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ZPOOL(8) System Manager's Manual ZPOOL(8)

zpool — configures ZFS storage pools

zpool [-?]

zpool add [-fn] pool vdev ...

zpool attach [-f] pool device new_device

zpool checkpoint [-d, --discard] pool

zpool clear [-F [-n]] pool [device]

zpool create [-fnd] [-o property=value] ... [-O file-system-property=value] ... [-m mountpoint] [-R root] [-t tempname] pool vdev ...

zpool destroy [-f] pool

zpool detach pool device

zpool export [-f] pool ...

zpool get [-Hp] [-o field[,...]] all | property[,...] pool ...

zpool history [-il] [pool] ...

zpool import [-d dir | -c cachefile] [-D]

zpool import [-o mntopts] [-o property=value] ... [--rewind-to-checkpoint] [-d dir | -c cachefile] [-D] [-f] [-m] [-N] [-R root] [-F [-n]] -a

zpool import [-o mntopts] [-o property=value] ... [--rewind-to-checkpoint] [-d dir | -c cachefile] [-D] [-f] [-m] [-N] [-R root] [-t] [-F [-n]] pool | id [newpool]

zpool initialize [-cs] pool [device...]

zpool iostat [-T d|u] [-v] [pool] ...

zpool labelclear [-f] device

zpool list [-Hpv] [-o property[,...]] [-T d|u] [pool] ... [inverval [count]]

zpool offline [-t] pool device ...

zpool online [-e] pool device ...

zpool reguid pool

zpool remove [-np] pool device ...

zpool remove -s pool

zpool reopen pool

zpool replace [-f] pool device [new_device]

zpool scrub [-s | -p] pool ...

zpool set property=value pool

zpool split [-n] [-R altroot] [-o mntopts] [-o property=value] pool newpool [device ...]

zpool status [-vx] [-T d|u] [pool] ... [interval [count]]

zpool upgrade [-v]

zpool upgrade [-V version] -a | pool ...

The zpool command configures ZFS storage pools. A storage pool is a collection of devices that provides physical storage and data replication for ZFS datasets.

All datasets within a storage pool share the same space. See zfs(8) for information on managing datasets.

A "virtual device" (vdev) describes a single device or a collection of devices organized according to certain performance and fault characteristics. The following virtual devices are supported:

A block device, typically located under /dev. ZFS can use individual slices or partitions, though the recommended mode of operation is to use whole disks. A disk can be specified by a full path to the device or the geom(4) provider name. When given a whole disk, ZFS automatically labels the disk, if necessary.
A regular file. The use of files as a backing store is strongly discouraged. It is designed primarily for experimental purposes, as the fault tolerance of a file is only as good the file system of which it is a part. A file must be specified by a full path.
A mirror of two or more devices. Data is replicated in an identical fashion across all components of a mirror. A mirror with N disks of size X can hold X bytes and can withstand () devices failing before data integrity is compromised.
(or raidz1 raidz2 raidz3). A variation on RAID-5 that allows for better distribution of parity and eliminates the "RAID-5" write hole (in which data and parity become inconsistent after a power loss). Data and parity is striped across all disks within a raidz group.

A raidz group can have single-, double- , or triple parity, meaning that the raidz group can sustain one, two, or three failures, respectively, without losing any data. The raidz1 vdev type specifies a single-parity raidz group; the vdev type specifies a double-parity raidz group; and the vdev type specifies a triple-parity raidz group. The raidz vdev type is an alias for raidz1.

A raidz group with N disks of size X with P parity disks can hold approximately ()*X bytes and can withstand P device(s) failing before data integrity is compromised. The minimum number of devices in a raidz group is one more than the number of parity disks. The recommended number is between 3 and 9 to help increase performance.

A special pseudo-vdev which keeps track of available hot spares for a pool. For more information, see the "Hot Spares" section.
A separate-intent log device. If more than one log device is specified, then writes are load-balanced between devices. Log devices can be mirrored. However, raidz vdev types are not supported for the intent log. For more information, see the "Intent Log" section.
A device used to cache storage pool data. A cache device cannot be configured as a mirror or raidz group. For more information, see the "Cache Devices" section.

Virtual devices cannot be nested, so a mirror or raidz virtual device can only contain files or disks. Mirrors of mirrors (or other combinations) are not allowed.

A pool can have any number of virtual devices at the top of the configuration (known as "root" vdevs). Data is dynamically distributed across all top-level devices to balance data among devices. As new virtual devices are added, ZFS automatically places data on the newly available devices.

Virtual devices are specified one at a time on the command line, separated by whitespace. The keywords "mirror" and "raidz" are used to distinguish where a group ends and another begins. For example, the following creates two root vdevs, each a mirror of two disks:

# zpool create mypool mirror da0 da1 mirror da2 da3

ZFS supports a rich set of mechanisms for handling device failure and data corruption. All metadata and data is checksummed, and ZFS automatically repairs bad data from a good copy when corruption is detected.

In order to take advantage of these features, a pool must make use of some form of redundancy, using either mirrored or raidz groups. While ZFS supports running in a non-redundant configuration, where each root vdev is simply a disk or file, this is strongly discouraged. A single case of bit corruption can render some or all of your data unavailable.

