zpool-features - ZFS pool feature descriptions
ZFS pool on-disk format versions are specified via "features" which
replace the old on-disk format numbers (the last supported on-disk format
number is 28). To enable a feature on a pool use the
upgrade subcommand
of the zpool(8) command, or set the
feature@feature_name
property to
enabled. Please also see the
"Compatibility feature
sets" section for information on how sets of features may be enabled
together.
The pool format does not affect file system version compatibility or the ability
to send file systems between pools.
Since most features can be enabled independently of each other the on-disk
format of the pool is specified by the set of all features marked as
active on the pool. If the pool was created by another software version
this set may include unsupported features.
Every feature has a GUID of the form
com.example:feature_name. The
reversed DNS name ensures that the feature's GUID is unique across all ZFS
implementations. When unsupported features are encountered on a pool they will
be identified by their GUIDs. Refer to the documentation for the ZFS
implementation that created the pool for information about those features.
Each supported feature also has a short name. By convention a feature's short
name is the portion of its GUID which follows the ':' (e.g.
com.example:feature_name would have the short name
feature_name), however a feature's short name may differ across ZFS
implementations if following the convention would result in name conflicts.
Features can be in one of three states:
active
This feature's on-disk format changes are in effect on
the pool. Support for this feature is required to import the pool in
read-write mode. If this feature is not read-only compatible, support is also
required to import the pool in read-only mode (see "Read-only
compatibility").
enabled
An administrator has marked this feature as enabled on
the pool, but the feature's on-disk format changes have not been made yet. The
pool can still be imported by software that does not support this feature, but
changes may be made to the on-disk format at any time which will move the
feature to the active state. Some features may support returning to the
enabled state after becoming active. See feature-specific
documentation for details.
disabled
This feature's on-disk format changes have not been made
and will not be made unless an administrator moves the feature to the
enabled state. Features cannot be disabled once they have been
enabled.
The state of supported features is exposed through pool properties of the form
feature@short_name.
Some features may make on-disk format changes that do not interfere with other
software's ability to read from the pool. These features are referred to as
"read-only compatible". If all unsupported features on a pool are
read-only compatible, the pool can be imported in read-only mode by setting
the
readonly property during import (see zpool(8) for details on
importing pools).
For each unsupported feature enabled on an imported pool a pool property named
unsupported@feature_name will indicate why the import was allowed
despite the unsupported feature. Possible values for this property are:
inactive
The feature is in the enabled state and therefore
the pool's on-disk format is still compatible with software that does not
support this feature.
readonly
The feature is read-only compatible and the pool has been
imported in read-only mode.
Some features depend on other features being enabled in order to function
properly. Enabling a feature will automatically enable any features it depends
on.
It is sometimes necessary for a pool to maintain compatibility with a specific
on-disk format, by enabling and disabling particular features. The
compatibility feature facilitates this by allowing feature sets to be
read from text files. When set to
off (the default); compatibility
feature sets are disabled (ie: all features are enabled); when set to
legacy; no features are enabled. When set to a comma-separated list of
filenames (each filename may either be an absolute path, or relative to
/etc/zfs/compatibility.d or
/usr/share/zfs/compatibility.d) the
lists of requested features are read from those files, separated by whitespace
and/or commas. Only features present in all files are enabled.
Simple sanity checks are applied to the files; they must be between 1 and 16,384
bytes in size, and must end with a newline character.
The requested features are applied when a pool is created using
zpool create
-o compatibility=... and controls which features are enabled when using
zpool upgrade.
zpool status will not show a warning about
disabled features which are not part of the requested feature set.
By convention, compatibility files in
/usr/share/zfs/compatibility.d are
provided by the distribution package, and include feature sets supported by
important versions of popular distribtions, and feature sets commonly
supported at the start of each year. Compatibility files in
/etc/zfs/compatibility.d, if present, will take precedence over files
with the same name in
/usr/share/zfs/compatibility.d.
Compatibility files may include comments; any text from
# to the end of
the line is ignored.
Example:
# cat /usr/share/zfs/compatibility.d/grub2
# Features which are supported by GRUB2
async_destroy
bookmarks
embedded_data
empty_bpobj
enabled_txg
extensible_dataset
filesystem_limits
hole_birth
large_blocks
lz4_compress
spacemap_histogram
# zpool create -o compatibility=grub2 bootpool vdev
See
zpool-create(8) and
zpool-upgrade(8) for more information on
how these commands are affected by feature sets.
The following features are supported on this system:
allocation_classes
| GUID |
org.zfsonlinux:allocation_classes |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This feature enables support for separate allocation classes.
