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1 | '\" te | |
2 | .\" Copyright (c) 2013, 2017 by Delphix. All rights reserved. | |
3 | .\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved. | |
4 | .\" Copyright (c) 2014, Joyent, Inc. All rights reserved. | |
5 | .\" The contents of this file are subject to the terms of the Common Development | |
6 | .\" and Distribution License (the "License"). You may not use this file except | |
7 | .\" in compliance with the License. You can obtain a copy of the license at | |
8 | .\" usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. | |
9 | .\" | |
10 | .\" See the License for the specific language governing permissions and | |
11 | .\" limitations under the License. When distributing Covered Code, include this | |
12 | .\" CDDL HEADER in each file and include the License file at | |
13 | .\" usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this | |
14 | .\" CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your | |
15 | .\" own identifying information: | |
16 | .\" Portions Copyright [yyyy] [name of copyright owner] | |
17 | .TH ZPOOL-FEATURES 5 "Jun 8, 2018" | |
18 | .SH NAME | |
19 | zpool\-features \- ZFS pool feature descriptions | |
20 | .SH DESCRIPTION | |
21 | .sp | |
22 | .LP | |
23 | ZFS pool on\-disk format versions are specified via "features" which replace | |
24 | the old on\-disk format numbers (the last supported on\-disk format number is | |
25 | 28). To enable a feature on a pool use the \fBupgrade\fR subcommand of the | |
26 | \fBzpool\fR(8) command, or set the \fBfeature@\fR\fIfeature_name\fR property | |
27 | to \fBenabled\fR. | |
28 | .sp | |
29 | .LP | |
30 | The pool format does not affect file system version compatibility or the ability | |
31 | to send file systems between pools. | |
32 | .sp | |
33 | .LP | |
34 | Since most features can be enabled independently of each other the on\-disk | |
35 | format of the pool is specified by the set of all features marked as | |
36 | \fBactive\fR on the pool. If the pool was created by another software version | |
37 | this set may include unsupported features. | |
38 | .SS "Identifying features" | |
39 | .sp | |
40 | .LP | |
41 | Every feature has a guid of the form \fIcom.example:feature_name\fR. The reverse | |
42 | DNS name ensures that the feature's guid is unique across all ZFS | |
43 | implementations. When unsupported features are encountered on a pool they will | |
44 | be identified by their guids. Refer to the documentation for the ZFS | |
45 | implementation that created the pool for information about those features. | |
46 | .sp | |
47 | .LP | |
48 | Each supported feature also has a short name. By convention a feature's short | |
49 | name is the portion of its guid which follows the ':' (e.g. | |
50 | \fIcom.example:feature_name\fR would have the short name \fIfeature_name\fR), | |
51 | however a feature's short name may differ across ZFS implementations if | |
52 | following the convention would result in name conflicts. | |
53 | .SS "Feature states" | |
54 | .sp | |
55 | .LP | |
56 | Features can be in one of three states: | |
57 | .sp | |
58 | .ne 2 | |
59 | .na | |
60 | \fB\fBactive\fR\fR | |
61 | .ad | |
62 | .RS 12n | |
63 | This feature's on\-disk format changes are in effect on the pool. Support for | |
64 | this feature is required to import the pool in read\-write mode. If this | |
65 | feature is not read-only compatible, support is also required to import the pool | |
66 | in read\-only mode (see "Read\-only compatibility"). | |
67 | .RE | |
68 | ||
69 | .sp | |
70 | .ne 2 | |
71 | .na | |
72 | \fB\fBenabled\fR\fR | |
73 | .ad | |
74 | .RS 12n | |
75 | An administrator has marked this feature as enabled on the pool, but the | |
76 | feature's on\-disk format changes have not been made yet. The pool can still be | |
77 | imported by software that does not support this feature, but changes may be made | |
