I/O submissions. The default is
`linear', which submits I/O in a linear fashion with fixed delays between I/Os that
gets adjusted based on I/O completion rates. If this is set to `poisson', fio will
submit I/O based on a more real world random request flow, known as the Poisson
process (https://en.wikipedia.org/wiki/Poisson_point_process). The lambda will be
10^6 / IOPS for the given workload.
rate_ignore_thinktime=bool
By default, fio will attempt to catch up to the specified rate setting, if any kind
of thinktime setting was used. If this option is set, then fio will ignore the
thinktime and continue doing IO at the specified rate, instead of entering a catch-
up mode after thinktime is done.
I/O latency
latency_target=time
If set, fio will attempt to find the max performance point that the given workload
will run at while maintaining a latency below this target. When the unit is
omitted, the value is interpreted in microseconds. See latency_window and
latency_percentile.
latency_window=time
Used with latency_target to specify the sample window that the job is run at
varying queue depths to test the performance. When the unit is omitted, the value
is interpreted in microseconds.
latency_percentile=float
The percentage of I/Os that must fall within the criteria specified by
latency_target and latency_window. If not set, this defaults to 100.0, meaning that
all I/Os must be equal or below to the value set by latency_target.
latency_run=bool
Used with latency_target. If false (default), fio will find the highest queue depth
that meets latency_target and exit. If true, fio will continue running and try to
meet latency_target by adjusting queue depth.
max_latency=time[,time][,time]
If set, fio will exit the job with an ETIMEDOUT error if it exceeds this maximum
latency. When the unit is omitted, the value is interpreted in microseconds. Comma-
separated values may be specified for reads, writes, and trims as described in
blocksize.
rate_cycle=int
Average bandwidth for rate and rate_min over this number of milliseconds. Defaults
to 1000.
I/O replay
write_iolog=str
Write the issued I/O patterns to the specified file. See read_iolog. Specify a
separate file for each job, otherwise the iologs will be interspersed and the file
may be corrupt.
read_iolog=str
Open an iolog with the specified filename and replay the I/O patterns it contains.
This can be used to store a workload and replay it sometime later. The iolog given
may also be a blktrace binary file, which allows fio to replay a workload captured
by blktrace. See blktrace(8) for how to capture such logging data. For blktrace
replay, the file needs to be turned into a blkparse binary data file first
(`blkparse <device> -o /dev/null -d file_for_fio.bin'). You can specify a number
of files by separating the names with a ':' character. See the filename option for
information on how to escape ':' characters within the file names. These files will
be sequentially assigned to job clones created by numjobs. '-' is a reserved name,
meaning read from stdin, notably if filename is set to '-' which means stdin as
well, then this flag can't be set to '-'.
read_iolog_chunked=bool
Determines how iolog is read. If false (default) entire read_iolog will be read at
once. If selected true, input from iolog will be read gradually. Useful when iolog
is very large, or it is generated.
merge_blktrace_file=str
When specified, rather than replaying the logs passed to read_iolog, the logs go
through a merge phase which aggregates them into a single blktrace. The resulting
file is then passed on as the read_iolog parameter. The intention here is to make
the order of events consistent. This limits the influence of the scheduler compared
to replaying multiple blktraces via concurrent jobs.
merge_blktrace_scalars=float_list
This is a percentage based option that is index paired with the list of files
passed to read_iolog. When merging is performed, scale the time of each event by
the corresponding amount. For example, `--merge_blktrace_scalars="50:100"' runs the
first trace in halftime and the second trace in realtime. This knob is separately
tunable from replay_time_scale which scales the trace during runtime and will not
change the output of the merge unlike this option.
merge_blktrace_iters=float_list
This is a whole number option that is index paired with the list of files passed to
read_iolog. When merging is performed, run each trace for the specified number of
iterations. For example, `--merge_blktrace_iters="2:1"' runs the first trace for
two iterations and the second trace for one iteration.
replay_no_stall=bool
When replaying I/O with read_iolog the default behavior is to attempt to respect
the timestamps within the log and replay them with the appropriate delay between
IOPS. By setting this variable fio will not respect the timestamps and attempt to
replay them as fast as possible while still respecting ordering. The result is the
same I/O pattern to a given device, but different timings.
replay_time_scale=int
When replaying I/O with read_iolog, fio will honor the original timing in the
trace. With this option, it's possible to scale the time. It's a percentage option,
if set to 50 it means run at 50% the original IO rate in the trace. If set to 200,
run at twice the original IO rate. Defaults to 100.
replay_redirect=str
While replaying I/O patterns using read_iolog the default behavior is to replay the
IOPS onto the major/minor device that each IOP was recorded from. This is sometimes
undesirable because on a different machine those major/minor numbers can map to a
different device. Changing hardware on the same system can also result in a
different major/minor mapping. replay_redirect causes all I/Os to be replayed onto
the single specified device regardless of the device it was recorded from. i.e.
`replay_redirect=/dev/sdc' would cause all I/O in the blktrace or iolog to be
replayed onto `/dev/sdc'. This means multiple devices will be replayed onto a
single device, if the trace contains multiple devices. If you want multiple devices
to be replayed concurrently to multiple redirected devices you must blkparse your
trace into separate traces and replay them with independent fio invocations.
Unfortunately this also breaks the strict time ordering between multiple device
accesses.
replay_align=int
Force alignment of the byte offsets in a trace to this value. The value must be a
power of 2.
replay_scale=int
Scale bye offsets down by this factor when replaying traces. Should most likely use
replay_align as well.
Threads, processes and job synchronization
replay_skip=str
Sometimes it's useful to skip certain IO types in a replay trace. This could be,
for instance, eliminating the writes in the trace. Or not replaying the
trims/discards, if you are redirecting to a device that doesn't support them. This
option takes a comma separated list of read, write, trim, sync.
thread Fio defaults to creating jobs by using fork, however if this option is given, fio
will create jobs by using POSIX Threads' function pthread_create(3) to create
threads instead.
wait_for=str
If set, the current job won't be started until all workers of the specified waitee
job are done. wait_for operates on the job name basis, so there are a few
limitations. First, the waitee must be defined prior to the waiter job (meaning no
forward references). Second, if a job is being referenced as a waitee, it must have
a unique name (no duplicate waitees).
nice=int
Run the job with the given nice value. See man nice(2). On Windows, values less
than -15 set the process class to "High"; -1 through -15 set "Above Normal"; 1
through 15 "Below Normal"; and above 15 "Idle" priority class.
prio=int
Set the I/O priority value of this job. Linux limits us to a positive value between
0 and 7, with 0 being the highest. See man ionice(1). Refer to an appropriate
manpage for other operating systems since meaning of priority may differ. For per-
command priority setting, see the I/O engine specific `cmdprio_percentage` and
`cmdprio` options.
prioclass=int
Set the I/O priority class. See man ionice(1). For per-command priority setting,
see the I/O engine specific `cmdprio_percentage` and `cmdprio_class` options.
cpus_allowed=str
Controls the same options as cpumask, but accepts a textual specification of the
permitted CPUs instead and CPUs are indexed from 0. So to use CPUs 0 and 5 you
would specify `cpus_allowed=0,5'. This option also allows a range of CPUs to be
specified -- say you wanted a binding to CPUs 0, 5, and 8 to 15, you would set
`cpus_allowed=0,5,8-15'.