A pool's health status is described by one of three states: online, degraded, or faulted. An online pool has all devices operating normally. A degraded pool is one in which one or more devices have failed, but the data is still available due to a redundant configuration. A faulted pool has corrupted metadata, or one or more faulted devices, and insufficient replicas to continue functioning.

The health of the top-level vdev, such as mirror or raidz device, is potentially impacted by the state of its associated vdevs, or component devices. A top-level vdev or component device is in one of the following states:

One or more top-level vdevs is in the degraded state because one or more component devices are offline. Sufficient replicas exist to continue functioning.

One or more component devices is in the degraded or faulted state, but sufficient replicas exist to continue functioning. The underlying conditions are as follows:

  • The number of checksum errors exceeds acceptable levels and the device is degraded as an indication that something may be wrong. ZFS continues to use the device as necessary.
  • The number of I/O errors exceeds acceptable levels. The device could not be marked as faulted because there are insufficient replicas to continue functioning.
One or more top-level vdevs is in the faulted state because one or more component devices are offline. Insufficient replicas exist to continue functioning.

One or more component devices is in the faulted state, and insufficient replicas exist to continue functioning. The underlying conditions are as follows:

  • The device could be opened, but the contents did not match expected values.
  • The number of I/O errors exceeds acceptable levels and the device is faulted to prevent further use of the device.
The device was explicitly taken offline by the "zpool offline" command.
The device is online and functioning.
The device was physically removed while the system was running. Device removal detection is hardware-dependent and may not be supported on all platforms.
The device could not be opened. If a pool is imported when a device was unavailable, then the device will be identified by a unique identifier instead of its path since the path was never correct in the first place.

If a device is removed and later reattached to the system, ZFS attempts to put the device online automatically. Device attach detection is hardware-dependent and might not be supported on all platforms.

ZFS allows devices to be associated with pools as "hot spares". These devices are not actively used in the pool, but when an active device fails, it is automatically replaced by a hot spare. To create a pool with hot spares, specify a "spare" vdev with any number of devices. For example,

# zpool create pool mirror da0 da1 spare da2 da3

Spares can be shared across multiple pools, and can be added with the "zpool add" command and removed with the "zpool remove" command. Once a spare replacement is initiated, a new "spare" vdev is created within the configuration that will remain there until the original device is replaced. At this point, the hot spare becomes available again if another device fails.

If a pool has a shared spare that is currently being used, the pool can not be exported since other pools may use this shared spare, which may lead to potential data corruption.

An in-progress spare replacement can be cancelled by detaching the hot spare. If the original faulted device is detached, then the hot spare assumes its place in the configuration, and is removed from the spare list of all active pools.

Spares cannot replace log devices.

This feature requires a userland helper. FreeBSD provides zfsd(8) for this purpose. It must be manually enabled by adding zfsd_enable="YES" to /etc/rc.conf.

The ZFS Intent Log (ZIL) satisfies POSIX requirements for synchronous transactions. For instance, databases often require their transactions to be on stable storage devices when returning from a system call. NFS and other applications can also use fsync(2) to ensure data stability. By default, the intent log is allocated from blocks within the main pool. However, it might be possible to get better performance using separate intent log devices such as NVRAM or a dedicated disk. For example:

# zpool create pool da0 da1 log da2

Multiple log devices can also be specified, and they can be mirrored. See the EXAMPLES section for an example of mirroring multiple log devices.

Log devices can be added, replaced, attached, detached, imported and exported as part of the larger pool. Mirrored devices can be removed by specifying the top-level mirror vdev.

Devices can be added to a storage pool as "cache devices." These devices provide an additional layer of caching between main memory and disk. For read-heavy workloads, where the working set size is much larger than what can be cached in main memory, using cache devices allow much more of this working set to be served from low latency media. Using cache devices provides the greatest performance improvement for random read-workloads of mostly static content.

To create a pool with cache devices, specify a "cache" vdev with any number of devices. For example:

# zpool create pool da0 da1 cache da2 da3

Cache devices cannot be mirrored or part of a raidz configuration. If a read error is encountered on a cache device, that read I/O is reissued to the original storage pool device, which might be part of a mirrored or raidz configuration.

The content of the cache devices is considered volatile, as is the case with other system caches.

Before starting critical procedures that include destructive actions (e.g zfs destroy ), an administrator can checkpoint the pool's state and in the case of a mistake or failure, rewind the entire pool back to the checkpoint. Otherwise, the checkpoint can be discarded when the procedure has completed successfully.

A pool checkpoint can be thought of as a pool-wide snapshot and should be used with care as it contains every part of the pool's state, from properties to vdev configuration. Thus, while a pool has a checkpoint certain operations are not allowed. Specifically, vdev removal/attach/detach, mirror splitting, and changing the pool's guid. Adding a new vdev is supported but in the case of a rewind it will have to be added again. Finally, users of this feature should keep in mind that scrubs in a pool that has a checkpoint do not repair checkpointed data.

To create a checkpoint for a pool:

# zpool checkpoint pool

To later rewind to its checkpointed state, you need to first export it and then rewind it during import:

# zpool export pool
# zpool import --rewind-to-checkpoint pool

To discard the checkpoint from a pool:

# zpool checkpoint -d pool

Dataset reservations (controlled by the reservation or refreservation zfs properties) may be unenforceable while a checkpoint exists, because the checkpoint is allowed to consume the dataset's reservation. Finally, data that is part of the checkpoint but has been freed in the current state of the pool won't be scanned during a scrub.

