827 lines
25 KiB
Groff
827 lines
25 KiB
Groff
'\" te
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.\" Copyright (c) 2013, 2017 by Delphix. All rights reserved.
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.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
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.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
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.\" The contents of this file are subject to the terms of the Common Development
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.\" and Distribution License (the "License"). You may not use this file except
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.\" in compliance with the License. You can obtain a copy of the license at
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.\" usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.
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.\"
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.\" See the License for the specific language governing permissions and
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.\" limitations under the License. When distributing Covered Code, include this
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.\" CDDL HEADER in each file and include the License file at
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.\" usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this
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.\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your
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.\" own identifying information:
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.\" Portions Copyright [yyyy] [name of copyright owner]
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.TH ZPOOL-FEATURES 5 "Jun 8, 2018"
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.SH NAME
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zpool\-features \- ZFS pool feature descriptions
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.SH DESCRIPTION
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.sp
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.LP
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ZFS pool on\-disk format versions are specified via "features" which replace
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the old on\-disk format numbers (the last supported on\-disk format number is
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28). To enable a feature on a pool use the \fBupgrade\fR subcommand of the
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zpool(8) command, or set the \fBfeature@\fR\fIfeature_name\fR property
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to \fBenabled\fR.
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.sp
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.LP
|
|
The pool format does not affect file system version compatibility or the ability
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to send file systems between pools.
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.sp
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.LP
|
|
Since most features can be enabled independently of each other the on\-disk
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format of the pool is specified by the set of all features marked as
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\fBactive\fR on the pool. If the pool was created by another software version
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this set may include unsupported features.
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.SS "Identifying features"
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|
.sp
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|
.LP
|
|
Every feature has a GUID of the form \fIcom.example:feature_name\fR. The
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reverse DNS name ensures that the feature's GUID is unique across all ZFS
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implementations. When unsupported features are encountered on a pool they will
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be identified by their GUIDs. Refer to the documentation for the ZFS
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implementation that created the pool for information about those features.
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|
.sp
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.LP
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|
Each supported feature also has a short name. By convention a feature's short
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name is the portion of its GUID which follows the ':' (e.g.
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|
\fIcom.example:feature_name\fR would have the short name \fIfeature_name\fR),
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|
however a feature's short name may differ across ZFS implementations if
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following the convention would result in name conflicts.
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.SS "Feature states"
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|
.sp
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|
.LP
|
|
Features can be in one of three states:
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.sp
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.ne 2
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.na
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|
\fBactive\fR
|
|
.ad
|
|
.RS 12n
|
|
This feature's on\-disk format changes are in effect on the pool. Support for
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this feature is required to import the pool in read\-write mode. If this
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feature is not read-only compatible, support is also required to import the pool
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in read\-only mode (see "Read\-only compatibility").
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.RE
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|
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.sp
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.ne 2
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.na
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\fBenabled\fR
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|
.ad
|
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.RS 12n
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|
An administrator has marked this feature as enabled on the pool, but the
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feature's on\-disk format changes have not been made yet. The pool can still be
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imported by software that does not support this feature, but changes may be made
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to the on\-disk format at any time which will move the feature to the
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\fBactive\fR state. Some features may support returning to the \fBenabled\fR
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|
state after becoming \fBactive\fR. See feature\-specific documentation for
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|
details.
|
|
.RE
|
|
|
|
.sp
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.ne 2
|
|
.na
|
|
\fBdisabled\fR
|
|
.ad
|
|
.RS 12n
|
|
This feature's on\-disk format changes have not been made and will not be made
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|
unless an administrator moves the feature to the \fBenabled\fR state. Features
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|
cannot be disabled once they have been enabled.
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.RE
|
|
|
|
.sp
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|
.LP
|
|
The state of supported features is exposed through pool properties of the form
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\fIfeature@short_name\fR.
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.SS "Read\-only compatibility"
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|
.sp
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.LP
|
|
Some features may make on\-disk format changes that do not interfere with other
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|
software's ability to read from the pool. These features are referred to as
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"read\-only compatible". If all unsupported features on a pool are read\-only
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compatible, the pool can be imported in read\-only mode by setting the
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\fBreadonly\fR property during import (see zpool(8) for details on
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importing pools).
|
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.SS "Unsupported features"
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|
.sp
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.LP
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|
For each unsupported feature enabled on an imported pool a pool property
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|
named \fIunsupported@feature_name\fR will indicate why the import was allowed
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|
despite the unsupported feature. Possible values for this property are:
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|
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.sp
|
|
.ne 2
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.na
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|
\fBinactive\fR
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|
.ad
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.RS 12n
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|
The feature is in the \fBenabled\fR state and therefore the pool's on\-disk
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|
format is still compatible with software that does not support this feature.