On Windows, when `cpus_allowed' is unset only CPUs from fio's current processor
group will be used and affinity settings are inherited from the system. An fio
build configured to target Windows 7 makes options that set CPUs processor group
aware and values will set both the processor group and a CPU from within that
group. For example, on a system where processor group 0 has 40 CPUs and processor
group 1 has 32 CPUs, `cpus_allowed' values between 0 and 39 will bind CPUs from
processor group 0 and `cpus_allowed' values between 40 and 71 will bind CPUs from
processor group 1. When using `cpus_allowed_policy=shared' all CPUs specified by a
single `cpus_allowed' option must be from the same processor group. For Windows fio
builds not built for Windows 7, CPUs will only be selected from (and be relative
to) whatever processor group fio happens to be running in and CPUs from other
processor groups cannot be used.
cpus_allowed_policy=str
Set the policy of how fio distributes the CPUs specified by cpus_allowed or
cpumask. Two policies are supported:
shared All jobs will share the CPU set specified.
split Each job will get a unique CPU from the CPU set.
shared is the default behavior, if the option isn't specified. If split is
specified, then fio will assign one cpu per job. If not enough CPUs are given for
the jobs listed, then fio will roundrobin the CPUs in the set.
cpumask=int
Set the CPU affinity of this job. The parameter given is a bit mask of allowed CPUs
the job may run on. So if you want the allowed CPUs to be 1 and 5, you would pass
the decimal value of (1 << 1 | 1 << 5), or 34. See man sched_setaffinity(2). This
may not work on all supported operating systems or kernel versions. This option
doesn't work well for a higher CPU count than what you can store in an integer
mask, so it can only control cpus 1-32. For boxes with larger CPU counts, use
cpus_allowed.
numa_cpu_nodes=str
Set this job running on specified NUMA nodes' CPUs. The arguments allow comma
delimited list of cpu numbers, A-B ranges, or `all'. Note, to enable NUMA options
support, fio must be built on a system with libnuma-dev(el) installed.
numa_mem_policy=str
Set this job's memory policy and corresponding NUMA nodes. Format of the arguments:
<mode>[:<nodelist>]
`mode' is one of the following memory policies: `default', `prefer', `bind',
`interleave' or `local'. For `default' and `local' memory policies, no node needs
to be specified. For `prefer', only one node is allowed. For `bind' and
`interleave' the `nodelist' may be as follows: a comma delimited list of numbers,
A-B ranges, or `all'.
cgroup=str
Add job to this control group. If it doesn't exist, it will be created. The system
must have a mounted cgroup blkio mount point for this to work. If your system
doesn't have it mounted, you can do so with:
# mount -t cgroup -o blkio none /cgroup
cgroup_weight=int
Set the weight of the cgroup to this value. See the documentation that comes with
the kernel, allowed values are in the range of 100..1000.
cgroup_nodelete=bool
Normally fio will delete the cgroups it has created after the job completion. To
override this behavior and to leave cgroups around after the job completion, set
`cgroup_nodelete=1'. This can be useful if one wants to inspect various cgroup
files after job completion. Default: false.
flow_id=int
The ID of the flow. If not specified, it defaults to being a global flow. See flow.
flow=int
Weight in token-based flow control. If this value is used, then fio regulates the
activity between two or more jobs sharing the same flow_id. Fio attempts to keep
each job activity proportional to other jobs' activities in the same flow_id group,
with respect to requested weight per job. That is, if one job has `flow=3',
another job has `flow=2' and another with `flow=1`, then there will be a roughly
3:2:1 ratio in how much one runs vs the others.
flow_sleep=int
The period of time, in microseconds, to wait after the flow counter has exceeded
its proportion before retrying operations.
stonewall, wait_for_previous
Wait for preceding jobs in the job file to exit, before starting this one. Can be
used to insert serialization points in the job file. A stone wall also implies
starting a new reporting group, see group_reporting. Optionally you can use
`stonewall=0` to disable or `stonewall=1` to enable it.
exitall
By default, fio will continue running all other jobs when one job finishes.
Sometimes this is not the desired action. Setting exitall will instead make fio
terminate all jobs in the same group, as soon as one job of that group finishes.
exit_what=str
By default, fio will continue running all other jobs when one job finishes.
Sometimes this is not the desired action. Setting exitall will instead make fio
terminate all jobs in the same group. The option exit_what allows you to control
which jobs get terminated when exitall is enabled. The default value is group.
The allowed values are:
all terminates all jobs.
group is the default and does not change the behaviour of exitall.
stonewall
terminates all currently running jobs across all groups and continues
execution with the next stonewalled group.
exec_prerun=str
Before running this job, issue the command specified through system(3). Output is
redirected in a file called `jobname.prerun.txt'.
exec_postrun=str
After the job completes, issue the command specified though system(3). Output is
redirected in a file called `jobname.postrun.txt'.
uid=int
Instead of running as the invoking user, set the user ID to this value before the
thread/process does any work.
gid=int
Set group ID, see uid.
Verification
verify_only
Do not perform specified workload, only verify data still matches previous
invocation of this workload. This option allows one to check data multiple times at
a later date without overwriting it. This option makes sense only for workloads
that write data, and does not support workloads with the time_based option set.
do_verify=bool
Run the verify phase after a write phase. Only valid if verify is set. Default:
true.
verify=str
If writing to a file, fio can verify the file contents after each iteration of the
job. Each verification method also implies verification of special header, which is
written to the beginning of each block. This header also includes meta information,
like offset of the block, block number, timestamp when block was written, etc.
verify can be combined with verify_pattern option. The allowed values are:
md5 Use an md5 sum of the data area and store it in the header of each
block.
crc64 Use an experimental crc64 sum of the data area and store it in the
header of each block.
crc32c Use a crc32c sum of the data area and store it in the header of each
block. This will automatically use hardware acceleration (e.g. SSE4.2
on an x86 or CRC crypto extensions on ARM64) but will fall back to
software crc32c if none is found. Generally the fastest checksum fio
supports when hardware accelerated.
crc32c-intel
Synonym for crc32c.
crc32 Use a crc32 sum of the data area and store it in the header of each
block.
crc16 Use a crc16 sum of the data area and store it in the header of each
block.
crc7 Use a crc7 sum of the data area and store it in the header of each
block.
xxhash Use xxhash as the checksum function. Generally the fastest software
checksum that fio supports.
sha512 Use sha512 as the checksum function.
sha256 Use sha256 as the checksum function.
sha1 Use optimized sha1 as the checksum function.
sha3-224
Use optimized sha3-224 as the checksum function.
sha3-256
Use optimized sha3-256 as the checksum function.
sha3-384
Use optimized sha3-384 as the checksum function.
sha3-512
Use optimized sha3-512 as the checksum function.
meta This option is deprecated, since now meta information is included in
generic verification header and meta verification happens by default.
For detailed information see the description of the verify setting.
This option is kept because of compatibility's sake with old
configurations. Do not use it.
pattern
Verify a strict pattern. Normally fio includes a header with some
basic information and checksumming, but if this option is set, only
the specific pattern set with verify_pattern is verified.
null Only pretend to verify. Useful for testing internals with
`ioengine=null', not for much else.
This option can be used for repeated burn-in tests of a system to make sure that
the written data is also correctly read back. If the data direction given is a read
or random read, fio will assume that it should verify a previously written file. If
the data direction includes any form of write, the verify will be of the newly
written data.