78 | to the on\-disk format at any time which will move the feature to the | |
79 | \fBactive\fR state. Some features may support returning to the \fBenabled\fR | |
80 | state after becoming \fBactive\fR. See feature\-specific documentation for | |
81 | details. | |
82 | .RE | |
83 | ||
84 | .sp | |
85 | .ne 2 | |
86 | .na | |
87 | \fBdisabled\fR | |
88 | .ad | |
89 | .RS 12n | |
90 | This feature's on\-disk format changes have not been made and will not be made | |
91 | unless an administrator moves the feature to the \fBenabled\fR state. Features | |
92 | cannot be disabled once they have been enabled. | |
93 | .RE | |
94 | ||
95 | .sp | |
96 | .LP | |
97 | The state of supported features is exposed through pool properties of the form | |
98 | \fIfeature@short_name\fR. | |
99 | .SS "Read\-only compatibility" | |
100 | .sp | |
101 | .LP | |
102 | Some features may make on\-disk format changes that do not interfere with other | |
103 | software's ability to read from the pool. These features are referred to as | |
104 | "read\-only compatible". If all unsupported features on a pool are read\-only | |
105 | compatible, the pool can be imported in read\-only mode by setting the | |
106 | \fBreadonly\fR property during import (see \fBzpool\fR(8) for details on | |
107 | importing pools). | |
108 | .SS "Unsupported features" | |
109 | .sp | |
110 | .LP | |
111 | For each unsupported feature enabled on an imported pool a pool property | |
112 | named \fIunsupported@feature_guid\fR will indicate why the import was allowed | |
113 | despite the unsupported feature. Possible values for this property are: | |
114 | ||
115 | .sp | |
116 | .ne 2 | |
117 | .na | |
118 | \fB\fBinactive\fR\fR | |
119 | .ad | |
120 | .RS 12n | |
121 | The feature is in the \fBenabled\fR state and therefore the pool's on\-disk | |
122 | format is still compatible with software that does not support this feature. | |
123 | .RE | |
124 | ||
125 | .sp | |
126 | .ne 2 | |
127 | .na | |
128 | \fB\fBreadonly\fR\fR | |
129 | .ad | |
130 | .RS 12n | |
131 | The feature is read\-only compatible and the pool has been imported in | |
132 | read\-only mode. | |
133 | .RE | |
134 | ||
135 | .SS "Feature dependencies" | |
136 | .sp | |
137 | .LP | |
138 | Some features depend on other features being enabled in order to function | |
139 | properly. Enabling a feature will automatically enable any features it | |
140 | depends on. | |
141 | .SH FEATURES | |
142 | .sp | |
143 | .LP | |
144 | The following features are supported on this system: | |
145 | .sp | |
146 | .ne 2 | |
147 | .na | |
148 | \fB\fBasync_destroy\fR\fR | |
149 | .ad | |
150 | .RS 4n | |
151 | .TS | |
152 | l l . | |
153 | GUID com.delphix:async_destroy | |
154 | READ\-ONLY COMPATIBLE yes | |
155 | DEPENDENCIES none | |
156 | .TE | |
157 | ||
158 | Destroying a file system requires traversing all of its data in order to | |
159 | return its used space to the pool. Without \fBasync_destroy\fR the file system | |
160 | is not fully removed until all space has been reclaimed. If the destroy | |
161 | operation is interrupted by a reboot or power outage the next attempt to open | |
162 | the pool will need to complete the destroy operation synchronously. | |
163 | ||
164 | When \fBasync_destroy\fR is enabled the file system's data will be reclaimed | |
165 | by a background process, allowing the destroy operation to complete without | |
166 | traversing the entire file system. The background process is able to resume | |
167 | interrupted destroys after the pool has been opened, eliminating the need | |
168 | to finish interrupted destroys as part of the open operation. The amount | |
169 | of space remaining to be reclaimed by the background process is available | |
170 | through the \fBfreeing\fR property. | |
171 | ||
172 | This feature is only \fBactive\fR while \fBfreeing\fR is non\-zero. | |
173 | .RE | |