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.RE
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|
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.sp
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.ne 2
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.na
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|
\fBreadonly\fR
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|
.ad
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|
.RS 12n
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|
The feature is read\-only compatible and the pool has been imported in
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|
read\-only mode.
|
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.RE
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|
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.SS "Feature dependencies"
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|
.sp
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.LP
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|
Some features depend on other features being enabled in order to function
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properly. Enabling a feature will automatically enable any features it
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depends on.
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.SH FEATURES
|
|
.sp
|
|
.LP
|
|
The following features are supported on this system:
|
|
|
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.sp
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|
.ne 2
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.na
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|
\fBallocation_classes\fR
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|
.ad
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.RS 4n
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.TS
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|
l l .
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GUID org.zfsonlinux:allocation_classes
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|
READ\-ONLY COMPATIBLE yes
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DEPENDENCIES none
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.TE
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|
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This feature enables support for separate allocation classes.
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This feature becomes \fBactive\fR when a dedicated allocation class vdev
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(dedup or special) is created with the \fBzpool create\fR or \fBzpool add\fR
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subcommands. With device removal, it can be returned to the \fBenabled\fR
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state if all the dedicated allocation class vdevs are removed.
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.RE
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.sp
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.ne 2
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.na
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|
\fBasync_destroy\fR
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|
.ad
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.RS 4n
|
|
.TS
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|
l l .
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|
GUID com.delphix:async_destroy
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|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES none
|
|
.TE
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|
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|
Destroying a file system requires traversing all of its data in order to
|
|
return its used space to the pool. Without \fBasync_destroy\fR the file system
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|
is not fully removed until all space has been reclaimed. If the destroy
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|
operation is interrupted by a reboot or power outage the next attempt to open
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the pool will need to complete the destroy operation synchronously.
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When \fBasync_destroy\fR 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
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|
of space remaining to be reclaimed by the background process is available
|
|
through the \fBfreeing\fR property.
|
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|
This feature is only \fBactive\fR while \fBfreeing\fR is non\-zero.
|
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.RE
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|
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|
.sp
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|
.ne 2
|
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.na
|
|
\fBbookmarks\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:bookmarks
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|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
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|
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|
This feature enables use of the \fBzfs bookmark\fR subcommand.
|
|
|
|
This feature is \fBactive\fR while any bookmarks exist in the pool.
|
|
All bookmarks in the pool can be listed by running
|
|
\fBzfs list -t bookmark -r \fIpoolname\fR\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBbookmark_v2\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.datto:bookmark_v2
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES bookmark, extensible_dataset
|
|
.TE
|
|
|
|
This feature enables the creation and management of larger bookmarks which are
|
|
needed for other features in ZFS.
|
|
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|
This feature becomes \fBactive\fR when a v2 bookmark is created and will be
|
|
returned to the \fBenabled\fR state when all v2 bookmarks are destroyed.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBdevice_removal\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:device_removal
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
This feature enables the \fBzpool remove\fR subcommand to remove top-level
|
|
vdevs, evacuating them to reduce the total size of the pool.
|
|
|
|
This feature becomes \fBactive\fR when the \fBzpool remove\fR subcommand is used
|
|
on a top-level vdev, and will never return to being \fBenabled\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBedonr\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.illumos:edonr
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
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: \fBzfs set dedup=edonr,verify\fR. See \fBzfs\fR(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 \fBedonr\fR feature is set to \fBenabled\fR, the administrator
|
|
can turn on the \fBedonr\fR checksum on any dataset using the
|
|
\fBzfs set checksum=edonr\fR. See zfs(8). This feature becomes
|
|
\fBactive\fR once a \fBchecksum\fR property has been set to \fBedonr\fR,
|
|
and will return to being \fBenabled\fR once all filesystems that have
|
|
ever had their checksum set to \fBedonr\fR are destroyed.
|
|
|
|
The \fBedonr\fR feature is not supported by GRUB and must not be used on
|
|
the pool if GRUB needs to access the pool (e.g. for /boot).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBembedded_data\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:embedded_data
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
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 \fBactive\fR as soon as it is enabled and will
|
|
never return to being \fBenabled\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBempty_bpobj\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:empty_bpobj
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
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 \fBactive\fR while there are any filesystems, volumes,
|
|
or snapshots which were created after enabling this feature.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBenabled_txg\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:enabled_txg
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
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 \fBactive\fR as soon as it is enabled and will
|
|
never return to being \fBenabled\fB.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBencryption\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.datto:encryption
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES bookmark_v2, extensible_dataset
|
|
.TE
|
|
|
|
This feature enables the creation and management of natively encrypted datasets.