This feature becomes
active when a dedicated allocation class vdev (dedup
or special) is created with the
zpool create or
zpool add
subcommands. With device removal, it can be returned to the
enabled
state if all the dedicated allocation class vdevs are removed.
async_destroy
| GUID |
com.delphix:async_destroy |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
Destroying a file system requires traversing all of its data in order to return
its used space to the pool. Without
async_destroy the file system is
not fully removed until all space has been reclaimed. If the destroy operation
is interrupted by a reboot or power outage the next attempt to open the pool
will need to complete the destroy operation synchronously.
When
async_destroy is enabled the file system's data will be reclaimed by
a background process, allowing the destroy operation to complete without
traversing the entire file system. The background process is able to resume
interrupted destroys after the pool has been opened, eliminating the need to
finish interrupted destroys as part of the open operation. The amount of space
remaining to be reclaimed by the background process is available through the
freeing property.
This feature is only
active while
freeing is non-zero.
bookmarks
| GUID |
com.delphix:bookmarks |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
extensible_dataset |
This feature enables use of the
zfs bookmark subcommand.
This feature is
active while any bookmarks exist in the pool. All
bookmarks in the pool can be listed by running
zfs list -t bookmark -r
poolname.
bookmark_v2
| GUID |
com.datto:bookmark_v2 |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
bookmark, extensible_dataset |
This feature enables the creation and management of larger bookmarks which are
needed for other features in ZFS.
This feature becomes
active when a v2 bookmark is created and will be
returned to the
enabled state when all v2 bookmarks are
destroyed.
bookmark_written
| GUID |
com.delphix:bookmark_written |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
bookmark, extensible_dataset, bookmark_v2 |
This feature enables additional bookmark accounting fields, enabling the
written#<bookmark> property (space written since a bookmark) and
estimates of send stream sizes for incrementals from bookmarks.
This feature becomes
active when a bookmark is created and will be
returned to the
enabled state when all bookmarks with these fields are
destroyed.
device_rebuild
| GUID |
org.openzfs:device_rebuild |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This feature enables the ability for the
zpool attach and
zpool
replace subcommands to perform sequential reconstruction (instead of
healing reconstruction) when resilvering.
Sequential reconstruction resilvers a device in LBA order without immediately
verifying the checksums. Once complete a scrub is started which then verifies
the checksums. This approach allows full redundancy to be restored to the pool
in the minimum amount of time. This two phase approach will take longer than a
healing resilver when the time to verify the checksums is included. However,
unless there is additional pool damage no checksum errors should be reported
by the scrub. This feature is incompatible with raidz configurations.
This feature becomes
active while a sequential resilver is in progress,
and returns to
enabled when the resilver completes.
device_removal
| GUID |
com.delphix:device_removal |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
none |
This feature enables the
zpool remove subcommand to remove top-level
vdevs, evacuating them to reduce the total size of the pool.
This feature becomes
active when the
zpool remove subcommand is
used on a top-level vdev, and will never return to being
enabled.
draid
| GUID |
org.openzfs:draid |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
none |
This feature enables use of the
draid vdev type. dRAID is a variant of
raidz which provides integrated distributed hot spares that allow faster
resilvering while retaining the benefits of raidz. Data, parity, and spare
space are organized in redundancy groups and distributed evenly over all of
the devices.
This feature becomes
active when creating a pool which uses the
draid vdev type, or when adding a new
draid vdev to an existing
pool.
edonr
| GUID |
org.illumos:edonr |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
extensible_dataset |
This feature enables the use of the Edon-R hash algorithm for checksum,
including for nopwrite (if compression is also enabled, an overwrite of a
block whose checksum matches the data being written will be ignored). In an
abundance of caution, Edon-R requires verification when used with dedup:
zfs set dedup=edonr,verify. See
zfs(8).
Edon-R is a very high-performance hash algorithm that was part of the NIST SHA-3
competition. It provides extremely high hash performance (over 350% faster
than SHA-256), but was not selected because of its unsuitability as a general
purpose secure hash algorithm. This implementation utilizes the new salted
checksumming functionality in ZFS, which means that the checksum is pre-seeded
with a secret 256-bit random key (stored on the pool) before being fed the
data block to be checksummed. Thus the produced checksums are unique to a
given pool.
When the
edonr feature is set to
enabled, the administrator can
turn on the
edonr checksum on any dataset using the
zfs set
checksum=edonr. See zfs(8). This feature becomes
active once a
checksum property has been set to
edonr, and will return to
being
enabled once all filesystems that have ever had their checksum
set to
edonr are destroyed.