Each pool has several properties associated with it. Some properties are read-only statistics while others are configurable and change the behavior of the pool. The following are read-only properties:

Amount of storage space within the pool that has been physically allocated.
Percentage of pool space used. This property can also be referred to by its shortened column name, "cap".
A text string consisting of printable ASCII characters that will be stored such that it is available even if the pool becomes faulted. An administrator can provide additional information about a pool using this property.
The deduplication ratio specified for a pool, expressed as a multiplier. For example, a dedupratio value of 1.76 indicates that 1.76 units of data were stored but only 1 unit of disk space was actually consumed. See zfs(8) for a description of the deduplication feature.
Amount of uninitialized space within the pool or device that can be used to increase the total capacity of the pool. Uninitialized space consists of any space on an EFI labeled vdev which has not been brought online (i.e. zpool online -e). This space occurs when a LUN is dynamically expanded.
The amount of fragmentation in the pool.
Number of blocks within the pool that are not allocated.
After a file system or snapshot is destroyed, the space it was using is returned to the pool asynchronously. freeing is the amount of space remaining to be reclaimed. Over time freeing will decrease while free increases.
A unique identifier for the pool.
The current health of the pool. Health can be "ONLINE", "DEGRADED", "FAULTED", "OFFLINE", "REMOVED", or "UNAVAIL".
Total size of the storage pool.
feature_guid
Information about unsupported features that are enabled on the pool. See zpool-features(7) for details.
Amount of storage space used within the pool.

The space usage properties report actual physical space available to the storage pool. The physical space can be different from the total amount of space that any contained datasets can actually use. The amount of space used in a raidz configuration depends on the characteristics of the data being written. In addition, ZFS reserves some space for internal accounting that the zfs(8) command takes into account, but the zpool(8) command does not. For non-full pools of a reasonable size, these effects should be invisible. For small pools, or pools that are close to being completely full, these discrepancies may become more noticeable.

The following property can be set at creation time and import time:

Alternate root directory. If set, this directory is prepended to any mount points within the pool. This can be used when examining an unknown pool where the mount points cannot be trusted, or in an alternate boot environment, where the typical paths are not valid. altroot is not a persistent property. It is valid only while the system is up. Setting altroot defaults to using cachefile=none, though this may be overridden using an explicit setting.

The following property can only be set at import time:

=on |
If set to on, pool will be imported in read-only mode with the following restrictions:
  • Synchronous data in the intent log will not be accessible
  • Properties of the pool can not be changed
  • Datasets of this pool can only be mounted read-only
  • To write to a read-only pool, a export and import of the pool is required.

This property can also be referred to by its shortened column name, .

The following properties can be set at creation time and import time, and later changed with the zpool set command:

=on |
Controls automatic pool expansion when the underlying LUN is grown. If set to "on", the pool will be resized according to the size of the expanded device. If the device is part of a mirror or raidz then all devices within that mirror/raidz group must be expanded before the new space is made available to the pool. The default behavior is "off". This property can also be referred to by its shortened column name, .
=on |
Controls automatic device replacement. If set to "off", device replacement must be initiated by the administrator by using the "zpool replace" command. If set to "on", any new device, found in the same physical location as a device that previously belonged to the pool, is automatically formatted and replaced. The default behavior is "off". This property can also be referred to by its shortened column name, "replace".
=pool/dataset
Identifies the default bootable dataset for the root pool. This property is expected to be set mainly by the installation and upgrade programs.
=path |
Controls the location of where the pool configuration is cached. Discovering all pools on system startup requires a cached copy of the configuration data that is stored on the root file system. All pools in this cache are automatically imported when the system boots. Some environments, such as install and clustering, need to cache this information in a different location so that pools are not automatically imported. Setting this property caches the pool configuration in a different location that can later be imported with "zpool import -c". Setting it to the special value "none" creates a temporary pool that is never cached, and the special value '' (empty string) uses the default location.
=text
A text string consisting of printable ASCII characters that will be stored such that it is available even if the pool becomes faulted. An administrator can provide additional information about a pool using this property.
=number
Threshold for the number of block ditto copies. If the reference count for a deduplicated block increases above this number, a new ditto copy of this block is automatically stored. Default setting is 0 which causes no ditto copies to be created for deduplicated blocks. The miniumum legal nonzero setting is 100.
=on |
Controls whether a non-privileged user is granted access based on the dataset permissions defined on the dataset. See zfs(8) for more information on ZFS delegated administration.
=wait | |
Controls the system behavior in the event of catastrophic pool failure. This condition is typically a result of a loss of connectivity to the underlying storage device(s) or a failure of all devices within the pool. The behavior of such an event is determined as follows:
Blocks all I/O access until the device connectivity is recovered and the errors are cleared. This is the default behavior.
Returns to any new write I/O requests but allows reads to any of the remaining healthy devices. Any write requests that have yet to be committed to disk would be blocked.
Prints out a message to the console and generates a system crash dump.
feature_name=enabled
The value of this property is the current state of feature_name. The only valid value when setting this property is enabled which moves feature_name to the enabled state. See zpool-features(7) for details on feature states.
=on |
Controls whether information about snapshots associated with this pool is output when "zfs list" is run without the -t option. The default value is off.
=version
The current on-disk version of the pool. This can be increased, but never decreased. The preferred method of updating pools is with the "zpool upgrade" command, though this property can be used when a specific version is needed for backwards compatibility. Once feature flags is enabled on a pool this property will no longer have a value.