|
|
|
|
This feature becomes \fBactive\fR when an encrypted dataset is created and will
|
|
be returned to the \fBenabled\fR state when all datasets that use this feature
|
|
are destroyed.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBextensible_dataset\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:extensible_dataset
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
This feature allows more flexible use of internal ZFS data structures,
|
|
and exists for other features to depend on.
|
|
|
|
This feature will be \fBactive\fR when the first dependent feature uses it,
|
|
and will be returned to the \fBenabled\fR state when all datasets that use
|
|
this feature are destroyed.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBfilesystem_limits\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.joyent:filesystem_limits
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
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 \fBactive\fR once either of the limit properties has been
|
|
set on a dataset. Once activated the feature is never deactivated.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBhole_birth\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:hole_birth
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES enabled_txg
|
|
.TE
|
|
|
|
This feature has/had bugs, the result of which is that, if you do a
|
|
\fBzfs send -i\fR (or \fB-R\fR, since it uses \fB-i\fR) 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
|
|
\fBzfs send -i\fR has been disabled by default. See the
|
|
\fBsend_holes_without_birth_time\fR module parameter in
|
|
zfs-module-parameters(5).
|
|
|
|
This feature improves performance of incremental sends (\fBzfs send -i\fR)
|
|
and receives for objects with many holes. The most common case of
|
|
hole-filled objects is zvols.
|
|
|
|
An incremental send stream from snapshot \fBA\fR to snapshot \fBB\fR
|
|
contains information about every block that changed between \fBA\fR and
|
|
\fBB\fR. 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 \fBA\fR cannot be
|
|
distinguished from holes created before \fBA\fR, 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 \fBhole_birth\fR 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 \fBactive\fR as soon as it is enabled and will
|
|
never return to being \fBenabled\fB.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBlarge_blocks\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.open-zfs:large_blocks
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
The \fBlarge_block\fR feature allows the record size on a dataset to be
|
|
set larger than 128KB.
|
|
|
|
This feature becomes \fBactive\fR once a dataset contains a file with
|
|
a block size larger than 128KB, and will return to being \fBenabled\fR once all
|
|
filesystems that have ever had their recordsize larger than 128KB are destroyed.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBlarge_dnode\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.zfsonlinux:large_dnode
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
The \fBlarge_dnode\fR feature allows the size of dnodes in a dataset to be
|
|
set larger than 512B.
|
|
|
|
This feature becomes \fBactive\fR once a dataset contains an object with
|
|
a dnode larger than 512B, which occurs as a result of setting the
|
|
\fBdnodesize\fR dataset property to a value other than \fBlegacy\fR. The
|
|
feature will return to being \fBenabled\fR 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.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBlz4_compress\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.illumos:lz4_compress
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
\fBlz4\fR 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 \fBlzjb\fR compression.
|
|
Typically, \fBlz4\fR compression is approximately 50% faster on
|
|
compressible data and 200% faster on incompressible data than
|
|
\fBlzjb\fR. It is also approximately 80% faster on decompression, while
|
|
giving approximately 10% better compression ratio.
|
|
|
|
When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
|
|
administrator can turn on \fBlz4\fR compression on any dataset on the
|
|
pool using the zfs(8) command. Please note that doing so will
|
|
immediately activate the \fBlz4_compress\fR feature on the underlying
|
|
pool using the zfs(8) command. Also, all newly written metadata
|
|
will be compressed with \fBlz4\fR algorithm. Since this feature is not
|
|
read-only compatible, this operation will render the pool unimportable
|
|
on systems without support for the \fBlz4_compress\fR feature.
|
|
|
|
Booting off of \fBlz4\fR-compressed root pools is supported.
|
|
|
|
This feature becomes \fBactive\fR as soon as it is enabled and will
|
|
never return to being \fBenabled\fB.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBmulti_vdev_crash_dump\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.joyent:multi_vdev_crash_dump
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
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 \fBmulti_vdev_crash_dump\fR feature is set to \fBenabled\fR,
|
|
the administrator can use the \fBdumpadm\fR(1M) command to configure a
|
|
dump device on a pool comprised of multiple vdevs.