To avoid false verification errors, do not use the norandommap option when
verifying data with async I/O engines and I/O depths > 1. Or use the norandommap
and the lfsr random generator together to avoid writing to the same offset with
multiple outstanding I/Os.
verify_offset=int
Swap the verification header with data somewhere else in the block before writing.
It is swapped back before verifying.
verify_interval=int
Write the verification header at a finer granularity than the blocksize. It will be
written for chunks the size of verify_interval. blocksize should divide this
evenly.
verify_pattern=str
If set, fio will fill the I/O buffers with this pattern. Fio defaults to filling
with totally random bytes, but sometimes it's interesting to fill with a known
pattern for I/O verification purposes. Depending on the width of the pattern, fio
will fill 1/2/3/4 bytes of the buffer at the time (it can be either a decimal or a
hex number). The verify_pattern if larger than a 32-bit quantity has to be a hex
number that starts with either "0x" or "0X". Use with verify. Also, verify_pattern
supports %o format, which means that for each block offset will be written and then
verified back, e.g.:
verify_pattern=%o
Or use combination of everything:
verify_pattern=0xff%o"abcd"-12
verify_fatal=bool
Normally fio will keep checking the entire contents before quitting on a block
verification failure. If this option is set, fio will exit the job on the first
observed failure. Default: false.
verify_dump=bool
If set, dump the contents of both the original data block and the data block we
read off disk to files. This allows later analysis to inspect just what kind of
data corruption occurred. Off by default.
verify_async=int
Fio will normally verify I/O inline from the submitting thread. This option takes
an integer describing how many async offload threads to create for I/O verification
instead, causing fio to offload the duty of verifying I/O contents to one or more
separate threads. If using this offload option, even sync I/O engines can benefit
from using an iodepth setting higher than 1, as it allows them to have I/O in
flight while verifies are running. Defaults to 0 async threads, i.e. verification
is not asynchronous.
verify_async_cpus=str
Tell fio to set the given CPU affinity on the async I/O verification threads. See
cpus_allowed for the format used.
verify_backlog=int
Fio will normally verify the written contents of a job that utilizes verify once
that job has completed. In other words, everything is written then everything is
read back and verified. You may want to verify continually instead for a variety of
reasons. Fio stores the meta data associated with an I/O block in memory, so for
large verify workloads, quite a bit of memory would be used up holding this meta
data. If this option is enabled, fio will write only N blocks before verifying
these blocks.
verify_backlog_batch=int
Control how many blocks fio will verify if verify_backlog is set. If not set, will
default to the value of verify_backlog (meaning the entire queue is read back and
verified). If verify_backlog_batch is less than verify_backlog then not all blocks
will be verified, if verify_backlog_batch is larger than verify_backlog, some
blocks will be verified more than once.
verify_state_save=bool
When a job exits during the write phase of a verify workload, save its current
state. This allows fio to replay up until that point, if the verify state is loaded
for the verify read phase. The format of the filename is, roughly:
<type>-<jobname>-<jobindex>-verify.state.
<type> is "local" for a local run, "sock" for a client/server socket connection,
and "ip" (192.168.0.1, for instance) for a networked client/server connection.
Defaults to true.
verify_state_load=bool
If a verify termination trigger was used, fio stores the current write state of
each thread. This can be used at verification time so that fio knows how far it
should verify. Without this information, fio will run a full verification pass,
according to the settings in the job file used. Default false.
trim_percentage=int
Number of verify blocks to discard/trim.
trim_verify_zero=bool
Verify that trim/discarded blocks are returned as zeros.
trim_backlog=int
Verify that trim/discarded blocks are returned as zeros.
trim_backlog_batch=int
Trim this number of I/O blocks.
experimental_verify=bool
Enable experimental verification.
Steady state
steadystate=str:float, ss=str:float
Define the criterion and limit for assessing steady state performance. The first
parameter designates the criterion whereas the second parameter sets the threshold.
When the criterion falls below the threshold for the specified duration, the job
will stop. For example, `iops_slope:0.1%' will direct fio to terminate the job when
the least squares regression slope falls below 0.1% of the mean IOPS. If
group_reporting is enabled this will apply to all jobs in the group. Below is the
list of available steady state assessment criteria. All assessments are carried out
using only data from the rolling collection window. Threshold limits can be
expressed as a fixed value or as a percentage of the mean in the collection window.
When using this feature, most jobs should include the time_based and runtime
options or the loops option so that fio does not stop running after it has covered
the full size of the specified file(s) or device(s).
iops Collect IOPS data. Stop the job if all individual IOPS
measurements are within the specified limit of the mean IOPS
(e.g., `iops:2' means that all individual IOPS values must be
within 2 of the mean, whereas `iops:0.2%' means that all
individual IOPS values must be within 0.2% of the mean IOPS to
terminate the job).
iops_slope
Collect IOPS data and calculate the least squares regression
slope. Stop the job if the slope falls below the specified
limit.
bw Collect bandwidth data. Stop the job if all individual
bandwidth measurements are within the specified limit of the
mean bandwidth.
bw_slope
Collect bandwidth data and calculate the least squares
regression slope. Stop the job if the slope falls below the
specified limit.
steadystate_duration=time, ss_dur=time
A rolling window of this duration will be used to judge whether steady state
has been reached. Data will be collected once per second. The default is 0
which disables steady state detection. When the unit is omitted, the value
is interpreted in seconds.
steadystate_ramp_time=time, ss_ramp=time
Allow the job to run for the specified duration before beginning data
collection for checking the steady state job termination criterion. The
default is 0. When the unit is omitted, the value is interpreted in seconds.
Measurements and reporting
per_job_logs=bool
If set, this generates bw/clat/iops log with per file private filenames. If not
set, jobs with identical names will share the log filename. Default: true.
group_reporting
It may sometimes be interesting to display statistics for groups of jobs as a whole
instead of for each individual job. This is especially true if numjobs is used;
looking at individual thread/process output quickly becomes unwieldy. To see the
final report per-group instead of per-job, use group_reporting. Jobs in a file will
be part of the same reporting group, unless if separated by a stonewall, or by
using new_group.
new_group
Start a new reporting group. See: group_reporting. If not given, all jobs in a file
will be part of the same reporting group, unless separated by a stonewall.
stats=bool
By default, fio collects and shows final output results for all jobs that run. If
this option is set to 0, then fio will ignore it in the final stat output.
write_bw_log=str
If given, write a bandwidth log for this job. Can be used to store data of the
bandwidth of the jobs in their lifetime.
If no str argument is given, the default filename of `jobname_type.x.log' is used.
Even when the argument is given, fio will still append the type of log. So if one
specifies:
write_bw_log=foo
The actual log name will be `foo_bw.x.log' where `x' is the index of the job (1..N,
where N is the number of jobs). If per_job_logs is false, then the filename will
not include the `.x` job index.
The included fio_generate_plots script uses gnuplot to turn these text files into
nice graphs. See the LOG FILE FORMATS section for how data is structured within the
file.
write_lat_log=str
Same as write_bw_log, except this option creates I/O submission (e.g.,
`name_slat.x.log'), completion (e.g., `name_clat.x.log'), and total (e.g.,
`name_lat.x.log') latency files instead. See write_bw_log for details about the
filename format and the LOG FILE FORMATS section for how data is structured within
the files.
write_hist_log=str
Same as write_bw_log but writes an I/O completion latency histogram file (e.g.,
`name_hist.x.log') instead. Note that this file will be empty unless log_hist_msec
has also been set. See write_bw_log for details about the filename format and the
LOG FILE FORMATS section for how data is structured within the file.
write_iops_log=str
Same as write_bw_log, but writes an IOPS file (e.g. `name_iops.x.log`) instead.