All subcommands that modify state are logged persistently to the pool in their original form.

The zpool command provides subcommands to create and destroy storage pools, add capacity to storage pools, and provide information about the storage pools. The following subcommands are supported:

zpool [-?]

Displays a help message.

zpool add [-fn] pool vdev ...

Adds the specified virtual devices to the given pool. The vdev specification is described in the "Virtual Devices" section. The behavior of the -f option, and the device checks performed are described in the "zpool create" subcommand.

Forces use of vdev, even if they appear in use or specify a conflicting replication level. Not all devices can be overridden in this manner.
Displays the configuration that would be used without actually adding the vdevs. The actual pool creation can still fail due to insufficient privileges or device sharing.

Do not add a disk that is currently configured as a quorum device to a zpool. After a disk is in the pool, that disk can then be configured as a quorum device.

zpool attach [-f] pool device new_device

Attaches new_device to an existing device. The existing device cannot be part of a raidz configuration. If device is not currently part of a mirrored configuration, device automatically transforms into a two-way mirror of device and new_device. If device is part of a two-way mirror, attaching new_device creates a three-way mirror, and so on. In either case, new_device begins to resilver immediately.

Forces use of new_device, even if its appears to be in use. Not all devices can be overridden in this manner.
zpool checkpoint [-d, --discard] pool
Checkpoints the current state of pool , which can be later restored by zpool import --rewind-to-checkpoint. The existence of a checkpoint in a pool prohibits the following zpool commands: remove, attach, detach, split, and reguid. In addition, it may break reservation boundaries if the pool lacks free space. The zpool status command indicates the existence of a checkpoint or the progress of discarding a checkpoint from a pool. The zpool list command reports how much space the checkpoint takes from the pool.
--discard
Discards an existing checkpoint from pool.
zpool clear [-F [-n]] pool [device]

Clears device errors in a pool. If no arguments are specified, all device errors within the pool are cleared. If one or more devices is specified, only those errors associated with the specified device or devices are cleared.

Initiates recovery mode for an unopenable pool. Attempts to discard the last few transactions in the pool to return it to an openable state. Not all damaged pools can be recovered by using this option. If successful, the data from the discarded transactions is irretrievably lost.
Used in combination with the -F flag. Check whether discarding transactions would make the pool openable, but do not actually discard any transactions.
zpool create [-fnd] [-o property=value] ... [-O file-system-property=value] ... [-m mountpoint] [-R root] [-t tempname] pool vdev ...

Creates a new storage pool containing the virtual devices specified on the command line. The pool name must begin with a letter, and can only contain alphanumeric characters as well as underscore ("_"), dash ("-"), and period ("."). The pool names "mirror", "raidz", "spare" and "log" are reserved, as are names beginning with the pattern "c[0-9]". The vdev specification is described in the "Virtual Devices" section.

The command verifies that each device specified is accessible and not currently in use by another subsystem. There are some uses, such as being currently mounted, or specified as the dedicated dump device, that prevents a device from ever being used by ZFS Other uses, such as having a preexisting file system, can be overridden with the -f option.

The command also checks that the replication strategy for the pool is consistent. An attempt to combine redundant and non-redundant storage in a single pool, or to mix disks and files, results in an error unless -f is specified. The use of differently sized devices within a single raidz or mirror group is also flagged as an error unless -f is specified.

Unless the -R option is specified, the default mount point is "/pool". The mount point must not exist or must be empty, or else the root dataset cannot be mounted. This can be overridden with the -m option.

By default all supported features are enabled on the new pool unless the -d option is specified.

Forces use of vdevs, even if they appear in use or specify a conflicting replication level. Not all devices can be overridden in this manner.
Displays the configuration that would be used without actually creating the pool. The actual pool creation can still fail due to insufficient privileges or device sharing.
Do not enable any features on the new pool. Individual features can be enabled by setting their corresponding properties to enabled with the -o option. See zpool-features(7) for details about feature properties.
property=value [-o property=value] ...
Sets the given pool properties. See the "Properties" section for a list of valid properties that can be set.
file-system-property=value [-O file-system-property=value] ...
Sets the given file system properties in the root file system of the pool. See zfs(8) Properties for a list of valid properties that can be set.
root
Equivalent to "-o cachefile=none,altroot=root"
mountpoint
Sets the mount point for the root dataset. The default mount point is "/pool" or "altroot/pool" if altroot is specified. The mount point must be an absolute path, "legacy", or "none". For more information on dataset mount points, see zfs(8).
tempname
Sets the in-core pool name to tempname while the on-disk name will be the name specified as the pool name pool. This will set the default cachefile property to none. This is intended to handle name space collisions when creating pools for other systems, such as virtual machines or physical machines whose pools live on network block devices.
zpool destroy [-f] pool

Destroys the given pool, freeing up any devices for other use. This command tries to unmount any active datasets before destroying the pool.

Forces any active datasets contained within the pool to be unmounted.
zpool detach pool device

Detaches device from a mirror. The operation is refused if there are no other valid replicas of the data.

zpool export [-f] pool ...