|
|
|
|
Under Linux this feature is registered for compatibility but not used.
|
|
New pools created under Linux will have the feature \fBenabled\fR but
|
|
will never transition to \fB\fBactive\fR. This functionality is not
|
|
required in order to support crash dumps under Linux. Existing pools
|
|
where this feature is \fB\fBactive\fR can be imported.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBobsolete_counts\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:obsolete_counts
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES device_removal
|
|
.TE
|
|
|
|
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 \fBactive\fR when the \fBzpool remove\fR subcommand is
|
|
used on a top-level vdev, and will never return to being \fBenabled\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBproject_quota\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.zfsonlinux:project_quota
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
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
|
|
\fBchattr +/-P\fR or \fBzfs project [-s|-C]\fR). 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 \fBchattr -p $prjid\fR or
|
|
\fBzfs project -p $prjid\fR.
|
|
|
|
This feature will become \fBactive\fR as soon as it is enabled and will never
|
|
return to being \fBdisabled\fR. 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.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBresilver_defer\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.datto:resilver_defer
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
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 \fBactive\fR once a resilver has been deferred, and
|
|
returns to being \fBenabled\fR when the deferred resilver begins.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBsha512\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.illumos:sha512
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
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 \fBskein\fR and
|
|
\fBedonr\fR algorithms.
|
|
|
|
When the \fBsha512\fR feature is set to \fBenabled\fR, the administrator
|
|
can turn on the \fBsha512\fR checksum on any dataset using
|
|
\fBzfs set checksum=sha512\fR. See zfs(8). This feature becomes
|
|
\fBactive\fR once a \fBchecksum\fR property has been set to \fBsha512\fR,
|
|
and will return to being \fBenabled\fR once all filesystems that have
|
|
ever had their checksum set to \fBsha512\fR are destroyed.
|
|
|
|
The \fBsha512\fR feature is not supported by GRUB and must not be used on
|
|
the pool if GRUB needs to access the pool (e.g. for /boot).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBskein\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.illumos:skein
|
|
READ\-ONLY COMPATIBLE no
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
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 \fBskein\fR feature is set to \fBenabled\fR, the administrator
|
|
can turn on the \fBskein\fR checksum on any dataset using
|
|
\fBzfs set checksum=skein\fR. See zfs(8). This feature becomes
|
|
\fBactive\fR once a \fBchecksum\fR property has been set to \fBskein\fR,
|
|
and will return to being \fBenabled\fR once all filesystems that have
|
|
ever had their checksum set to \fBskein\fR are destroyed.
|
|
|
|
The \fBskein\fR feature is not supported by GRUB and must not be used on
|
|
the pool if GRUB needs to access the pool (e.g. for /boot).
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBspacemap_histogram\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:spacemap_histogram
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
This features allows ZFS to maintain more information about how free space
|
|
is organized within the pool. If this feature is \fBenabled\fR, ZFS will
|
|
set this feature to \fBactive\fR when a new space map object is created or
|
|
an existing space map is upgraded to the new format. Once the feature is
|
|
\fBactive\fR, it will remain in that state until the pool is destroyed.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBspacemap_v2\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:spacemap_v2
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
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 \fBactive\fR once it is \fBenabled\fR, and never
|
|
returns back to being \fBenabled\fR.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBuserobj_accounting\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID org.zfsonlinux:userobj_accounting
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES extensible_dataset
|
|
.TE
|
|
|
|
This feature allows administrators to account the object usage information
|
|
by user and group.
|
|
|
|
This feature becomes \fBactive\fR as soon as it is enabled and will never
|
|
return to being \fBenabled\fR. 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.
|
|
.RE
|
|
|
|
.sp
|
|
.ne 2
|
|
.na
|
|
\fBzpool_checkpoint\fR
|
|
.ad
|
|
.RS 4n
|
|
.TS
|
|
l l .
|
|
GUID com.delphix:zpool_checkpoint
|
|
READ\-ONLY COMPATIBLE yes
|
|
DEPENDENCIES none
|
|
.TE
|
|
|
|
This feature enables the \fBzpool checkpoint\fR 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 \fBactive\fR when the \fBzpool checkpoint\fR subcommand
|
|
is used to checkpoint the pool.
|
|
The feature will only return back to being \fBenabled\fR when the pool
|
|
is rewound or the checkpoint has been discarded.
|
|
.RE
|
|
|
|
.SH "SEE ALSO"
|
|
zpool(8)
|