93cf20764a
4101 metaslab_debug should allow for fine-grained control
4102 space_maps should store more information about themselves
4103 space map object blocksize should be increased
4105 removing a mirrored log device results in a leaked object
4106 asynchronously load metaslab
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Sebastien Roy <seb@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Prior to this patch, space_maps were preferred solely based on the
amount of free space left in each. Unfortunately, this heuristic didn't
contain any information about the make-up of that free space, which
meant we could keep preferring and loading a highly fragmented space map
that wouldn't actually have enough contiguous space to satisfy the
allocation; then unloading that space_map and repeating the process.
This change modifies the space_map's to store additional information
about the contiguous space in the space_map, so that we can use this
information to make a better decision about which space_map to load.
This requires reallocating all space_map objects to increase their
bonus buffer size sizes enough to fit the new metadata.
The above feature can be enabled via a new feature flag introduced by
this change: com.delphix:spacemap_histogram
In addition to the above, this patch allows the space_map block size to
be increase. Currently the block size is set to be 4K in size, which has
certain implications including the following:
* 4K sector devices will not see any compression benefit
* large space_maps require more metadata on-disk
* large space_maps require more time to load (typically random reads)
Now the space_map block size can adjust as needed up to the maximum size
set via the space_map_max_blksz variable.
A bug was fixed which resulted in potentially leaking an object when
removing a mirrored log device. The previous logic for vdev_remove() did
not deal with removing top-level vdevs that are interior vdevs (i.e.
mirror) correctly. The problem would occur when removing a mirrored log
device, and result in the DTL space map object being leaked; because
top-level vdevs don't have DTL space map objects associated with them.
References:
https://www.illumos.org/issues/4101
https://www.illumos.org/issues/4102
https://www.illumos.org/issues/4103
https://www.illumos.org/issues/4105
https://www.illumos.org/issues/4106
https://github.com/illumos/illumos-gate/commit/0713e23
Porting notes:
A handful of kmem_alloc() calls were converted to kmem_zalloc(). Also,
the KM_PUSHPAGE and TQ_PUSHPAGE flags were used as necessary.
Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Prakash Surya <surya1@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2488
256 lines
8.4 KiB
Groff
256 lines
8.4 KiB
Groff
'\" te
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.\" Copyright (c) 2013 by Delphix. All rights reserved.
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.\" Copyright (c) 2013 by Saso Kiselkov. 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 "Aug 27, 2013"
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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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\fBzpool\fR(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
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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
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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
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Every feature has a guid of the form \fIcom.example:feature_name\fR. The reverse
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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
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|
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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\fB\fBactive\fR\fR
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.ad
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.RS 12n
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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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.sp
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.ne 2
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.na
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\fB\fBenabled\fR\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.
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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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\fBdisabled\fR
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.ad
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.RS 12n
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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
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.sp
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.LP
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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
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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 \fBzpool\fR(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_guid\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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.sp
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.ne 2
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.na
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\fB\fBinactive\fR\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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.sp
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.ne 2
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.na
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\fB\fBreadonly\fR\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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.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
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.sp
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.LP
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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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\fB\fBasync_destroy\fR\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 com.delphix:async_destroy
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READ\-ONLY COMPATIBLE yes
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DEPENDENCIES none
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.TE
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Destroying a file system requires traversing all of its data in order to
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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
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by a background process, allowing the destroy operation to complete without
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traversing the entire file system. The background process is able to resume
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interrupted destroys after the pool has been opened, eliminating the need
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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
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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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.sp
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.ne 2
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.na
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\fB\fBempty_bpobj\fR\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 com.delphix:empty_bpobj
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READ\-ONLY COMPATIBLE yes
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DEPENDENCIES none
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.TE
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This feature increases the performance of creating and using a large
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number of snapshots of a single filesystem or volume, and also reduces
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the disk space required.
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When there are many snapshots, each snapshot uses many Block Pointer
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Objects (bpobj's) to track blocks associated with that snapshot.
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However, in common use cases, most of these bpobj's are empty. This
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feature allows us to create each bpobj on-demand, thus eliminating the
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empty bpobjs.
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This feature is \fBactive\fR while there are any filesystems, volumes,
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or snapshots which were created after enabling this feature.
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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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\fB\fBlz4_compress\fR\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.illumos:lz4_compress
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READ\-ONLY COMPATIBLE no
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DEPENDENCIES none
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.TE
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\fBlz4\fR is a high-performance real-time compression algorithm that
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features significantly faster compression and decompression as well as a
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higher compression ratio than the older \fBlzjb\fR compression.
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Typically, \fBlz4\fR compression is approximately 50% faster on
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compressible data and 200% faster on incompressible data than
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\fBlzjb\fR. It is also approximately 80% faster on decompression, while
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giving approximately 10% better compression ratio.
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When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
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administrator can turn on \fBlz4\fR compression on any dataset on the
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pool using the \fBzfs\fR(8) command. Please note that doing so will
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immediately activate the \fBlz4_compress\fR feature on the underlying
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pool (even before any data is written). Since this feature is not
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read-only compatible, this operation will render the pool unimportable
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on systems without support for the \fBlz4_compress\fR feature. At the
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moment, this operation cannot be reversed. Booting off of
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\fBlz4\fR-compressed root pools is supported.
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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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\fB\fBspacemap_histogram\fR\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 com.delphix:spacemap_histogram
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READ\-ONLY COMPATIBLE yes
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DEPENDENCIES none
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.TE
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This features allows ZFS to maintain more information about how free space
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is organized within the pool. If this feature is \fBenabled\fR, ZFS will
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set this feature to \fBactive\fR when a new space map object is created or
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an existing space map is upgraded to the new format. Once the feature is
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\fBactive\fR, it will remain in that state until the pool is destroyed.
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.RE
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.SH "SEE ALSO"
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\fBzpool\fR(8)
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