Exports the given pools from the system. All devices are marked as exported, but are still considered in use by other subsystems. The devices can be moved between systems (even those of different endianness) and imported as long as a sufficient number of devices are present.

Before exporting the pool, all datasets within the pool are unmounted. A pool can not be exported if it has a shared spare that is currently being used.

For pools to be portable, you must give the zpool command whole disks, not just slices, so that ZFS can label the disks with portable labels. Otherwise, disk drivers on platforms of different endianness will not recognize the disks.

Forcefully unmount all datasets, using the "unmount -f" command.

This command will forcefully export the pool even if it has a shared spare that is currently being used. This may lead to potential data corruption.

zpool get [-Hp] [-o field[,...]] all | property[,...] pool ...

Retrieves the given list of properties (or all properties if "all" is used) for the specified storage pool(s). These properties are displayed with the following fields:

name Name of storage pool
property Property name
value Property value
source Property source, either 'default' or 'local'.

See the "Properties" section for more information on the available pool properties.

Scripted mode. Do not display headers, and separate fields by a single tab instead of arbitrary space.
Display numbers in parsable (exact) values.
field
A comma-separated list of columns to display. name,,, is the default value.
zpool history [-il] [pool] ...

Displays the command history of the specified pools or all pools if no pool is specified.

Displays internally logged ZFS events in addition to user initiated events.
Displays log records in long format, which in addition to standard format includes, the user name, the hostname, and the zone in which the operation was performed.
zpool import [-d dir | -c cachefile] [-D]

Lists pools available to import. If the -d option is not specified, this command searches for devices in "/dev". The -d option can be specified multiple times, and all directories are searched. If the device appears to be part of an exported pool, this command displays a summary of the pool with the name of the pool, a numeric identifier, as well as the vdev layout and current health of the device for each device or file. Destroyed pools, pools that were previously destroyed with the "zpool destroy" command, are not listed unless the -D option is specified.

The numeric identifier is unique, and can be used instead of the pool name when multiple exported pools of the same name are available.

cachefile
Reads configuration from the given cachefile that was created with the "cachefile" pool property. This cachefile is used instead of searching for devices.
dir
Searches for devices or files in dir. The -d option can be specified multiple times.
Lists destroyed pools only.
zpool import [-o mntopts] [-o property=value] ... [-d dir | -c cachefile] [-D] [-f] [-m] [-N] [-R root] [-F [-n]] -a

Imports all pools found in the search directories. Identical to the previous command, except that all pools with a sufficient number of devices available are imported. Destroyed pools, pools that were previously destroyed with the "zpool destroy" command, will not be imported unless the -D option is specified.

mntopts
Comma-separated list of mount options to use when mounting datasets within the pool. See zfs(8) for a description of dataset properties and mount options.
property=value
Sets the specified property on the imported pool. See the "Properties" section for more information on the available pool properties.
cachefile
Reads configuration from the given cachefile that was created with the "cachefile" pool property. This cachefile is used instead of searching for devices.
dir
Searches for devices or files in dir. The -d option can be specified multiple times. This option is incompatible with the -c option.
Imports destroyed pools only. The -f option is also required.
Forces import, even if the pool appears to be potentially active.
Allows a pool to import when there is a missing log device. Recent transactions can be lost because the log device will be discarded.
Import the pool without mounting any file systems.
root
Sets the "cachefile" property to "none" and the "altroot" property to "root"
Recovery mode for a non-importable pool. Attempt to return the pool to an importable state by discarding the last few transactions. Not all damaged pools can be recovered by using this option. If successful, the data from the discarded transactions is irretrievably lost. This option is ignored if the pool is importable or already imported.
Used with the -F recovery option. Determines whether a non-importable pool can be made importable again, but does not actually perform the pool recovery. For more details about pool recovery mode, see the -F option, above.
Searches for and imports all pools found.
zpool import [-o mntopts] [-o property=value] ... [-d dir | -c cachefile] [-D] [-f] [-m] [-N] [-R root] [-t] [-F [-n]] pool | id [newpool]

Imports a specific pool. A pool can be identified by its name or the numeric identifier. If newpool is specified, the pool is imported using the name newpool. Otherwise, it is imported with the same name as its exported name.

If a device is removed from a system without running "zpool export" first, the device appears as potentially active. It cannot be determined if this was a failed export, or whether the device is really in use from another host. To import a pool in this state, the -f option is required.