174 | ||
175 | .sp | |
176 | .ne 2 | |
177 | .na | |
178 | \fB\fBempty_bpobj\fR\fR | |
179 | .ad | |
180 | .RS 4n | |
181 | .TS | |
182 | l l . | |
183 | GUID com.delphix:empty_bpobj | |
184 | READ\-ONLY COMPATIBLE yes | |
185 | DEPENDENCIES none | |
186 | .TE | |
187 | ||
188 | This feature increases the performance of creating and using a large | |
189 | number of snapshots of a single filesystem or volume, and also reduces | |
190 | the disk space required. | |
191 | ||
192 | When there are many snapshots, each snapshot uses many Block Pointer | |
193 | Objects (bpobj's) to track blocks associated with that snapshot. | |
194 | However, in common use cases, most of these bpobj's are empty. This | |
195 | feature allows us to create each bpobj on-demand, thus eliminating the | |
196 | empty bpobjs. | |
197 | ||
198 | This feature is \fBactive\fR while there are any filesystems, volumes, | |
199 | or snapshots which were created after enabling this feature. | |
200 | .RE | |
201 | ||
202 | .sp | |
203 | .ne 2 | |
204 | .na | |
205 | \fB\fBfilesystem_limits\fR\fR | |
206 | .ad | |
207 | .RS 4n | |
208 | .TS | |
209 | l l . | |
210 | GUID com.joyent:filesystem_limits | |
211 | READ\-ONLY COMPATIBLE yes | |
212 | DEPENDENCIES extensible_dataset | |
213 | .TE | |
214 | ||
215 | This feature enables filesystem and snapshot limits. These limits can be used | |
216 | to control how many filesystems and/or snapshots can be created at the point in | |
217 | the tree on which the limits are set. | |
218 | ||
219 | This feature is \fBactive\fR once either of the limit properties has been | |
220 | set on a dataset. Once activated the feature is never deactivated. | |
221 | .RE | |
222 | ||
223 | .sp | |
224 | .ne 2 | |
225 | .na | |
226 | \fB\fBlz4_compress\fR\fR | |
227 | .ad | |
228 | .RS 4n | |
229 | .TS | |
230 | l l . | |
231 | GUID org.illumos:lz4_compress | |
232 | READ\-ONLY COMPATIBLE no | |
233 | DEPENDENCIES none | |
234 | .TE | |
235 | ||
236 | \fBlz4\fR is a high-performance real-time compression algorithm that | |
237 | features significantly faster compression and decompression as well as a | |
238 | higher compression ratio than the older \fBlzjb\fR compression. | |
239 | Typically, \fBlz4\fR compression is approximately 50% faster on | |
240 | compressible data and 200% faster on incompressible data than | |
241 | \fBlzjb\fR. It is also approximately 80% faster on decompression, while | |
242 | giving approximately 10% better compression ratio. | |
243 | ||
244 | When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the | |
245 | administrator can turn on \fBlz4\fR compression on any dataset on the | |
246 | pool using the \fBzfs\fR(8) command. Please note that doing so will | |
247 | immediately activate the \fBlz4_compress\fR feature on the underlying | |
248 | pool using the \fBzfs\fR(1M) command. Also, all newly written metadata | |
249 | will be compressed with \fBlz4\fR algorithm. Since this feature is not | |
250 | read-only compatible, this operation will render the pool unimportable | |
251 | on systems without support for the \fBlz4_compress\fR feature. | |
252 | ||
253 | Booting off of \fBlz4\fR-compressed root pools is supported. | |
254 | ||
255 | This feature becomes \fBactive\fR as soon as it is enabled and will | |
256 | never return to being \fBenabled\fB. | |
257 | .RE | |
258 | ||
259 | .sp | |
260 | .ne 2 | |
261 | .na | |
262 | \fB\fBspacemap_histogram\fR\fR | |
263 | .ad | |
264 | .RS 4n | |
265 | .TS | |
266 | l l . | |
267 | GUID com.delphix:spacemap_histogram | |
268 | READ\-ONLY COMPATIBLE yes | |
269 | DEPENDENCIES none | |
270 | .TE | |
271 | ||
272 | This features allows ZFS to maintain more information about how free space | |
273 | is organized within the pool. If this feature is \fBenabled\fR, ZFS will | |
274 | set this feature to \fBactive\fR when a new space map object is created or | |
