1.\" 2.\" Copyright (c) 2012, 2018 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 https://opensource.org/licenses/CDDL-1.0. 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.\" Copyright (c) 2019, Klara Inc. 18.\" Copyright (c) 2019, Allan Jude 19.\" Copyright (c) 2021, Colm Buckley <colm@tuatha.org> 20.\" 21.Dd June 23, 2022 22.Dt ZPOOL-FEATURES 7 23.Os 24. 25.Sh NAME 26.Nm zpool-features 27.Nd description of ZFS pool features 28. 29.Sh DESCRIPTION 30ZFS pool on-disk format versions are specified via 31.Dq features 32which replace the old on-disk format numbers 33.Pq the last supported on-disk format number is 28 . 34To enable a feature on a pool use the 35.Nm zpool Cm upgrade , 36or set the 37.Sy feature Ns @ Ns Ar feature-name 38property to 39.Sy enabled . 40Please also see the 41.Sx Compatibility feature sets 42section for information on how sets of features may be enabled together. 43.Pp 44The pool format does not affect file system version compatibility or the ability 45to send file systems between pools. 46.Pp 47Since most features can be enabled independently of each other, the on-disk 48format of the pool is specified by the set of all features marked as 49.Sy active 50on the pool. 51If the pool was created by another software version 52this set may include unsupported features. 53. 54.Ss Identifying features 55Every feature has a GUID of the form 56.Ar com.example : Ns Ar feature-name . 57The reversed DNS name ensures that the feature's GUID is unique across all ZFS 58implementations. 59When unsupported features are encountered on a pool they will 60be identified by their GUIDs. 61Refer to the documentation for the ZFS 62implementation that created the pool for information about those features. 63.Pp 64Each supported feature also has a short name. 65By convention a feature's short name is the portion of its GUID which follows 66the 67.Sq \&: 68.Po 69i.e. 70.Ar com.example : Ns Ar feature-name 71would have the short name 72.Ar feature-name 73.Pc , 74however a feature's short name may differ across ZFS implementations if 75following the convention would result in name conflicts. 76. 77.Ss Feature states 78Features can be in one of three states: 79.Bl -tag -width "disabled" 80.It Sy active 81This feature's on-disk format changes are in effect on the pool. 82Support for this feature is required to import the pool in read-write mode. 83If this feature is not read-only compatible, 84support is also required to import the pool in read-only mode 85.Pq see Sx Read-only compatibility . 86.It Sy enabled 87An administrator has marked this feature as enabled on the pool, but the 88feature's on-disk format changes have not been made yet. 89The pool can still be imported by software that does not support this feature, 90but changes may be made to the on-disk format at any time 91which will move the feature to the 92.Sy active 93state. 94Some features may support returning to the 95.Sy enabled 96state after becoming 97.Sy active . 98See feature-specific documentation for details. 99.It Sy disabled 100This feature's on-disk format changes have not been made and will not be made 101unless an administrator moves the feature to the 102.Sy enabled 103state. 104Features cannot be disabled once they have been enabled. 105.El 106.Pp 107The state of supported features is exposed through pool properties of the form 108.Sy feature Ns @ Ns Ar short-name . 109. 110.Ss Read-only compatibility 111Some features may make on-disk format changes that do not interfere with other 112software's ability to read from the pool. 113These features are referred to as 114.Dq read-only compatible . 115If all unsupported features on a pool are read-only compatible, 116the pool can be imported in read-only mode by setting the 117.Sy readonly 118property during import 119.Po see 120.Xr zpool-import 8 121for details on importing pools 122.Pc . 123. 124.Ss Unsupported features 125For each unsupported feature enabled on an imported pool, a pool property 126named 127.Sy unsupported Ns @ Ns Ar feature-name 128will indicate why the import was allowed despite the unsupported feature. 