Because fio defaults to individual I/O logging, the value entry in the IOPS log
will be 1 unless windowed logging (see log_avg_msec) has been enabled. See
write_bw_log for details about the filename format and LOG FILE FORMATS for how
data is structured within the file.
log_entries=int
By default, fio will log an entry in the iops, latency, or bw log for every I/O
that completes. The initial number of I/O log entries is 1024. When the log
entries are all used, new log entries are dynamically allocated. This dynamic log
entry allocation may negatively impact time-related statistics such as I/O tail
latencies (e.g. 99.9th percentile completion latency). This option allows
specifying a larger initial number of log entries to avoid run-time allocation of
new log entries, resulting in more precise time-related I/O statistics. Also see
log_avg_msec as well. Defaults to 1024.
log_avg_msec=int
By default, fio will log an entry in the iops, latency, or bw log for every I/O
that completes. When writing to the disk log, that can quickly grow to a very large
size. Setting this option makes fio average the each log entry over the specified
period of time, reducing the resolution of the log. See log_max_value as well.
Defaults to 0, logging all entries. Also see LOG FILE FORMATS section.
log_hist_msec=int
Same as log_avg_msec, but logs entries for completion latency histograms. Computing
latency percentiles from averages of intervals using log_avg_msec is inaccurate.
Setting this option makes fio log histogram entries over the specified period of
time, reducing log sizes for high IOPS devices while retaining percentile accuracy.
See log_hist_coarseness and write_hist_log as well. Defaults to 0, meaning
histogram logging is disabled.
log_hist_coarseness=int
Integer ranging from 0 to 6, defining the coarseness of the resolution of the
histogram logs enabled with log_hist_msec. For each increment in coarseness, fio
outputs half as many bins. Defaults to 0, for which histogram logs contain 1216
latency bins. See LOG FILE FORMATS section.
log_max_value=bool
If log_avg_msec is set, fio logs the average over that window. If you instead want
to log the maximum value, set this option to 1. Defaults to 0, meaning that
averaged values are logged.
log_offset=bool
If this is set, the iolog options will include the byte offset for the I/O entry as
well as the other data values. Defaults to 0 meaning that offsets are not present
in logs. Also see LOG FILE FORMATS section.
log_prio=bool
If this is set, the iolog options will include the I/O priority for the I/O entry
as well as the other data values. Defaults to 0 meaning that I/O priorities are not
present in logs. Also see LOG FILE FORMATS section.
log_compression=int
If this is set, fio will compress the I/O logs as it goes, to keep the memory
footprint lower. When a log reaches the specified size, that chunk is removed and
compressed in the background. Given that I/O logs are fairly highly compressible,
this yields a nice memory savings for longer runs. The downside is that the
compression will consume some background CPU cycles, so it may impact the run.
This, however, is also true if the logging ends up consuming most of the system
memory. So pick your poison. The I/O logs are saved normally at the end of a run,
by decompressing the chunks and storing them in the specified log file. This
feature depends on the availability of zlib.
log_compression_cpus=str
Define the set of CPUs that are allowed to handle online log compression for the
I/O jobs. This can provide better isolation between performance sensitive jobs, and
background compression work. See cpus_allowed for the format used.
log_store_compressed=bool
If set, fio will store the log files in a compressed format. They can be
decompressed with fio, using the --inflate-log command line parameter. The files
will be stored with a `.fz' suffix.
log_unix_epoch=bool
If set, fio will log Unix timestamps to the log files produced by enabling
write_type_log for each log type, instead of the default zero-based timestamps.
log_alternate_epoch=bool
If set, fio will log timestamps based on the epoch used by the clock specified in
the log_alternate_epoch_clock_id option, to the log files produced by enabling
write_type_log for each log type, instead of the default zero-based timestamps.
log_alternate_epoch_clock_id=int
Specifies the clock_id to be used by clock_gettime to obtain the alternate epoch if
either Blog_unix_epoch or log_alternate_epoch are true. Otherwise has no effect.
Default value is 0, or CLOCK_REALTIME.
block_error_percentiles=bool
If set, record errors in trim block-sized units from writes and trims and output a
histogram of how many trims it took to get to errors, and what kind of error was
encountered.
bwavgtime=int
Average the calculated bandwidth over the given time. Value is specified in
milliseconds. If the job also does bandwidth logging through write_bw_log, then the
minimum of this option and log_avg_msec will be used. Default: 500ms.
iopsavgtime=int
Average the calculated IOPS over the given time. Value is specified in
milliseconds. If the job also does IOPS logging through write_iops_log, then the
minimum of this option and log_avg_msec will be used. Default: 500ms.
disk_util=bool
Generate disk utilization statistics, if the platform supports it. Default: true.
disable_lat=bool
Disable measurements of total latency numbers. Useful only for cutting back the
number of calls to gettimeofday(2), as that does impact performance at really high
IOPS rates. Note that to really get rid of a large amount of these calls, this
option must be used with disable_slat and disable_bw_measurement as well.
disable_clat=bool
Disable measurements of completion latency numbers. See disable_lat.
disable_slat=bool
Disable measurements of submission latency numbers. See disable_lat.
disable_bw_measurement=bool, disable_bw=bool
Disable measurements of throughput/bandwidth numbers. See disable_lat.
slat_percentiles=bool
Report submission latency percentiles. Submission latency is not recorded for
synchronous ioengines.
clat_percentiles=bool
Report completion latency percentiles.
lat_percentiles=bool
Report total latency percentiles. Total latency is the sum of submission latency
and completion latency.
percentile_list=float_list
Overwrite the default list of percentiles for latencies and the block error
histogram. Each number is a floating point number in the range (0,100], and the
maximum length of the list is 20. Use ':' to separate the numbers. For example,
`--percentile_list=99.5:99.9' will cause fio to report the latency durations below
which 99.5% and 99.9% of the observed latencies fell, respectively.
significant_figures=int
If using --output-format of `normal', set the significant figures to this value.
Higher values will yield more precise IOPS and throughput units, while lower values
will round. Requires a minimum value of 1 and a maximum value of 10. Defaults to 4.
Error handling
exitall_on_error
When one job finishes in error, terminate the rest. The default is to wait for each
job to finish.
continue_on_error=str
Normally fio will exit the job on the first observed failure. If this option is
set, fio will continue the job when there is a 'non-fatal error' (EIO or EILSEQ)
until the runtime is exceeded or the I/O size specified is completed. If this
option is used, there are two more stats that are appended, the total error count
and the first error. The error field given in the stats is the first error that was
hit during the run. The allowed values are:
none Exit on any I/O or verify errors.
read Continue on read errors, exit on all others.
write Continue on write errors, exit on all others.
io Continue on any I/O error, exit on all others.
verify Continue on verify errors, exit on all others.
all Continue on all errors.
0 Backward-compatible alias for 'none'.
1 Backward-compatible alias for 'all'.
ignore_error=str
Sometimes you want to ignore some errors during test in that case you can specify
error list for each error type, instead of only being able to ignore the default
'non-fatal error' using continue_on_error.