mntopts
Comma-separated list of mount options to use when mounting datasets within the pool. See zfs(8) for a description of dataset properties and mount options.
property=value
Sets the specified property on the imported pool. See the "Properties" section for more information on the available pool properties.
cachefile
Reads configuration from the given cachefile that was created with the "cachefile" pool property. This cachefile is used instead of searching for devices.
dir
Searches for devices or files in dir. The -d option can be specified multiple times. This option is incompatible with the -c option.
Imports destroyed pools only. The -f option is also required.
Forces import, even if the pool appears to be potentially active.
Allows a pool to import when there is a missing log device. Recent transactions can be lost because the log device will be discarded.
Import the pool without mounting any file systems.
root
Equivalent to "-o cachefile=none,altroot=root"
Used with newpool. Specifies that newpool is temporary. Temporary pool names last until export. Ensures that the original pool name will be used in all label updates and therefore is retained upon export. Will also set cachefile property to none when not explicitly specified.
Recovery mode for a non-importable pool. Attempt to return the pool to an importable state by discarding the last few transactions. Not all damaged pools can be recovered by using this option. If successful, the data from the discarded transactions is irretrievably lost. This option is ignored if the pool is importable or already imported.
Used with the -F recovery option. Determines whether a non-importable pool can be made importable again, but does not actually perform the pool recovery. For more details about pool recovery mode, see the -F option, above.
Rewinds pool to the checkpointed state. Once the pool is imported with this flag there is no way to undo the rewind. All changes and data that were written after the checkpoint are lost! The only exception is when the readonly mounting option is enabled. In this case, the checkpointed state of the pool is opened and an administrator can see how the pool would look like if they were to fully rewind.
zpool initialize [-cs] pool [device...]
Begins initializing by writing to all unallocated regions on the specified devices, or all eligible devices in the pool if no individual devices are specified. Only leaf data or log devices may be initialized.
--cancel
Cancel initializing on the specified devices, or all eligible devices if none are specified. If one or more target devices are invalid or are not currently being initialized, the command will fail and no cancellation will occur on any device.
--suspend
Suspend initializing on the specified devices, or all eligible devices if none are specified. If one or more target devices are invalid or are not currently being initialized, the command will fail and no suspension will occur on any device. Initializing can then be resumed by running zpool initialize with no flags on the relevant target devices.
zpool iostat [-T d|u] [-v] [pool] ... [interval [count]]

Displays I/O statistics for the given pools. When given an interval, the statistics are printed every interval seconds until Ctrl-C is pressed. If no pools are specified, statistics for every pool in the system is shown. If count is specified, the command exits after count reports are printed.

d|u
Print a timestamp.

Use modifier d for standard date format. See date(1). Use modifier u for unixtime (equals "date +%s").

Verbose statistics. Reports usage statistics for individual vdevs within the pool, in addition to the pool-wide statistics.
zpool labelclear [-f] device

Removes ZFS label information from the specified device. The device must not be part of an active pool configuration.

Treat exported or foreign devices as inactive.
zpool list [-Hpv] [-o property[,...]] [-T d|u] [pool] ... [inverval [count]]

Lists the given pools along with a health status and space usage. If no pools are specified, all pools in the system are listed.

When given an interval, the output is printed every interval seconds until Ctrl-C is pressed. If count is specified, the command exits after count reports are printed.

d|u
Print a timestamp.

Use modifier d for standard date format. See date(1). Use modifier u for unixtime (equals "date +%s").

Scripted mode. Do not display headers, and separate fields by a single tab instead of arbitrary space.
Display numbers in parsable (exact) values.
Verbose statistics. Reports usage statistics for individual within the pool, in addition to the pool-wide statistics.
property[,...]
Comma-separated list of properties to display. See the "Properties" section for a list of valid properties. The default list is name, size, used, , , expandsize, fragmentation, capacity, dedupratio, health, altroot.
d|u
Print a timestamp.

Use modifier d for standard date format. See date(1). Use modifier u for unixtime (equals "date +%s").

zpool offline [-t] pool device ...

Takes the specified physical device offline. While the device is offline, no attempt is made to read or write to the device.

Temporary. Upon reboot, the specified physical device reverts to its previous state.
zpool online [-e] pool device ...

Brings the specified physical device online.

This command is not applicable to spares or cache devices.

Expand the device to use all available space. If the device is part of a mirror or raidz then all devices must be expanded before the new space will become available to the pool.
zpool reguid pool

Generates a new unique identifier for the pool. You must ensure that all devices in this pool are online and healthy before performing this action.

zpool remove [-np] pool device ...

Removes the specified device from the pool. This command currently only supports removing hot spares, cache, log devices and mirrored top-level vdevs (mirror of leaf devices); but not raidz.

Removing a top-level vdev reduces the total amount of space in the storage pool. The specified device will be evacuated by copying all allocated space from it to the other devices in the pool. In this case, the zpool remove command initiates the removal and returns, while the evacuation continues in the background. The removal progress can be monitored with zpool status. This feature must be enabled to be used, see zpool-features(5)

A mirrored top-level device (log or data) can be removed by specifying the top-level mirror for the same. Non-log devices or data devices that are part of a mirrored configuration can be removed using the "zpool detach" command.

Do not actually perform the removal ("no-op"). Instead, print the estimated amount of memory that will be used by the mapping table after the removal completes. This is nonzero only for top-level vdevs.
Used in conjunction with the -n flag, displays numbers as parsable (exact) values.
zpool remove -s pool

Stops and cancels an in-progress removal of a top-level vdev.

zpool reopen pool

Reopen all the vdevs associated with the pool.

zpool replace [-f] pool device [new_device]

Replaces old_device with new_device. This is equivalent to attaching new_device, waiting for it to resilver, and then detaching old_device.

The size of new_device must be greater than or equal to the minimum size of all the devices in a mirror or raidz configuration.

new_device is required if the pool is not redundant. If new_device is not specified, it defaults to old_device. This form of replacement is useful after an existing disk has failed and has been physically replaced. In this case, the new disk may have the same /dev path as the old device, even though it is actually a different disk. ZFS recognizes this.

Forces use of new_device, even if its appears to be in use. Not all devices can be overridden in this manner.
zpool scrub [-s | -p] pool ...