FreeBSD does not support the
edonr feature.
embedded_data
| GUID |
com.delphix:embedded_data |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
none |
This feature improves the performance and compression ratio of
highly-compressible blocks. Blocks whose contents can compress to 112 bytes or
smaller can take advantage of this feature.
When this feature is enabled, the contents of highly-compressible blocks are
stored in the block "pointer" itself (a misnomer in this case, as it
contains the compressed data, rather than a pointer to its location on disk).
Thus the space of the block (one sector, typically 512 bytes or 4KB) is saved,
and no additional i/o is needed to read and write the data block.
This feature becomes
active as soon as it is enabled and will never
return to being
enabled.
empty_bpobj
| GUID |
com.delphix:empty_bpobj |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This feature increases the performance of creating and using a large number of
snapshots of a single filesystem or volume, and also reduces the disk space
required.
When there are many snapshots, each snapshot uses many Block Pointer Objects
(bpobj's) to track blocks associated with that snapshot. However, in common
use cases, most of these bpobj's are empty. This feature allows us to create
each bpobj on-demand, thus eliminating the empty bpobjs.
This feature is
active while there are any filesystems, volumes, or
snapshots which were created after enabling this feature.
enabled_txg
| GUID |
com.delphix:enabled_txg |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
Once this feature is enabled ZFS records the transaction group number in which
new features are enabled. This has no user-visible impact, but other features
may depend on this feature.
This feature becomes
active as soon as it is enabled and will never
return to being
enabled.
encryption
| GUID |
com.datto:encryption |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
bookmark_v2, extensible_dataset |
This feature enables the creation and management of natively encrypted datasets.
This feature becomes
active when an encrypted dataset is created and will
be returned to the
enabled state when all datasets that use this
feature are destroyed.
extensible_dataset
| GUID |
com.delphix:extensible_dataset |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
none |
This feature allows more flexible use of internal ZFS data structures, and
exists for other features to depend on.
This feature will be
active when the first dependent feature uses it, and
will be returned to the
enabled state when all datasets that use this
feature are destroyed.
filesystem_limits
| GUID |
com.joyent:filesystem_limits |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
extensible_dataset |
This feature enables filesystem and snapshot limits. These limits can be used to
control how many filesystems and/or snapshots can be created at the point in
the tree on which the limits are set.
This feature is
active once either of the limit properties has been set
on a dataset. Once activated the feature is never deactivated.
hole_birth
| GUID |
com.delphix:hole_birth |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
enabled_txg |
This feature has/had bugs, the result of which is that, if you do a
zfs send
-i (or
-R, since it uses
-i) from an affected dataset, the
receiver will not see any checksum or other errors, but the resulting
destination snapshot will not match the source. Its use by
zfs send -i
has been disabled by default. See the
send_holes_without_birth_time
module parameter in zfs-module-parameters(5).
This feature improves performance of incremental sends (
zfs send -i) and
receives for objects with many holes. The most common case of hole-filled
objects is zvols.
An incremental send stream from snapshot
A to snapshot
B contains
information about every block that changed between
A and
B.
Blocks which did not change between those snapshots can be identified and
omitted from the stream using a piece of metadata called the 'block birth
time', but birth times are not recorded for holes (blocks filled only with
zeroes). Since holes created after
A cannot be distinguished from holes
created before
A, information about every hole in the entire filesystem
or zvol is included in the send stream.
For workloads where holes are rare this is not a problem. However, when
incrementally replicating filesystems or zvols with many holes (for example a
zvol formatted with another filesystem) a lot of time will be spent sending
and receiving unnecessary information about holes that already exist on the
receiving side.
Once the
hole_birth feature has been enabled the block birth times of all
new holes will be recorded. Incremental sends between snapshots created after
this feature is enabled will use this new metadata to avoid sending
information about holes that already exist on the receiving side.
This feature becomes
active as soon as it is enabled and will never
return to being
enabled.
large_blocks
| GUID |
org.open-zfs:large_blocks |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
extensible_dataset |
The
large_block feature allows the record size on a dataset to be set
larger than 128KB.
This feature becomes
active once a dataset contains a file with a block
size larger than 128KB, and will return to being
enabled once all
filesystems that have ever had their recordsize larger than 128KB are
destroyed.
large_dnode
| GUID |
org.zfsonlinux:large_dnode |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
extensible_dataset |
The
large_dnode feature allows the size of dnodes in a dataset to be set
larger than 512B.