`ignore_error=READ_ERR_LIST,WRITE_ERR_LIST,VERIFY_ERR_LIST' errors for given error
type is separated with ':'. Error may be symbol ('ENOSPC', 'ENOMEM') or integer.
Example:
ignore_error=EAGAIN,ENOSPC:122
This option will ignore EAGAIN from READ, and ENOSPC and 122(EDQUOT) from WRITE.
This option works by overriding continue_on_error with the list of errors for each
error type if any.
error_dump=bool
If set dump every error even if it is non fatal, true by default. If disabled only
fatal error will be dumped.
Running predefined workloads
Fio includes predefined profiles that mimic the I/O workloads generated by other tools.
profile=str
The predefined workload to run. Current profiles are:
tiobench
Threaded I/O bench (tiotest/tiobench) like workload.
act Aerospike Certification Tool (ACT) like workload.
To view a profile's additional options use --cmdhelp after specifying the profile. For
example:
$ fio --profile=act --cmdhelp
Act profile options
device-names=str
Devices to use.
load=int
ACT load multiplier. Default: 1.
test-duration=time
How long the entire test takes to run. When the unit is omitted, the value is given
in seconds. Default: 24h.
threads-per-queue=int
Number of read I/O threads per device. Default: 8.
read-req-num-512-blocks=int
Number of 512B blocks to read at the time. Default: 3.
large-block-op-kbytes=int
Size of large block ops in KiB (writes). Default: 131072.
prep Set to run ACT prep phase.
Tiobench profile options
size=str
Size in MiB.
block=int
Block size in bytes. Default: 4096.
numruns=int
Number of runs.
dir=str
Test directory.
threads=int
Number of threads.
OUTPUT
Fio spits out a lot of output. While running, fio will display the status of the jobs
created. An example of that would be:
Jobs: 1 (f=1): [_(1),M(1)][24.8%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 01m:31s]
The characters inside the first set of square brackets denote the current status of each
thread. The first character is the first job defined in the job file, and so forth. The
possible values (in typical life cycle order) are:
P Thread setup, but not started.
C Thread created.
I Thread initialized, waiting or generating necessary data.
p Thread running pre-reading file(s).
/ Thread is in ramp period.
R Running, doing sequential reads.
r Running, doing random reads.
W Running, doing sequential writes.
w Running, doing random writes.
M Running, doing mixed sequential reads/writes.
m Running, doing mixed random reads/writes.
D Running, doing sequential trims.
d Running, doing random trims.
F Running, currently waiting for fsync(2).
V Running, doing verification of written data.
f Thread finishing.
E Thread exited, not reaped by main thread yet.
- Thread reaped.
X Thread reaped, exited with an error.
K Thread reaped, exited due to signal.
Fio will condense the thread string as not to take up more space on the command line than
needed. For instance, if you have 10 readers and 10 writers running, the output would look
like this:
Jobs: 20 (f=20): [R(10),W(10)][4.0%][r=20.5MiB/s,w=23.5MiB/s][r=82,w=94 IOPS][eta 57m:36s]
Note that the status string is displayed in order, so it's possible to tell which of the
jobs are currently doing what. In the example above this means that jobs 1--10 are readers
and 11--20 are writers.
The other values are fairly self explanatory -- number of threads currently running and
doing I/O, the number of currently open files (f=), the estimated completion percentage,
the rate of I/O since last check (read speed listed first, then write speed and optionally
trim speed) in terms of bandwidth and IOPS, and time to completion for the current running
group. It's impossible to estimate runtime of the following groups (if any).
When fio is done (or interrupted by Ctrl-C), it will show the data for each thread, group
of threads, and disks in that order. For each overall thread (or group) the output looks
like:
Client1: (groupid=0, jobs=1): err= 0: pid=16109: Sat Jun 24 12:07:54 2017
write: IOPS=88, BW=623KiB/s (638kB/s)(30.4MiB/50032msec)
slat (nsec): min=500, max=145500, avg=8318.00, stdev=4781.50
clat (usec): min=170, max=78367, avg=4019.02, stdev=8293.31
lat (usec): min=174, max=78375, avg=4027.34, stdev=8291.79
clat percentiles (usec):
| 1.00th=[ 302], 5.00th=[ 326], 10.00th=[ 343], 20.00th=[ 363],
| 30.00th=[ 392], 40.00th=[ 404], 50.00th=[ 416], 60.00th=[ 445],
| 70.00th=[ 816], 80.00th=[ 6718], 90.00th=[12911], 95.00th=[21627],
| 99.00th=[43779], 99.50th=[51643], 99.90th=[68682], 99.95th=[72877],
| 99.99th=[78119]
bw ( KiB/s): min= 532, max= 686, per=0.10%, avg=622.87, stdev=24.82, samples= 100
iops : min= 76, max= 98, avg=88.98, stdev= 3.54, samples= 100
lat (usec) : 250=0.04%, 500=64.11%, 750=4.81%, 1000=2.79%
lat (msec) : 2=4.16%, 4=1.84%, 10=4.90%, 20=11.33%, 50=5.37%
lat (msec) : 100=0.65%
cpu : usr=0.27%, sys=0.18%, ctx=12072, majf=0, minf=21
IO depths : 1=85.0%, 2=13.1%, 4=1.8%, 8=0.1%, 16=0.0%, 32=0.0%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
issued rwt: total=0,4450,0, short=0,0,0, dropped=0,0,0
latency : target=0, window=0, percentile=100.00%, depth=8
The job name (or first job's name when using group_reporting) is printed, along with the
group id, count of jobs being aggregated, last error id seen (which is 0 when there are no
errors), pid/tid of that thread and the time the job/group completed. Below are the I/O
statistics for each data direction performed (showing writes in the example above). In the
order listed, they denote:
read/write/trim
The string before the colon shows the I/O direction the statistics are for.
IOPS is the average I/Os performed per second. BW is the average bandwidth
rate shown as: value in power of 2 format (value in power of 10 format). The
last two values show: (total I/O performed in power of 2 format / runtime of
that thread).
slat Submission latency (min being the minimum, max being the maximum, avg being
the average, stdev being the standard deviation). This is the time it took
to submit the I/O. For sync I/O this row is not displayed as the slat is
really the completion latency (since queue/complete is one operation there).
This value can be in nanoseconds, microseconds or milliseconds --- fio will
choose the most appropriate base and print that (in the example above
nanoseconds was the best scale). Note: in --minimal mode latencies are
always expressed in microseconds.
clat Completion latency. Same names as slat, this denotes the time from
submission to completion of the I/O pieces. For sync I/O, clat will usually
be equal (or very close) to 0, as the time from submit to complete is
basically just CPU time (I/O has already been done, see slat explanation).
lat Total latency. Same names as slat and clat, this denotes the time from when
fio created the I/O unit to completion of the I/O operation.
bw Bandwidth statistics based on samples. Same names as the xlat stats, but
also includes the number of samples taken (samples) and an approximate
percentage of total aggregate bandwidth this thread received in its group
(per). This last value is only really useful if the threads in this group
are on the same disk, since they are then competing for disk access.
iops IOPS statistics based on samples. Same names as bw.
lat (nsec/usec/msec)
The distribution of I/O completion latencies. This is the time from when I/O
leaves fio and when it gets completed. Unlike the separate read/write/trim
sections above, the data here and in the remaining sections apply to all
I/Os for the reporting group. 250=0.04% means that 0.04% of the I/Os
completed in under 250us. 500=64.11% means that 64.11% of the I/Os required
250 to 499us for completion.
cpu CPU usage. User and system time, along with the number of context switches
this thread went through, usage of system and user time, and finally the
number of major and minor page faults. The CPU utilization numbers are
averages for the jobs in that reporting group, while the context and fault
counters are summed.