Begins a scrub or resumes a paused scrub. The scrub examines all data in the specified pools to verify that it checksums correctly. For replicated (mirror or raidz) devices, ZFS automatically repairs any damage discovered during the scrub. The zpool status command reports the progress of the scrub and summarizes the results of the scrub upon completion.

Scrubbing and resilvering are very similar operations. The difference is that resilvering only examines data that ZFS knows to be out of date (for example, when attaching a new device to a mirror or replacing an existing device), whereas scrubbing examines all data to discover silent errors due to hardware faults or disk failure.

Because scrubbing and resilvering are I/O-intensive operations, ZFS only allows one at a time. If a scrub is paused, the zpool scrub resumes it. If a resilver is in progress, ZFS does not allow a scrub to be started until the resilver completes.

Stop scrubbing.
Pause scrubbing. Scrub pause state and progress are periodically synced to disk. If the system is restarted or pool is exported during a paused scrub, even after import, scrub will remain paused until it is resumed. Once resumed the scrub will pick up from the place where it was last checkpointed to disk. To resume a paused scrub issue zpool scrub again.
zpool set property=value pool

Sets the given property on the specified pool. See the "Properties" section for more information on what properties can be set and acceptable values.

zpool split [-n] [-R altroot] [-o mntopts] [-o property=value] pool newpool [device ...]

Splits off one disk from each mirrored top-level vdev in a pool and creates a new pool from the split-off disks. The original pool must be made up of one or more mirrors and must not be in the process of resilvering. The split subcommand chooses the last device in each mirror vdev unless overridden by a device specification on the command line.

When using a device argument, split includes the specified device(s) in a new pool and, should any devices remain unspecified, assigns the last device in each mirror vdev to that pool, as it does normally. If you are uncertain about the outcome of a split command, use the -n ("dry-run") option to ensure your command will have the effect you intend.

altroot
Automatically import the newly created pool after splitting, using the specified altroot parameter for the new pool's alternate root. See the altroot description in the "Properties" section, above.
Displays the configuration that would be created without actually splitting the pool. The actual pool split could still fail due to insufficient privileges or device status.
mntopts
Comma-separated list of mount options to use when mounting datasets within the pool. See zfs(8) for a description of dataset properties and mount options. Valid only in conjunction with the -R option.
property=value
Sets the specified property on the new pool. See the "Properties" section, above, for more information on the available pool properties.
zpool status [-vx] [-T d|u] [pool] ... [interval [count]]

Displays the detailed health status for the given pools. If no pool is specified, then the status of each pool in the system is displayed. For more information on pool and device health, see the "Device Failure and Recovery" section.

When given an interval, the output is printed every interval seconds until Ctrl-C is pressed. If count is specified, the command exits after count reports are printed.

If a scrub or resilver is in progress, this command reports the percentage done and the estimated time to completion. Both of these are only approximate, because the amount of data in the pool and the other workloads on the system can change.

Only display status for pools that are exhibiting errors or are otherwise unavailable. Warnings about pools not using the latest on-disk format, having non-native block size or disabled features will not be included.
Displays verbose data error information, printing out a complete list of all data errors since the last complete pool scrub.
d|u
Print a timestamp.

Use modifier d for standard date format. See date(1). Use modifier u for unixtime (equals "date +%s").

zpool upgrade [-v]

Displays pools which do not have all supported features enabled and pools formatted using a legacy ZFS version number. These pools can continue to be used, but some features may not be available. Use zpool upgrade -a to enable all features on all pools.

Displays legacy ZFS versions supported by the current software. See zpool-features(7) for a description of feature flags features supported by the current software.
zpool upgrade [-V version] -a | pool ...

Enables all supported features on the given pool. Once this is done, the pool will no longer be accessible on systems that do not support feature flags. See zpool-features(7) for details on compatibility with systems that support feature flags, but do not support all features enabled on the pool.

Enables all supported features on all pools.
version
Upgrade to the specified legacy version. If the -V flag is specified, no features will be enabled on the pool. This option can only be used to increase version number up to the last supported legacy version number.

The following exit values are returned:

0
Successful completion.
1
An error occurred.
2
Invalid command line options were specified.

Creating a RAID-Z Storage Pool

The following command creates a pool with a single raidz root vdev that consists of six disks.

# zpool create tank raidz da0 da1 da2 da3 da4 da5
Creating a Mirrored Storage Pool

The following command creates a pool with two mirrors, where each mirror contains two disks.

# zpool create tank mirror da0 da1 mirror da2 da3
Creating a ZFS Storage Pool by Using Partitions

The following command creates an unmirrored pool using two GPT partitions.

# zpool create tank da0p3 da1p3
Creating a ZFS Storage Pool by Using Files

The following command creates an unmirrored pool using files. While not recommended, a pool based on files can be useful for experimental purposes.

# zpool create tank /path/to/file/a /path/to/file/b
Adding a Mirror to a ZFS Storage Pool

The following command adds two mirrored disks to the pool tank, assuming the pool is already made up of two-way mirrors. The additional space is immediately available to any datasets within the pool.

# zpool add tank mirror da2 da3
Listing Available ZFS Storage Pools

The following command lists all available pools on the system.