275 | an existing space map is upgraded to the new format. Once the feature is | |
276 | \fBactive\fR, it will remain in that state until the pool is destroyed. | |
277 | ||
278 | .RE | |
279 | ||
280 | .sp | |
281 | .ne 2 | |
282 | .na | |
283 | \fB\fBmulti_vdev_crash_dump\fR\fR | |
284 | .ad | |
285 | .RS 4n | |
286 | .TS | |
287 | l l . | |
288 | GUID com.joyent:multi_vdev_crash_dump | |
289 | READ\-ONLY COMPATIBLE no | |
290 | DEPENDENCIES none | |
291 | .TE | |
292 | ||
293 | This feature allows a dump device to be configured with a pool comprised | |
294 | of multiple vdevs. Those vdevs may be arranged in any mirrored or raidz | |
295 | configuration. | |
296 | ||
297 | When the \fBmulti_vdev_crash_dump\fR feature is set to \fBenabled\fR, | |
298 | the administrator can use the \fBdumpadm\fR(1M) command to configure a | |
299 | dump device on a pool comprised of multiple vdevs. | |
300 | ||
301 | Under Linux this feature is registered for compatibility but not used. | |
302 | New pools created under Linux will have the feature \fBenabled\fR but | |
303 | will never transition to \fB\fBactive\fR. This functionality is not | |
304 | required in order to support crash dumps under Linux. Existing pools | |
305 | where this feature is \fB\fBactive\fR can be imported. | |
306 | .RE | |
307 | ||
308 | .sp | |
309 | .ne 2 | |
310 | .na | |
311 | \fB\fBextensible_dataset\fR\fR | |
312 | .ad | |
313 | .RS 4n | |
314 | .TS | |
315 | l l . | |
316 | GUID com.delphix:extensible_dataset | |
317 | READ\-ONLY COMPATIBLE no | |
318 | DEPENDENCIES none | |
319 | .TE | |
320 | ||
321 | This feature allows more flexible use of internal ZFS data structures, | |
322 | and exists for other features to depend on. | |
323 | ||
324 | This feature will be \fBactive\fR when the first dependent feature uses it, | |
325 | and will be returned to the \fBenabled\fR state when all datasets that use | |
326 | this feature are destroyed. | |
327 | ||
328 | .RE | |
329 | ||
330 | .sp | |
331 | .ne 2 | |
332 | .na | |
333 | \fB\fBbookmarks\fR\fR | |
334 | .ad | |
335 | .RS 4n | |
336 | .TS | |
337 | l l . | |
338 | GUID com.delphix:bookmarks | |
339 | READ\-ONLY COMPATIBLE yes | |
340 | DEPENDENCIES extensible_dataset | |
341 | .TE | |
342 | ||
343 | This feature enables use of the \fBzfs bookmark\fR subcommand. | |
344 | ||
345 | This feature is \fBactive\fR while any bookmarks exist in the pool. | |
346 | All bookmarks in the pool can be listed by running | |
347 | \fBzfs list -t bookmark -r \fIpoolname\fR\fR. | |
348 | ||
349 | .RE | |
350 | ||
351 | .sp | |
352 | .ne 2 | |
353 | .na | |
354 | \fB\fBenabled_txg\fR\fR | |
355 | .ad | |
356 | .RS 4n | |
357 | .TS | |
358 | l l . | |
359 | GUID com.delphix:enabled_txg | |
360 | READ\-ONLY COMPATIBLE yes | |
361 | DEPENDENCIES none | |
362 | .TE | |
363 | ||
364 | Once this feature is enabled ZFS records the transaction group number | |
365 | in which new features are enabled. This has no user-visible impact, | |
366 | but other features may depend on this feature. | |
367 | ||
368 | This feature becomes \fBactive\fR as soon as it is enabled and will | |
369 | never return to being \fBenabled\fB. | |
370 | ||
371 | .RE | |
372 | ||
373 | .sp | |
374 | .ne 2 | |
375 | .na | |
376 | \fB\fBhole_birth\fR\fR | |
377 | .ad | |
378 | .RS 4n | |
379 | .TS | |
380 | l l . | |
381 | GUID com.delphix:hole_birth | |
382 | READ\-ONLY COMPATIBLE no | |
383 | DEPENDENCIES enabled_txg | |
384 | .TE | |
385 | ||
386 | This feature improves performance of incremental sends ("zfs send -i") | |
387 | and receives for objects with many holes. The most common case of | |
388 | hole-filled objects is zvols. | |
389 | ||
390 | An incremental send stream from snapshot \fBA\fR to snapshot \fBB\fR | |
391 | contains information about every block that changed between \fBA\fR and | |
392 | \fBB\fR. Blocks which did not change between those snapshots can be | |