IO depths
The distribution of I/O depths over the job lifetime. The numbers are
divided into powers of 2 and each entry covers depths from that value up to
those that are lower than the next entry -- e.g., 16= covers depths from 16
to 31. Note that the range covered by a depth distribution entry can be
different to the range covered by the equivalent submit/complete
distribution entry.
IO submit
How many pieces of I/O were submitting in a single submit call. Each entry
denotes that amount and below, until the previous entry -- e.g., 16=100%
means that we submitted anywhere between 9 to 16 I/Os per submit call. Note
that the range covered by a submit distribution entry can be different to
the range covered by the equivalent depth distribution entry.
IO complete
Like the above submit number, but for completions instead.
IO issued rwt
The number of read/write/trim requests issued, and how many of them were
short or dropped.
IO latency
These values are for latency_target and related options. When these options
are engaged, this section describes the I/O depth required to meet the
specified latency target.
After each client has been listed, the group statistics are printed. They will look like
this:
Run status group 0 (all jobs):
READ: bw=20.9MiB/s (21.9MB/s), 10.4MiB/s-10.8MiB/s (10.9MB/s-11.3MB/s), io=64.0MiB (67.1MB), run=2973-3069msec
WRITE: bw=1231KiB/s (1261kB/s), 616KiB/s-621KiB/s (630kB/s-636kB/s), io=64.0MiB (67.1MB), run=52747-53223msec
For each data direction it prints:
bw Aggregate bandwidth of threads in this group followed by the minimum and
maximum bandwidth of all the threads in this group. Values outside of
brackets are power-of-2 format and those within are the equivalent value in
a power-of-10 format.
io Aggregate I/O performed of all threads in this group. The format is the same
as bw.
run The smallest and longest runtimes of the threads in this group.
And finally, the disk statistics are printed. This is Linux specific. They will look like
this:
Disk stats (read/write):
sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00%
Each value is printed for both reads and writes, with reads first. The numbers denote:
ios Number of I/Os performed by all groups.
merge Number of merges performed by the I/O scheduler.
ticks Number of ticks we kept the disk busy.
in_queue
Total time spent in the disk queue.
util The disk utilization. A value of 100% means we kept the disk busy
constantly, 50% would be a disk idling half of the time.
It is also possible to get fio to dump the current output while it is running, without
terminating the job. To do that, send fio the USR1 signal. You can also get regularly
timed dumps by using the --status-interval parameter, or by creating a file in `/tmp'
named `fio-dump-status'. If fio sees this file, it will unlink it and dump the current
output status.
TERSE OUTPUT
For scripted usage where you typically want to generate tables or graphs of the results,
fio can output the results in a semicolon separated format. The format is one long line of
values, such as:
2;card0;0;0;7139336;121836;60004;1;10109;27.932460;116.933948;220;126861;3495.446807;1085.368601;226;126864;3523.635629;1089.012448;24063;99944;50.275485%;59818.274627;5540.657370;7155060;122104;60004;1;8338;29.086342;117.839068;388;128077;5032.488518;1234.785715;391;128085;5061.839412;1236.909129;23436;100928;50.287926%;59964.832030;5644.844189;14.595833%;19.394167%;123706;0;7313;0.1%;0.1%;0.1%;0.1%;0.1%;0.1%;100.0%;0.00%;0.00%;0.00%;0.00%;0.00%;0.00%;0.01%;0.02%;0.05%;0.16%;6.04%;40.40%;52.68%;0.64%;0.01%;0.00%;0.01%;0.00%;0.00%;0.00%;0.00%;0.00%
A description of this job goes here.
The job description (if provided) follows on a second line for terse v2. It appears on
the same line for other terse versions.
To enable terse output, use the --minimal or `--output-format=terse' command line options.
The first value is the version of the terse output format. If the output has to be changed
for some reason, this number will be incremented by 1 to signify that change.
Split up, the format is as follows (comments in brackets denote when a field was
introduced or whether it's specific to some terse version):
terse version, fio version [v3], jobname, groupid, error
READ status:
Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
Submission latency: min, max, mean, stdev (usec)
Completion latency: min, max, mean, stdev (usec)
Completion latency percentiles: 20 fields (see below)
Total latency: min, max, mean, stdev (usec)
Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
IOPS [v5]: min, max, mean, stdev, number of samples
WRITE status:
Total IO (KiB), bandwidth (KiB/sec), IOPS, runtime (msec)
Submission latency: min, max, mean, stdev (usec)
Completion latency: min, max, mean, stdev (usec)
Completion latency percentiles: 20 fields (see below)
Total latency: min, max, mean, stdev (usec)
Bw (KiB/s): min, max, aggregate percentage of total, mean, stdev, number of samples [v5]
IOPS [v5]: min, max, mean, stdev, number of samples
TRIM status [all but version 3]:
Fields are similar to READ/WRITE status.
CPU usage:
user, system, context switches, major faults, minor faults
I/O depths:
<=1, 2, 4, 8, 16, 32, >=64
I/O latencies microseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000
I/O latencies milliseconds:
<=2, 4, 10, 20, 50, 100, 250, 500, 750, 1000, 2000, >=2000
Disk utilization [v3]:
disk name, read ios, write ios, read merges, write merges, read ticks, write ticks, time spent in queue, disk utilization percentage
Additional Info (dependent on continue_on_error, default off):
total # errors, first error code
Additional Info (dependent on description being set):
Text description
Completion latency percentiles can be a grouping of up to 20 sets, so for the terse output
fio writes all of them. Each field will look like this:
1.00%=6112
which is the Xth percentile, and the `usec' latency associated with it.
For Disk utilization, all disks used by fio are shown. So for each disk there will be a
disk utilization section.
