1 '\" te 2 .\" Copyright (c) 2012 by Delphix. All rights reserved. 3 .\" The contents of this file are subject to the terms of the Common Development 4 .\" and Distribution License (the "License"). You may not use this file except 5 .\" in compliance with the License. You can obtain a copy of the license at 6 .\" usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. 7 .\" 8 .\" See the License for the specific language governing permissions and 9 .\" limitations under the License. When distributing Covered Code, include this 10 .\" CDDL HEADER in each file and include the License file at 11 .\" usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this 12 .\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your 13 .\" own identifying information: 14 .\" Portions Copyright [yyyy] [name of copyright owner] 15 .TH ZPOOL-FEATURES 5 "Mar 16, 2012" 16 .SH NAME 17 zpool\-features \- ZFS pool feature descriptions 18 .SH DESCRIPTION 19 .sp 20 .LP 21 ZFS pool on\-disk format versions are specified via "features" which replace 22 the old on\-disk format numbers (the last supported on\-disk format number is 23 28). To enable a feature on a pool use the \fBzpool\fR(1M) command to set 24 the \fBfeature@\fR\fIfeature_name\fR property to \fBenabled\fR. 25 .sp 26 .LP 27 The pool format does not affect file system version compatibility or the ability 28 to send file systems between pools. 29 .sp 30 .LP 31 Since most features can be enabled independently of each other the on\-disk 32 format of the pool is specified by the set of all features marked as 33 \fBactive\fR on the pool. If the pool was created by another software version 34 this set may include unsupported features. 35 .SS "Identifying features" 36 .sp 37 .LP 38 Every feature has a guid of the form \fIcom.example:feature_name\fR. The reverse 39 DNS name ensures that the feature's guid is unique across all ZFS 40 implementations. When unsupported features are encountered on a pool they will 41 be identified by their guids. Refer to the documentation for the ZFS 42 implementation that created the pool for information about those features. 43 .sp 44 .LP 45 Each supported feature also has a short name. By convention a feature's short 46 name is the portion of its guid which follows the ':' (e.g. 47 \fIcom.example:feature_name\fR would have the short name \fIfeature_name\fR), 48 however a feature's short name may differ across ZFS implementations if 49 following the convention would result in name conflicts. 50 .SS "Feature states" 51 .sp 52 .LP 53 Features can be in one of three states: 54 .sp 55 .ne 2 56 .na 57 \fB\fBactive\fR\fR 58 .ad 59 .RS 12n 60 This feature's on\-disk format changes are in effect on the pool. Support for 61 this feature is required to import the pool in read\-write mode. If this 62 feature is not read-only compatible, support is also required to import the pool 63 in read\-only mode (see "Read\-only compatibility"). 64 .RE 65 66 .sp 67 .ne 2 68 .na 69 \fB\fBenabled\fR\fR 70 .ad 71 .RS 12n 72 An administrator has marked this feature as enabled on the pool, but the 73 feature's on\-disk format changes have not been made yet. The pool can still be 74 imported by software that does not support this feature, but changes may be made 75 to the on\-disk format at any time which will move the feature to the 76 \fBactive\fR state. Some features may support returning to the \fBenabled\fR 77 state after becoming \fBactive\fR. See feature\-specific documentation for 78 details. 79 .RE 80 81 .sp 82 .ne 2 83 .na 84 \fBdisabled\fR 85 .ad 86 .RS 12n 87 This feature's on\-disk format changes have not been made and will not be made 88 unless an administrator moves the feature to the \fBenabled\fR state. Features 89 cannot be disabled once they have been enabled. 90 .RE 91 92 .sp 93 .LP 94 The state of supported features is exposed through pool properties of the form 95 \fIfeature@short_name\fR. 96 .SS "Read\-only compatibility" 97 .sp 98 .LP 99 Some features may make on\-disk format changes that do not interfere with other 100 software's ability to read from the pool. These features are referred to as 101 "read\-only compatible". If all unsupported features on a pool are read\-only 102 compatible, the pool can be imported in read\-only mode by setting the 103 \fBreadonly\fR property during import (see \fBzpool\fR(1M) for details on 104 importing pools). 105 .SS "Unsupported features" 106 .sp 107 .LP 108 For each unsupported feature enabled on an imported pool a pool property 109 named \fIunsupported@feature_guid\fR will indicate why the import was allowed 110 despite the unsupported feature. Possible values for this property are: 111 112 .sp 113 .ne 2 114 .na 115 \fB\fBinactive\fR\fR 116 .ad 117 .RS 12n 118 The feature is in the \fBenabled\fR state and therefore the pool's on\-disk 119 format is still compatible with software that does not support this feature. 120 .RE 121 122 .sp 123 .ne 2 124 .na 125 \fB\fBreadonly\fR\fR 126 .ad 127 .RS 12n 128 The feature is read\-only compatible and the pool has been imported in 129 read\-only mode. 130 .RE 131 132 .SS "Feature dependencies" 133 .sp 134 .LP 135 Some features depend on other features being enabled in order to function 136 properly. Enabling a feature will automatically enable any features it 137 depends on. 138 .SH FEATURES 139 .sp 140 .LP 141 The following features are supported on this system: 142 .sp 143 .ne 2 144 .na 145 \fB\fBasync_destroy\fR\fR 146 .ad 147 .RS 4n 148 .TS 149 l l . 150 GUID com.delphix:async_destroy 151 READ\-ONLY COMPATIBLE yes 152 DEPENDENCIES none 153 .TE 154 155 Destroying a file system requires traversing all of its data in order to 156 return its used space to the pool. Without \fBasync_destroy\fR the file system 157 is not fully removed until all space has been reclaimed. If the destroy 158 operation is interrupted by a reboot or power outage the next attempt to open 159 the pool will need to complete the destroy operation synchronously. 160 161 When \fBasync_destroy\fR is enabled the file system's data will be reclaimed 162 by a background process, allowing the destroy operation to complete without 163 traversing the entire file system. The background process is able to resume 164 interrupted destroys after the pool has been opened, eliminating the need 165 to finish interrupted destroys as part of the open operation. The amount 166 of space remaining to be reclaimed by the background process is available 167 through the \fBfreeing\fR property. 168 169 This feature is only \fBactive\fR while \fBfreeing\fR is non\-zero. 170 .RE 171 .SH "SEE ALSO" 172 \fBzpool\fR(1M)