# zpool list
NAME   SIZE  ALLOC   FREE   FRAG  EXPANDSZ    CAP  DEDUP  HEALTH  ALTROOT
pool  2.70T   473G  2.24T    33%         -    17%  1.00x  ONLINE  -
test  1.98G  89.5K  1.98G    48%         -     0%  1.00x  ONLINE  -
Listing All Properties for a Pool

The following command lists all the properties for a pool.

# zpool get all pool
pool  size           2.70T       -
pool  capacity       17%         -
pool  altroot        -           default
pool  health         ONLINE      -
pool  guid           2501120270416322443  default
pool  version        28          default
pool  bootfs         pool/root   local
pool  delegation     on          default
pool  autoreplace    off         default
pool  cachefile      -           default
pool  failmode       wait        default
pool  listsnapshots  off         default
pool  autoexpand     off         default
pool  dedupditto     0           default
pool  dedupratio     1.00x       -
pool  free           2.24T       -
pool  allocated      473G        -
pool  readonly       off         -
Destroying a ZFS Storage Pool

The following command destroys the pool "tank" and any datasets contained within.

# zpool destroy -f tank
Exporting a ZFS Storage Pool

The following command exports the devices in pool tank so that they can be relocated or later imported.

# zpool export tank
Importing a ZFS Storage Pool

The following command displays available pools, and then imports the pool "tank" for use on the system.

The results from this command are similar to the following:

# zpool import

  pool: tank
    id: 15451357997522795478
 state: ONLINE
action: The pool can be imported using its name or numeric identifier.
config:

        tank        ONLINE
          mirror    ONLINE
               da0  ONLINE
               da1  ONLINE
Upgrading All ZFS Storage Pools to the Current Version

The following command upgrades all ZFS Storage pools to the current version of the software.

# zpool upgrade -a
This system is currently running ZFS pool version 28.
Managing Hot Spares

The following command creates a new pool with an available hot spare:

# zpool create tank mirror da0 da1 spare da2

If one of the disks were to fail, the pool would be reduced to the degraded state. The failed device can be replaced using the following command:

# zpool replace tank da0 da2

Once the data has been resilvered, the spare is automatically removed and is made available should another device fails. The hot spare can be permanently removed from the pool using the following command:

# zpool remove tank da2
Creating a ZFS Pool with Mirrored Separate Intent Logs

The following command creates a ZFS storage pool consisting of two, two-way mirrors and mirrored log devices:

# zpool create pool mirror da0 da1 mirror da2 da3 log mirror da4 da5
Adding Cache Devices to a ZFS Pool

The following command adds two disks for use as cache devices to a ZFS storage pool:

# zpool add pool cache da2 da3

Once added, the cache devices gradually fill with content from main memory. Depending on the size of your cache devices, it could take over an hour for them to fill. Capacity and reads can be monitored using the iostat subcommand as follows:

# zpool iostat -v pool 5
Displaying expanded space on a device

The following command dipslays the detailed information for the pool. This pool is comprised of a single raidz vdev where one of its devices increased its capacity by 10GB. In this example, the pool will not be able to utilized this extra capacity until all the devices under the raidz vdev have been expanded.

# zpool list -v data
NAME       SIZE  ALLOC   FREE   FRAG  EXPANDSZ    CAP  DEDUP  HEALTH  ALTROOT
data      23.9G  14.6G  9.30G    48%         -    61%  1.00x  ONLINE  -
  raidz1  23.9G  14.6G  9.30G    48%         -
    ada0      -      -      -      -         -
    ada1      -      -      -      -       10G
    ada2      -      -      -      -         -
Removing a Mirrored top-level (Log or Data) Device

The following commands remove the mirrored log device mirror-2 and mirrored top-level data device mirror-1.

Given this configuration:

   pool: tank
  state: ONLINE
  scrub: none requested
 config:

         NAME        STATE     READ WRITE CKSUM
         tank        ONLINE       0     0     0
           mirror-0  ONLINE       0     0     0
                da0  ONLINE       0     0     0
                da1  ONLINE       0     0     0
           mirror-1  ONLINE       0     0     0
                da2  ONLINE       0     0     0
                da3  ONLINE       0     0     0
         logs
           mirror-2  ONLINE       0     0     0
                da4  ONLINE       0     0     0
                da5  ONLINE       0     0     0

The command to remove the mirrored log mirror-2 is:

# zpool remove tank mirror-2

The command to remove the mirrored data mirror-1 is:

# zpool remove tank mirror-1
Recovering a Faulted ZFS Pool

If a pool is faulted but recoverable, a message indicating this state is provided by "zpool status" if the pool was cached (see the -c cachefile argument above), or as part of the error output from a failed "zpool import" of the pool.

Recover a cached pool with the "zpool clear" command:

# zpool clear -F data
Pool data returned to its state as of Tue Sep 08 13:23:35 2009.
Discarded approximately 29 seconds of transactions.

If the pool configuration was not cached, use "zpool import" with the recovery mode flag:

# zpool import -F data
Pool data returned to its state as of Tue Sep 08 13:23:35 2009.
Discarded approximately 29 seconds of transactions.

zpool-features(7), zfs(8), zfsd(8)

This manual page is a mdoc(7) reimplementation of the OpenSolaris manual page , modified and customized for FreeBSD and licensed under the Common Development and Distribution License (CDDL).

The mdoc(7) implementation of this manual page was initially written by Martin Matuska ⟨mm@FreeBSD.org⟩.

April 27, 2018 FreeBSD-12.0