Below is a single line containing short names for each of the fields in the minimal output
v3, separated by semicolons:
terse_version_3;fio_version;jobname;groupid;error;read_kb;read_bandwidth_kb;read_iops;read_runtime_ms;read_slat_min_us;read_slat_max_us;read_slat_mean_us;read_slat_dev_us;read_clat_min_us;read_clat_max_us;read_clat_mean_us;read_clat_dev_us;read_clat_pct01;read_clat_pct02;read_clat_pct03;read_clat_pct04;read_clat_pct05;read_clat_pct06;read_clat_pct07;read_clat_pct08;read_clat_pct09;read_clat_pct10;read_clat_pct11;read_clat_pct12;read_clat_pct13;read_clat_pct14;read_clat_pct15;read_clat_pct16;read_clat_pct17;read_clat_pct18;read_clat_pct19;read_clat_pct20;read_tlat_min_us;read_lat_max_us;read_lat_mean_us;read_lat_dev_us;read_bw_min_kb;read_bw_max_kb;read_bw_agg_pct;read_bw_mean_kb;read_bw_dev_kb;write_kb;write_bandwidth_kb;write_iops;write_runtime_ms;write_slat_min_us;write_slat_max_us;write_slat_mean_us;write_slat_dev_us;write_clat_min_us;write_clat_max_us;write_clat_mean_us;write_clat_dev_us;write_clat_pct01;write_clat_pct02;write_clat_pct03;write_clat_pct04;write_clat_pct05;write_clat_pct06;write_clat_pct07;write_clat_pct08;write_clat_pct09;write_clat_pct10;write_clat_pct11;write_clat_pct12;write_clat_pct13;write_clat_pct14;write_clat_pct15;write_clat_pct16;write_clat_pct17;write_clat_pct18;write_clat_pct19;write_clat_pct20;write_tlat_min_us;write_lat_max_us;write_lat_mean_us;write_lat_dev_us;write_bw_min_kb;write_bw_max_kb;write_bw_agg_pct;write_bw_mean_kb;write_bw_dev_kb;cpu_user;cpu_sys;cpu_csw;cpu_mjf;cpu_minf;iodepth_1;iodepth_2;iodepth_4;iodepth_8;iodepth_16;iodepth_32;iodepth_64;lat_2us;lat_4us;lat_10us;lat_20us;lat_50us;lat_100us;lat_250us;lat_500us;lat_750us;lat_1000us;lat_2ms;lat_4ms;lat_10ms;lat_20ms;lat_50ms;lat_100ms;lat_250ms;lat_500ms;lat_750ms;lat_1000ms;lat_2000ms;lat_over_2000ms;disk_name;disk_read_iops;disk_write_iops;disk_read_merges;disk_write_merges;disk_read_ticks;write_ticks;disk_queue_time;disk_util
In client/server mode terse output differs from what appears when jobs are run locally.
Disk utilization data is omitted from the standard terse output and for v3 and later
appears on its own separate line at the end of each terse reporting cycle.
JSON OUTPUT
The json output format is intended to be both human readable and convenient for automated
parsing. For the most part its sections mirror those of the normal output. The runtime
value is reported in msec and the bw value is reported in 1024 bytes per second units.
JSON+ OUTPUT
The json+ output format is identical to the json output format except that it adds a full
dump of the completion latency bins. Each bins object contains a set of (key, value) pairs
where keys are latency durations and values count how many I/Os had completion latencies
of the corresponding duration. For example, consider:
"bins" : { "87552" : 1, "89600" : 1, "94720" : 1, "96768" : 1, "97792" : 1, "99840"
: 1, "100864" : 2, "103936" : 6, "104960" : 534, "105984" : 5995, "107008" : 7529,
... }
This data indicates that one I/O required 87,552ns to complete, two I/Os required
100,864ns to complete, and 7529 I/Os required 107,008ns to complete.
Also included with fio is a Python script fio_jsonplus_clat2csv that takes json+ output
and generates CSV-formatted latency data suitable for plotting.
The latency durations actually represent the midpoints of latency intervals. For details
refer to `stat.h' in the fio source.
TRACE FILE FORMAT
There are two trace file format that you can encounter. The older (v1) format is
unsupported since version 1.20-rc3 (March 2008). It will still be described below in case
that you get an old trace and want to understand it.
In any case the trace is a simple text file with a single action per line.
Trace file format v1
Each line represents a single I/O action in the following format:
rw, offset, length
where `rw=0/1' for read/write, and the `offset' and `length' entries being in
bytes.
This format is not supported in fio versions >= 1.20-rc3.
Trace file format v2
The second version of the trace file format was added in fio version 1.17. It
allows to access more then one file per trace and has a bigger set of possible file
actions.
The first line of the trace file has to be:
"fio version 2 iolog"
Following this can be lines in two different formats, which are described below.
The file management format:
filename action
The `filename' is given as an absolute path. The `action' can be one of
these:
add Add the given `filename' to the trace.
open Open the file with the given `filename'. The `filename' has to
have been added with the add action before.
close Close the file with the given `filename'. The file has to have
been opened before.
The file I/O action format:
filename action offset length
The `filename' is given as an absolute path, and has to have been added and
opened before it can be used with this format. The `offset' and `length' are
given in bytes. The `action' can be one of these:
wait Wait for `offset' microseconds. Everything below 100 is
discarded. The time is relative to the previous `wait'
statement.
read Read `length' bytes beginning from `offset'.
write Write `length' bytes beginning from `offset'.
sync fsync(2) the file.
datasync
fdatasync(2) the file.
trim Trim the given file from the given `offset' for `length'
bytes.
I/O REPLAY - MERGING TRACES
Colocation is a common practice used to get the most out of a machine. Knowing which
workloads play nicely with each other and which ones don't is a much harder task. While
fio can replay workloads concurrently via multiple jobs, it leaves some variability up to
the scheduler making results harder to reproduce. Merging is a way to make the order of
events consistent.
Merging is integrated into I/O replay and done when a merge_blktrace_file is specified.
The list of files passed to read_iolog go through the merge process and output a single
file stored to the specified file. The output file is passed on as if it were the only
file passed to read_iolog. An example would look like:
$ fio --read_iolog="<file1>:<file2>" --merge_blktrace_file="<output_file>"
Creating only the merged file can be done by passing the command line argument merge-
blktrace-only.
Scaling traces can be done to see the relative impact of any particular trace being slowed
down or sped up. merge_blktrace_scalars takes in a colon separated list of percentage
scalars. It is index paired with the files passed to read_iolog.
With scaling, it may be desirable to match the running time of all traces. This can be
done with merge_blktrace_iters. It is index paired with read_iolog just like
merge_blktrace_scalars.
In an example, given two traces, A and B, each 60s long. If we want to see the impact of
trace A issuing IOs twice as fast and repeat trace A over the runtime of trace B, the
following can be done:
$ fio --read_iolog="<trace_a>:"<trace_b>" --merge_blktrace_file"<output_file>"
--merge_blktrace_scalars="50:100" --merge_blktrace_iters="2:1"
This runs trace A at 2x the speed twice for approximately the same runtime as a single run
of trace B.
CPU IDLENESS PROFILING
In some cases, we want to understand CPU overhead in a test. For example, we test patches
for the specific goodness of whether they reduce CPU usage. Fio implements a balloon
approach to create a thread per CPU that runs at idle priority, meaning that it only runs
when nobody else needs the cpu. By measuring the amount of work completed by the thread,
idleness of each CPU can be derived accordingly.
An unit work is defined as touching a full page of unsigned characters. Mean and standard
deviation of time to complete an unit work is reported in "unit work" section. Options can
be chosen to report detailed percpu idleness or overall system idleness by aggregating
percpu stats.
VERIFICATION AND TRIGGERS
Fio is usually run in one of two ways, when data verification is done. The first is a
normal write job of some sort with verify enabled. When the write phase has completed, fio
switches to reads and verifies everything it wrote. The second model is running just the
write phase, and then later on running the same job (but with reads instead of writes) to
repeat the same I/O patterns and verify the contents. Both of these methods depend on the
write phase being completed, as fio otherwise has no idea how much data was written.
With verification triggers, fio supports dumping the current write state to local files.
Then a subsequent read verify workload can load this state and know exactly where to stop.
This is useful for testing cases where power is cut to a server in a managed fashion, for
instance.
A verification trigger consists of two things:
1) Storing the write state of each job.
2) Executing a trigger command.
The write state is relatively small, on the order of hundreds of bytes to single
kilobytes. It contains information on the number of completions done, the last X
completions, etc.