393 | identified and omitted from the stream using a piece of metadata called | |
394 | the 'block birth time', but birth times are not recorded for holes (blocks | |
395 | filled only with zeroes). Since holes created after \fBA\fR cannot be | |
396 | distinguished from holes created before \fBA\fR, information about every | |
397 | hole in the entire filesystem or zvol is included in the send stream. | |
398 | ||
399 | For workloads where holes are rare this is not a problem. However, when | |
400 | incrementally replicating filesystems or zvols with many holes (for | |
401 | example a zvol formatted with another filesystem) a lot of time will | |
402 | be spent sending and receiving unnecessary information about holes that | |
403 | already exist on the receiving side. | |
404 | ||
405 | Once the \fBhole_birth\fR feature has been enabled the block birth times | |
406 | of all new holes will be recorded. Incremental sends between snapshots | |
407 | created after this feature is enabled will use this new metadata to avoid | |
408 | sending information about holes that already exist on the receiving side. | |
409 | ||
410 | This feature becomes \fBactive\fR as soon as it is enabled and will | |
411 | never return to being \fBenabled\fB. | |
412 | ||
413 | .RE | |
414 | ||
415 | .sp | |
416 | .ne 2 | |
417 | .na | |
418 | \fB\fBembedded_data\fR\fR | |
419 | .ad | |
420 | .RS 4n | |
421 | .TS | |
422 | l l . | |
423 | GUID com.delphix:embedded_data | |
424 | READ\-ONLY COMPATIBLE no | |
425 | DEPENDENCIES none | |
426 | .TE | |
427 | ||
428 | This feature improves the performance and compression ratio of | |
429 | highly-compressible blocks. Blocks whose contents can compress to 112 bytes | |
430 | or smaller can take advantage of this feature. | |
431 | ||
432 | When this feature is enabled, the contents of highly-compressible blocks are | |
433 | stored in the block "pointer" itself (a misnomer in this case, as it contains | |
434 | the compressed data, rather than a pointer to its location on disk). Thus | |
435 | the space of the block (one sector, typically 512 bytes or 4KB) is saved, | |
436 | and no additional i/o is needed to read and write the data block. | |
437 | ||
438 | This feature becomes \fBactive\fR as soon as it is enabled and will | |
439 | never return to being \fBenabled\fR. | |
440 | ||
441 | .RE | |
442 | .sp | |
443 | .ne 2 | |
444 | .na | |
445 | \fB\fBdevice_removal\fR\fR | |
446 | .ad | |
447 | .RS 4n | |
448 | .TS | |
449 | l l . | |
450 | GUID com.delphix:device_removal | |
451 | READ\-ONLY COMPATIBLE no | |
452 | DEPENDENCIES none | |
453 | .TE | |
454 | ||
455 | This feature enables the "zpool remove" subcommand to remove top-level | |
456 | vdevs, evacuating them to reduce the total size of the pool. | |
457 | ||
458 | This feature becomes \fBactive\fR when the "zpool remove" command is used | |
459 | on a top-level vdev, and will never return to being \fBenabled\fR. | |
460 | ||
461 | .RE | |
462 | .sp | |
463 | .ne 2 | |
464 | .na | |
465 | \fB\fBobsolete_counts\fR\fR | |
466 | .ad | |
467 | .RS 4n | |
468 | .TS | |
469 | l l . | |
470 | GUID com.delphix:obsolete_counts | |
471 | READ\-ONLY COMPATIBLE yes | |
472 | DEPENDENCIES device_removal | |
473 | .TE | |
474 | ||
475 | This feature is an enhancement of device_removal, which will over time | |
476 | reduce the memory used to track removed devices. When indirect blocks | |
477 | are freed or remapped, we note that their part of the indirect mapping | |
478 | is "obsolete", i.e. no longer needed. See also the \fBzfs remap\fR | |
479 | subcommand in \fBzfs\fR(1M). | |
480 | ||
481 | This feature becomes \fBactive\fR when the "zpool remove" command is | |
482 | used on a top-level vdev, and will never return to being \fBenabled\fR. | |
483 | ||
484 | .RE | |
485 | .sp | |
486 | .ne 2 | |
487 | .na | |
488 | \fB\fBzpool_checkpoint\fR\fR | |
489 | .ad | |