This feature becomes
active once a dataset contains an object with a
dnode larger than 512B, which occurs as a result of setting the
dnodesize dataset property to a value other than
legacy. The
feature will return to being
enabled once all filesystems that have
ever contained a dnode larger than 512B are destroyed. Large dnodes allow more
data to be stored in the bonus buffer, thus potentially improving performance
by avoiding the use of spill blocks.
livelist
| GUID |
com.delphix:livelist |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This feature allows clones to be deleted faster than the traditional method when
a large number of random/sparse writes have been made to the clone. All blocks
allocated and freed after a clone is created are tracked by the the clone's
livelist which is referenced during the deletion of the clone. The feature is
activated when a clone is created and remains active until all clones have
been destroyed.
log_spacemap
| GUID |
com.delphix:log_spacemap |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
com.delphix:spacemap_v2 |
This feature improves performance for heavily-fragmented pools, especially when
workloads are heavy in random-writes. It does so by logging all the metaslab
changes on a single spacemap every TXG instead of scattering multiple writes
to all the metaslab spacemaps.
This feature becomes
active as soon as it is enabled and will never
return to being
enabled.
lz4_compress
| GUID |
org.illumos:lz4_compress |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
none |
lz4 is a high-performance real-time compression algorithm that features
significantly faster compression and decompression as well as a higher
compression ratio than the older
lzjb compression. Typically,
lz4 compression is approximately 50% faster on compressible data and
200% faster on incompressible data than
lzjb. It is also approximately
80% faster on decompression, while giving approximately 10% better compression
ratio.
When the
lz4_compress feature is set to
enabled, the administrator
can turn on
lz4 compression on any dataset on the pool using the zfs(8)
command. Please note that doing so will immediately activate the
lz4_compress feature on the underlying pool using the zfs(8) command.
Also, all newly written metadata will be compressed with
lz4 algorithm.
Since this feature is not read-only compatible, this operation will render the
pool unimportable on systems without support for the
lz4_compress
feature.
Booting off of
lz4-compressed root pools is supported.
This feature becomes
active as soon as it is enabled and will never
return to being
enabled.
multi_vdev_crash_dump
| GUID |
com.joyent:multi_vdev_crash_dump |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
none |
This feature allows a dump device to be configured with a pool comprised of
multiple vdevs. Those vdevs may be arranged in any mirrored or raidz
configuration.
When the
multi_vdev_crash_dump feature is set to
enabled, the
administrator can use the
dumpadm(1M) command to configure a dump
device on a pool comprised of multiple vdevs.
Under FreeBSD and Linux this feature is registered for compatibility but not
used. New pools created under FreeBSD and Linux will have the feature
enabled but will never transition to
active. This
functionality is not required in order to support crash dumps under FreeBSD
and Linux. Existing pools where this feature is
active can be
imported.
obsolete_counts
| GUID |
com.delphix:obsolete_counts |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
device_removal |
This feature is an enhancement of device_removal, which will over time reduce
the memory used to track removed devices. When indirect blocks are freed or
remapped, we note that their part of the indirect mapping is
"obsolete", i.e. no longer needed.
This feature becomes
active when the
zpool remove subcommand is
used on a top-level vdev, and will never return to being
enabled.
project_quota
| GUID |
org.zfsonlinux:project_quota |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
extensible_dataset |
This feature allows administrators to account the spaces and objects usage
information against the project identifier (ID).
The project ID is new object-based attribute. When upgrading an existing
filesystem, object without project ID attribute will be assigned a zero
project ID. After this feature is enabled, newly created object will inherit
its parent directory's project ID if the parent inherit flag is set (via
chattr +/-P or
zfs project [-s|-C]). Otherwise, the new object's
project ID will be set as zero. An object's project ID can be changed at
anytime by the owner (or privileged user) via
chattr -p $prjid or
zfs project -p $prjid.
This feature will become
active as soon as it is enabled and will never
return to being
disabled. Each filesystem will be upgraded
automatically when remounted or when new file is created under that
filesystem. The upgrade can also be triggered on filesystems via `zfs set
version=current <pool/fs>`. The upgrade process runs in the background
and may take a while to complete for the filesystems containing a large number
of files.
redaction_bookmarks
| GUID |
com.delphix:redaction_bookmarks |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
bookmarks, extensible_dataset |
This feature enables the use of the redacted zfs send. Redacted
zfs send
creates redaction bookmarks, which store the list of blocks redacted by the
send that created them. For more information about redacted send, see
zfs(8).
redacted_datasets
| GUID |
com.delphix:redacted_datasets |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
extensible_dataset |
This feature enables the receiving of redacted zfs send streams. Redacted zfs
send streams create redacted datasets when received. These datasets are
missing some of their blocks, and so cannot be safely mounted, and their
contents cannot be safely read. For more information about redacted receive,
see
zfs(8).
resilver_defer
| GUID |
com.datto:resilver_defer |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This feature allows zfs to postpone new resilvers if an existing one is already
in progress. Without this feature, any new resilvers will cause the currently
running one to be immediately restarted from the beginning.