A trigger is invoked either through creation ('touch') of a specified file in the system,
or through a timeout setting. If fio is run with `--trigger-file=/tmp/trigger-file', then
it will continually check for the existence of `/tmp/trigger-file'. When it sees this
file, it will fire off the trigger (thus saving state, and executing the trigger command).
For client/server runs, there's both a local and remote trigger. If fio is running as a
server backend, it will send the job states back to the client for safe storage, then
execute the remote trigger, if specified. If a local trigger is specified, the server will
still send back the write state, but the client will then execute the trigger.
Verification trigger example
Let's say we want to run a powercut test on the remote Linux machine 'server'. Our
write workload is in `write-test.fio'. We want to cut power to 'server' at some
point during the run, and we'll run this test from the safety or our local machine,
'localbox'. On the server, we'll start the fio backend normally:
server# fio --server
and on the client, we'll fire off the workload:
localbox$ fio --client=server --trigger-file=/tmp/my-trigger
--trigger-remote="bash -c "echo b > /proc/sysrq-triger""
We set `/tmp/my-trigger' as the trigger file, and we tell fio to execute:
echo b > /proc/sysrq-trigger
on the server once it has received the trigger and sent us the write state. This
will work, but it's not really cutting power to the server, it's merely abruptly
rebooting it. If we have a remote way of cutting power to the server through IPMI
or similar, we could do that through a local trigger command instead. Let's assume
we have a script that does IPMI reboot of a given hostname, ipmi-reboot. On
localbox, we could then have run fio with a local trigger instead:
localbox$ fio --client=server --trigger-file=/tmp/my-trigger
--trigger="ipmi-reboot server"
For this case, fio would wait for the server to send us the write state, then
execute `ipmi-reboot server' when that happened.
Loading verify state
To load stored write state, a read verification job file must contain the
verify_state_load option. If that is set, fio will load the previously stored
state. For a local fio run this is done by loading the files directly, and on a
client/server run, the server backend will ask the client to send the files over
and load them from there.
LOG FILE FORMATS
Fio supports a variety of log file formats, for logging latencies, bandwidth, and IOPS.
The logs share a common format, which looks like this:
time (msec), value, data direction, block size (bytes), offset (bytes), command
priority
`Time' for the log entry is always in milliseconds. The `value' logged depends on the type
of log, it will be one of the following:
Latency log
Value is latency in nsecs
Bandwidth log
Value is in KiB/sec
IOPS log
Value is IOPS
`Data direction' is one of the following:
0 I/O is a READ
1 I/O is a WRITE
2 I/O is a TRIM
The entry's `block size' is always in bytes. The `offset' is the position in bytes from
the start of the file for that particular I/O. The logging of the offset can be toggled
with log_offset.
If log_prio is not set, the entry's `Command priority` is 1 for an IO executed with the
highest RT priority class (prioclass=1 or cmdprio_class=1) and 0 otherwise. This is
controlled by the prioclass option and the ioengine specific cmdprio_percentage
cmdprio_class options. If log_prio is set, the entry's `Command priority` is the priority
set for the IO, as a 16-bits hexadecimal number with the lowest 13 bits indicating the
priority value (prio and cmdprio options) and the highest 3 bits indicating the IO
priority class (prioclass and cmdprio_class options).
Fio defaults to logging every individual I/O but when windowed logging is set through
log_avg_msec, either the average (by default) or the maximum (log_max_value is set)
`value' seen over the specified period of time is recorded. Each `data direction' seen
within the window period will aggregate its values in a separate row. Further, when using
windowed logging the `block size' and `offset' entries will always contain 0.
CLIENT / SERVER
Normally fio is invoked as a stand-alone application on the machine where the I/O workload
should be generated. However, the backend and frontend of fio can be run separately i.e.,
the fio server can generate an I/O workload on the "Device Under Test" while being
controlled by a client on another machine.
Start the server on the machine which has access to the storage DUT:
$ fio --server=args
where `args' defines what fio listens to. The arguments are of the form `type,hostname' or
`IP,port'. `type' is either `ip' (or ip4) for TCP/IP v4, `ip6' for TCP/IP v6, or `sock'
for a local unix domain socket. `hostname' is either a hostname or IP address, and `port'
is the port to listen to (only valid for TCP/IP, not a local socket). Some examples:
1) fio --server
Start a fio server, listening on all interfaces on the default port (8765).
2) fio --server=ip:hostname,4444
Start a fio server, listening on IP belonging to hostname and on port 4444.
3) fio --server=ip6:::1,4444
Start a fio server, listening on IPv6 localhost ::1 and on port 4444.
4) fio --server=,4444
Start a fio server, listening on all interfaces on port 4444.
5) fio --server=1.2.3.4
Start a fio server, listening on IP 1.2.3.4 on the default port.
6) fio --server=sock:/tmp/fio.sock
Start a fio server, listening on the local socket `/tmp/fio.sock'.
Once a server is running, a "client" can connect to the fio server with:
$ fio <local-args> --client=<server> <remote-args> <job file(s)>
where `local-args' are arguments for the client where it is running, `server' is the
connect string, and `remote-args' and `job file(s)' are sent to the server. The `server'
string follows the same format as it does on the server side, to allow IP/hostname/socket
and port strings.
Fio can connect to multiple servers this way:
$ fio --client=<server1> <job file(s)> --client=<server2> <job file(s)>
If the job file is located on the fio server, then you can tell the server to load a local
file as well. This is done by using --remote-config:
$ fio --client=server --remote-config /path/to/file.fio
Then fio will open this local (to the server) job file instead of being passed one from
the client.
If you have many servers (example: 100 VMs/containers), you can input a pathname of a file
containing host IPs/names as the parameter value for the --client option. For example,
here is an example `host.list' file containing 2 hostnames:
host1.your.dns.domain
host2.your.dns.domain
The fio command would then be:
$ fio --client=host.list <job file(s)>
In this mode, you cannot input server-specific parameters or job files -- all servers
receive the same job file.
In order to let `fio --client' runs use a shared filesystem from multiple hosts, `fio
--client' now prepends the IP address of the server to the filename. For example, if fio
is using the directory `/mnt/nfs/fio' and is writing filename `fileio.tmp', with a
--client `hostfile' containing two hostnames `h1' and `h2' with IP addresses
192.168.10.120 and 192.168.10.121, then fio will create two files:
/mnt/nfs/fio/192.168.10.120.fileio.tmp
/mnt/nfs/fio/192.168.10.121.fileio.tmp
Terse output in client/server mode will differ slightly from what is produced when fio is
run in stand-alone mode. See the terse output section for details.
AUTHORS
fio was written by Jens Axboe <axboe@kernel.dk>.
This man page was written by Aaron Carroll <aaronc@cse.unsw.edu.au> based on documentation
by Jens Axboe.
This man page was rewritten by Tomohiro Kusumi <tkusumi@tuxera.com> based on documentation
by Jens Axboe.
REPORTING BUGS
Report bugs to the fio mailing list <fio@vger.kernel.org>.
See REPORTING-BUGS.
REPORTING-BUGS: http://git.kernel.dk/cgit/fio/plain/REPORTING-BUGS
SEE ALSO
For further documentation see HOWTO and README.
Sample jobfiles are available in the `examples/' directory.
These are typically located under `/usr/share/doc/fio'.
HOWTO: http://git.kernel.dk/cgit/fio/plain/HOWTO
README: http://git.kernel.dk/cgit/fio/plain/README