490 | .RS 4n | |
491 | .TS | |
492 | l l . | |
493 | GUID com.delphix:zpool_checkpoint | |
494 | READ\-ONLY COMPATIBLE yes | |
495 | DEPENDENCIES none | |
496 | .TE | |
497 | ||
498 | This feature enables the "zpool checkpoint" subcommand that can | |
499 | checkpoint the state of the pool at the time it was issued and later | |
500 | rewind back to it or discard it. | |
501 | ||
502 | This feature becomes \fBactive\fR when the "zpool checkpoint" command | |
503 | is used to checkpoint the pool. | |
504 | The feature will only return back to being \fBenabled\fR when the pool | |
505 | is rewound or the checkpoint has been discarded. | |
506 | ||
507 | .RE | |
508 | .sp | |
509 | .ne 2 | |
510 | .na | |
511 | \fB\fBspacemap_v2\fR\fR | |
512 | .ad | |
513 | .RS 4n | |
514 | .TS | |
515 | l l . | |
516 | GUID com.delphix:spacemap_v2 | |
517 | READ\-ONLY COMPATIBLE yes | |
518 | DEPENDENCIES none | |
519 | .TE | |
520 | ||
521 | This feature enables the use of the new space map encoding which | |
522 | consists of two words (instead of one) whenever it is advantageous. | |
523 | The new encoding allows space maps to represent large regions of | |
524 | space more efficiently on-disk while also increasing their maximum | |
525 | addressable offset. | |
526 | ||
527 | This feature becomes \fBactive\fR once it is \fBenabled\fR, and never | |
528 | returns back to being \fBenabled\fR. | |
529 | ||
530 | .RE | |
531 | .sp | |
532 | .ne 2 | |
533 | .na | |
534 | \fB\fBlarge_blocks\fR\fR | |
535 | .ad | |
536 | .RS 4n | |
537 | .TS | |
538 | l l . | |
539 | GUID org.open-zfs:large_block | |
540 | READ\-ONLY COMPATIBLE no | |
541 | DEPENDENCIES extensible_dataset | |
542 | .TE | |
543 | ||
544 | The \fBlarge_block\fR feature allows the record size on a dataset to be | |
545 | set larger than 128KB. | |
546 | ||
547 | This feature becomes \fBactive\fR once a dataset contains a file with | |
548 | a block size larger than 128KB, and will return to being \fBenabled\fR once all | |
549 | filesystems that have ever had their recordsize larger than 128KB are destroyed. | |
550 | .RE | |
551 | ||
552 | .sp | |
553 | .ne 2 | |
554 | .na | |
555 | \fB\fBlarge_dnode\fR\fR | |
556 | .ad | |
557 | .RS 4n | |
558 | .TS | |
559 | l l . | |
560 | GUID org.zfsonlinux:large_dnode | |
561 | READ\-ONLY COMPATIBLE no | |
562 | DEPENDENCIES extensible_dataset | |
563 | .TE | |
564 | ||
565 | The \fBlarge_dnode\fR feature allows the size of dnodes in a dataset to be | |
566 | set larger than 512B. | |
567 | ||
568 | This feature becomes \fBactive\fR once a dataset contains an object with | |
569 | a dnode larger than 512B, which occurs as a result of setting the | |
570 | \fBdnodesize\fR dataset property to a value other than \fBlegacy\fR. The | |
571 | feature will return to being \fBenabled\fR once all filesystems that | |
572 | have ever contained a dnode larger than 512B are destroyed. Large dnodes | |
573 | allow more data to be stored in the bonus buffer, thus potentially | |
574 | improving performance by avoiding the use of spill blocks. | |
575 | .RE | |
576 | ||
577 | \fB\fBsha512\fR\fR | |
578 | .ad | |
579 | .RS 4n | |
580 | .TS | |
581 | l l . | |
582 | GUID org.illumos:sha512 | |
583 | READ\-ONLY COMPATIBLE no | |
584 | DEPENDENCIES extensible_dataset | |
585 | .TE | |
586 | ||
587 | This feature enables the use of the SHA-512/256 truncated hash algorithm | |
588 | (FIPS 180-4) for checksum and dedup. The native 64-bit arithmetic of | |
589 | SHA-512 provides an approximate 50% performance boost over SHA-256 on | |
590 | 64-bit hardware and is thus a good minimum-change replacement candidate | |
591 | for systems where hash performance is important, but these systems | |
592 | cannot for whatever reason utilize the faster \fBskein\fR and | |
593 | \fBedonr\fR algorithms. | |
594 | ||
595 | When the \fBsha512\fR feature is set to \fBenabled\fR, the administrator | |