This feature becomes
active once a resilver has been deferred, and
returns to being
enabled when the deferred resilver begins.
sha512
| GUID |
org.illumos:sha512 |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
extensible_dataset |
This feature enables the use of the SHA-512/256 truncated hash algorithm (FIPS
180-4) for checksum and dedup. The native 64-bit arithmetic of SHA-512
provides an approximate 50% performance boost over SHA-256 on 64-bit hardware
and is thus a good minimum-change replacement candidate for systems where hash
performance is important, but these systems cannot for whatever reason utilize
the faster
skein and
edonr algorithms.
When the
sha512 feature is set to
enabled, the administrator can
turn on the
sha512 checksum on any dataset using
zfs set
checksum=sha512. See zfs(8). This feature becomes
active once a
checksum property has been set to
sha512, and will return to
being
enabled once all filesystems that have ever had their checksum
set to
sha512 are destroyed.
skein
| GUID |
org.illumos:skein |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
extensible_dataset |
This feature enables the use of the Skein hash algorithm for checksum and dedup.
Skein is a high-performance secure hash algorithm that was a finalist in the
NIST SHA-3 competition. It provides a very high security margin and high
performance on 64-bit hardware (80% faster than SHA-256). This implementation
also utilizes the new salted checksumming functionality in ZFS, which means
that the checksum is pre-seeded with a secret 256-bit random key (stored on
the pool) before being fed the data block to be checksummed. Thus the produced
checksums are unique to a given pool, preventing hash collision attacks on
systems with dedup.
When the
skein feature is set to
enabled, the administrator can
turn on the
skein checksum on any dataset using
zfs set
checksum=skein. See zfs(8). This feature becomes
active once a
checksum property has been set to
skein, and will return to
being
enabled once all filesystems that have ever had their checksum
set to
skein are destroyed.
spacemap_histogram
| GUID |
com.delphix:spacemap_histogram |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This features allows ZFS to maintain more information about how free space is
organized within the pool. If this feature is
enabled, ZFS will set
this feature to
active when a new space map object is created or an
existing space map is upgraded to the new format. Once the feature is
active, it will remain in that state until the pool is destroyed.
spacemap_v2
| GUID |
com.delphix:spacemap_v2 |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This feature enables the use of the new space map encoding which consists of two
words (instead of one) whenever it is advantageous. The new encoding allows
space maps to represent large regions of space more efficiently on-disk while
also increasing their maximum addressable offset.
This feature becomes
active once it is
enabled, and never returns
back to being
enabled.
userobj_accounting
| GUID |
org.zfsonlinux:userobj_accounting |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
extensible_dataset |
This feature allows administrators to account the object usage information by
user and group.
This feature becomes
active as soon as it is enabled and will never
return to being
enabled. Each filesystem will be upgraded automatically
when remounted, or when new files are created under that filesystem. The
upgrade can also be started manually on filesystems by running `zfs set
version=current <pool/fs>`. The upgrade process runs in the background
and may take a while to complete for filesystems containing a large number of
files.
zpool_checkpoint
| GUID |
com.delphix:zpool_checkpoint |
| READ-ONLY COMPATIBLE |
yes |
| DEPENDENCIES |
none |
This feature enables the
zpool checkpoint subcommand that can checkpoint
the state of the pool at the time it was issued and later rewind back to it or
discard it.
This feature becomes
active when the
zpool checkpoint subcommand
is used to checkpoint the pool. The feature will only return back to being
enabled when the pool is rewound or the checkpoint has been
discarded.
zstd_compress
| GUID |
org.freebsd:zstd_compress |
| READ-ONLY COMPATIBLE |
no |
| DEPENDENCIES |
extensible_dataset |
zstd is a high-performance compression algorithm that features a
combination of high compression ratios and high speed. Compared to
gzip,
zstd offers slighty better compression at much higher
speeds. Compared to
lz4,
zstd offers much better compression
while being only modestly slower. Typically,
zstd compression speed
ranges from 250 to 500 MB/s per thread and decompression speed is over 1 GB/s
per thread.
When the
zstd feature is set to
enabled, the administrator can
turn on
zstd compression of any dataset by running `zfs set
compress=zstd <pool/fs>`.
This feature becomes
active once a
compress property has been set
to
zstd, and will return to being
enabled once all filesystems
that have ever had their compress property set to
zstd are destroyed.
Booting off of
zstd-compressed root pools is not yet supported.
zpool(8)