Provided by: zfs-test_2.2.2-0ubuntu9.4_amd64 
NAME
ztest — was written by the ZFS Developers as a ZFS unit test
SYNOPSIS
ztest [-VEG] [-v vdevs] [-s size_of_each_vdev] [-a alignment_shift] [-m mirror_copies]
[-r raidz_disks/draid_disks] [-R raid_parity] [-K raid_kind] [-D draid_data] [-S draid_spares]
[-C vdev_class_state] [-d datasets] [-t threads] [-g gang_block_threshold]
[-i initialize_pool_i_times] [-k kill_percentage] [-p pool_name] [-T time] [-z zil_failure_rate]
DESCRIPTION
ztest was written by the ZFS Developers as a ZFS unit test. The tool was developed in tandem with the
ZFS functionality and was executed nightly as one of the many regression test against the daily build.
As features were added to ZFS, unit tests were also added to ztest. In addition, a separate test
development team wrote and executed more functional and stress tests.
By default ztest runs for ten minutes and uses block files (stored in /tmp) to create pools rather than
using physical disks. Block files afford ztest its flexibility to play around with zpool components
without requiring large hardware configurations. However, storing the block files in /tmp may not work
for you if you have a small tmp directory.
By default is non-verbose. This is why entering the command above will result in ztest quietly executing
for 5 minutes. The -V option can be used to increase the verbosity of the tool. Adding multiple -V
options is allowed and the more you add the more chatty ztest becomes.
After the ztest run completes, you should notice many ztest.* files lying around. Once the run completes
you can safely remove these files. Note that you shouldn't remove these files during a run. You can re-
use these files in your next ztest run by using the -E option.
OPTIONS
-h, -?, --help
Print a help summary.
-v, --vdevs= (default: 5)
Number of vdevs.
-s, --vdev-size= (default: 64M)
Size of each vdev.
-a, --alignment-shift= (default: 9) (use 0 for random)
Alignment shift used in test.
-m, --mirror-copies= (default: 2)
Number of mirror copies.
-r, --raid-disks= (default: 4 for raidz/16 for draid)
Number of raidz/draid disks.
-R, --raid-parity= (default: 1)
Raid parity (raidz & draid).
-K, --raid-kind=raidz|draid|random (default: random)
The kind of RAID config to use. With random the kind alternates between raidz and draid.
-D, --draid-data= (default: 4)
Number of data disks in a dRAID redundancy group.
-S, --draid-spares= (default: 1)
Number of dRAID distributed spare disks.
-d, --datasets= (default: 7)
Number of datasets.
-t, --threads= (default: 23)
Number of threads.
-g, --gang-block-threshold= (default: 32K)
Gang block threshold.
-i, --init-count= (default: 1)
Number of pool initializations.
-k, --kill-percentage= (default: 70%)
Kill percentage.
-p, --pool-name= (default: ztest)
Pool name.
-f, --vdev-file-directory= (default: /tmp)
File directory for vdev files.
-M, --multi-host
Multi-host; simulate pool imported on remote host.
-E, --use-existing-pool
Use existing pool (use existing pool instead of creating new one).
-T, --run-time= (default: 300s)
Total test run time.
-P, --pass-time= (default: 60s)
Time per pass.
-F, --freeze-loops= (default: 50)
Max loops in spa_freeze().
-B, --alt-ztest=
Path to alternate ("older") ztest to drive, which will be used to initialise the pool, and, a
stochastic half the time, to run the tests. The parallel lib directory is prepended to
LD_LIBRARY_PATH; i.e. given -B ./chroots/lenny/usr/bin/ztest, ./chroots/lenny/usr/lib will be
loaded.
-C, --vdev-class-state=on|off|random (default: random)
The vdev allocation class state.
-o, --option=variable=value
Set global variable to an unsigned 32-bit integer value (little-endian only).
-G, --dump-debug
Dump zfs_dbgmsg buffer before exiting due to an error.
-V, --verbose
Verbose (use multiple times for ever more verbosity).
EXAMPLES
To override /tmp as your location for block files, you can use the -f option:
# ztest -f /
To get an idea of what ztest is actually testing try this:
# ztest -f / -VVV
Maybe you'd like to run ztest for longer? To do so simply use the -T option and specify the runlength in
seconds like so:
# ztest -f / -V -T 120
ENVIRONMENT VARIABLES
ZFS_HOSTID=id
Use id instead of the SPL hostid to identify this host. Intended for use with ztest, but this
environment variable will affect any utility which uses libzpool, including zpool(8). Since the
kernel is unaware of this setting, results with utilities other than ztest are undefined.
ZFS_STACK_SIZE=stacksize
Limit the default stack size to stacksize bytes for the purpose of detecting and debugging kernel
stack overflows. This value defaults to 32K which is double the default 16K Linux kernel stack size.
In practice, setting the stack size slightly higher is needed because differences in stack usage
between kernel and user space can lead to spurious stack overflows (especially when debugging is
enabled). The specified value will be rounded up to a floor of PTHREAD_STACK_MIN which is the
minimum stack required for a NULL procedure in user space.
By default the stack size is limited to 256K.
SEE ALSO
zdb(1), zfs(1), zpool(1), spl(4)
OpenZFS May 26, 2021 ZTEST(1)