596 | can turn on the \fBsha512\fR checksum on any dataset using the | |
597 | \fBzfs set checksum=sha512\fR(1M) command. This feature becomes | |
598 | \fBactive\fR once a \fBchecksum\fR property has been set to \fBsha512\fR, | |
599 | and will return to being \fBenabled\fR once all filesystems that have | |
600 | ever had their checksum set to \fBsha512\fR are destroyed. | |
601 | ||
602 | Booting off of pools utilizing SHA-512/256 is supported. | |
603 | ||
604 | .RE | |
605 | ||
606 | .sp | |
607 | .ne 2 | |
608 | .na | |
609 | \fB\fBskein\fR\fR | |
610 | .ad | |
611 | .RS 4n | |
612 | .TS | |
613 | l l . | |
614 | GUID org.illumos:skein | |
615 | READ\-ONLY COMPATIBLE no | |
616 | DEPENDENCIES extensible_dataset | |
617 | .TE | |
618 | ||
619 | This feature enables the use of the Skein hash algorithm for checksum | |
620 | and dedup. Skein is a high-performance secure hash algorithm that was a | |
621 | finalist in the NIST SHA-3 competition. It provides a very high security | |
622 | margin and high performance on 64-bit hardware (80% faster than | |
623 | SHA-256). This implementation also utilizes the new salted checksumming | |
624 | functionality in ZFS, which means that the checksum is pre-seeded with a | |
625 | secret 256-bit random key (stored on the pool) before being fed the data | |
626 | block to be checksummed. Thus the produced checksums are unique to a | |
627 | given pool, preventing hash collision attacks on systems with dedup. | |
628 | ||
629 | When the \fBskein\fR feature is set to \fBenabled\fR, the administrator | |
630 | can turn on the \fBskein\fR checksum on any dataset using the | |
631 | \fBzfs set checksum=skein\fR(1M) command. This feature becomes | |
632 | \fBactive\fR once a \fBchecksum\fR property has been set to \fBskein\fR, | |
633 | and will return to being \fBenabled\fR once all filesystems that have | |
634 | ever had their checksum set to \fBskein\fR are destroyed. | |
635 | ||
636 | Booting off of pools using \fBskein\fR is supported. | |
637 | ||
638 | .RE | |
639 | ||
640 | .sp | |
641 | .ne 2 | |
642 | .na | |
643 | \fB\fBedonr\fR\fR | |
644 | .ad | |
645 | .RS 4n | |
646 | .TS | |
647 | l l . | |
648 | GUID org.illumos:edonr | |
649 | READ\-ONLY COMPATIBLE no | |
650 | DEPENDENCIES extensible_dataset | |
651 | .TE | |
652 | ||
653 | This feature enables the use of the Edon-R hash algorithm for checksum, | |
654 | including for nopwrite (if compression is also enabled, an overwrite of | |
655 | a block whose checksum matches the data being written will be ignored). | |
656 | In an abundance of caution, Edon-R can not be used with dedup | |
657 | (without verification). | |
658 | ||
659 | Edon-R is a very high-performance hash algorithm that was part | |
660 | of the NIST SHA-3 competition. It provides extremely high hash | |
661 | performance (over 350% faster than SHA-256), but was not selected | |
662 | because of its unsuitability as a general purpose secure hash algorithm. | |
663 | This implementation utilizes the new salted checksumming functionality | |
664 | in ZFS, which means that the checksum is pre-seeded with a secret | |
665 | 256-bit random key (stored on the pool) before being fed the data block | |
666 | to be checksummed. Thus the produced checksums are unique to a given | |
667 | pool. | |
668 | ||
669 | When the \fBedonr\fR feature is set to \fBenabled\fR, the administrator | |
670 | can turn on the \fBedonr\fR checksum on any dataset using the | |
671 | \fBzfs set checksum=edonr\fR(1M) command. This feature becomes | |
672 | \fBactive\fR once a \fBchecksum\fR property has been set to \fBedonr\fR, | |
673 | and will return to being \fBenabled\fR once all filesystems that have | |
674 | ever had their checksum set to \fBedonr\fR are destroyed. | |
675 | ||
676 | Booting off of pools using \fBedonr\fR is supported. | |
677 | ||
678 | .RE | |
679 | ||
680 | .sp | |
681 | .ne 2 | |
682 | .na | |
683 | \fB\fBuserobj_accounting\fR\fR | |
684 | .ad | |
685 | .RS 4n | |
686 | .TS | |
687 | l l . | |
688 | GUID org.zfsonlinux:userobj_accounting | |
689 | READ\-ONLY COMPATIBLE yes | |
690 | DEPENDENCIES extensible_dataset | |
691 | .TE | |
692 | ||
693 | This feature allows administrators to account the object usage information | |
694 | by user and group. | |
695 | ||
696 | This feature becomes \fBactive\fR as soon as it is enabled and will never | |
697 | return to being \fBenabled\fR. Each filesystem will be upgraded automatically | |
698 | when remounted, or when new files are created under that filesystem. | |
699 | The upgrade can also be started manually on filesystems by running | |
700 | `zfs set version=current <pool/fs>`. The upgrade process runs in the background | |
701 | and may take a while to complete for filesystems containing a large number of | |
702 | files. | |
703 | ||
704 | .RE | |
705 | ||
706 | .sp | |
707 | .ne 2 | |
708 | .na | |
709 | \fB\fBencryption\fR\fR | |
710 | .ad | |
711 | .RS 4n | |
712 | .TS | |
713 | l l . | |
714 | GUID com.datto:encryption | |
715 | READ\-ONLY COMPATIBLE no | |
716 | DEPENDENCIES extensible_dataset | |
717 | .TE | |
718 | ||
719 | This feature enables the creation and management of natively encrypted datasets. | |
720 | ||
721 | This feature becomes \fBactive\fR when an encrypted dataset is created and will | |
722 | be returned to the \fBenabled\fR state when all datasets that use this feature | |
723 | are destroyed. | |
724 | ||
725 | .RE | |
726 | ||
727 | .sp | |
728 | .ne 2 | |
729 | .na | |
730 | \fB\fBproject_quota\fR\fR | |
731 | .ad | |
732 | .RS 4n | |
733 | .TS | |
734 | l l . | |
735 | GUID org.zfsonlinux:project_quota | |
736 | READ\-ONLY COMPATIBLE yes | |
737 | DEPENDENCIES extensible_dataset | |
738 | .TE | |
739 | ||
740 | This feature allows administrators to account the spaces and objects usage | |
741 | information against the project identifier (ID). | |
742 | ||
743 | The project ID is new object-based attribute. When upgrading an existing | |
744 | filesystem, object without project ID attribute will be assigned a zero | |
745 | project ID. After this feature is enabled, newly created object will inherit | |
746 | its parent directory's project ID if the parent inherit flag is set (via | |
747 | \fBchattr +/-P\fR or \fBzfs project [-s|-C]\fR). Otherwise, the new object's | |
748 | project ID will be set as zero. An object's project ID can be changed at | |
749 | anytime by the owner (or privileged user) via \fBchattr -p $prjid\fR or | |
750 | \fBzfs project -p $prjid\fR. | |
751 | ||
752 | This feature will become \fBactive\fR as soon as it is enabled and will never | |
753 | return to being \fBdisabled\fR. Each filesystem will be upgraded automatically | |
754 | when remounted or when new file is created under that filesystem. The upgrade | |
755 | can also be triggered on filesystems via `zfs set version=current <pool/fs>`. | |
756 | The upgrade process runs in the background and may take a while to complete | |
757 | for the filesystems containing a large number of files. | |
758 | ||
759 | .RE | |
760 | ||
761 | .sp | |
762 | .ne 2 | |
763 | .na | |
764 | \fB\fBallocation_classes\fR\fR | |
765 | .ad | |
766 | .RS 4n | |
767 | .TS | |
768 | l l . | |
769 | GUID com.intel:allocation_classes | |
770 | READ\-ONLY COMPATIBLE yes | |
771 | DEPENDENCIES none | |
772 | .TE | |
773 | ||
774 | This feature enables support for separate allocation classes. | |
775 | ||
776 | This feature becomes \fBactive\fR when a dedicated allocation class vdev | |
777 | (dedup or special) is created with zpool create or zpool add. With device | |
778 | removal, it can be returned to the \fBenabled\fR state if all the top-level | |
779 | vdevs from an allocation class are removed. | |
780 | ||
781 | .RE | |
782 | ||
783 | .SH "SEE ALSO" | |
784 | \fBzpool\fR(8) |