129Possible values for this property are: 130.Bl -tag -width "readonly" 131.It Sy inactive 132The feature is in the 133.Sy enabled 134state and therefore the pool's on-disk 135format is still compatible with software that does not support this feature. 136.It Sy readonly 137The feature is read-only compatible and the pool has been imported in 138read-only mode. 139.El 140. 141.Ss Feature dependencies 142Some features depend on other features being enabled in order to function. 143Enabling a feature will automatically enable any features it depends on. 144. 145.Ss Compatibility feature sets 146It is sometimes necessary for a pool to maintain compatibility with a 147specific on-disk format, by enabling and disabling particular features. 148The 149.Sy compatibility 150feature facilitates this by allowing feature sets to be read from text files. 151When set to 152.Sy off 153.Pq the default , 154compatibility feature sets are disabled 155.Pq i.e. all features are enabled ; 156when set to 157.Sy legacy , 158no features are enabled. 159When set to a comma-separated list of filenames 160.Po 161each filename may either be an absolute path, or relative to 162.Pa /etc/zfs/compatibility.d 163or 164.Pa /usr/share/zfs/compatibility.d 165.Pc , 166the lists of requested features are read from those files, 167separated by whitespace and/or commas. 168Only features present in all files are enabled. 169.Pp 170Simple sanity checks are applied to the files: 171they must be between 1 B and 16 KiB in size, and must end with a newline 172character. 173.Pp 174The requested features are applied when a pool is created using 175.Nm zpool Cm create Fl o Sy compatibility Ns = Ns Ar … 176and controls which features are enabled when using 177.Nm zpool Cm upgrade . 178.Nm zpool Cm status 179will not show a warning about disabled features which are not part 180of the requested feature set. 181.Pp 182The special value 183.Sy legacy 184prevents any features from being enabled, either via 185.Nm zpool Cm upgrade 186or 187.Nm zpool Cm set Sy feature Ns @ Ns Ar feature-name Ns = Ns Sy enabled . 188This setting also prevents pools from being upgraded to newer on-disk versions. 189This is a safety measure to prevent new features from being 190accidentally enabled, breaking compatibility. 191.Pp 192By convention, compatibility files in 193.Pa /usr/share/zfs/compatibility.d 194are provided by the distribution, and include feature sets 195supported by important versions of popular distributions, and feature 196sets commonly supported at the start of each year. 197Compatibility files in 198.Pa /etc/zfs/compatibility.d , 199if present, will take precedence over files with the same name in 200.Pa /usr/share/zfs/compatibility.d . 201.Pp 202If an unrecognized feature is found in these files, an error message will 203be shown. 204If the unrecognized feature is in a file in 205.Pa /etc/zfs/compatibility.d , 206this is treated as an error and processing will stop. 207If the unrecognized feature is under 208.Pa /usr/share/zfs/compatibility.d , 209this is treated as a warning and processing will continue. 210This difference is to allow distributions to include features 211which might not be recognized by the currently-installed binaries. 212.Pp 213Compatibility files may include comments: 214any text from 215.Sq # 216to the end of the line is ignored. 217.Pp 218.Sy Example : 219.Bd -literal -compact -offset 4n 220.No example# Nm cat Pa /usr/share/zfs/compatibility.d/grub2 221# Features which are supported by GRUB2 222async_destroy 223bookmarks 224embedded_data 225empty_bpobj 226enabled_txg 227extensible_dataset 228filesystem_limits 229hole_birth 230large_blocks 231lz4_compress 232spacemap_histogram 233 234.No example# Nm zpool Cm create Fl o Sy compatibility Ns = Ns Ar grub2 Ar bootpool Ar vdev 235.Ed 236.Pp 237See 238.Xr zpool-create 8 239and 240.Xr zpool-upgrade 8 241for more information on how these commands are affected by feature sets. 242. 243.de feature 244.It Sy \\$2 245.Bl -tag -compact -width "READ-ONLY COMPATIBLE" 246.It GUID 247.Sy \\$1:\\$2 248.if !"\\$4"" \{\ 249.It DEPENDENCIES 250\fB\\$4\fP\c 251.if !"\\$5"" , \fB\\$5\fP\c 252.if !"\\$6"" , \fB\\$6\fP\c 253.if !"\\$7"" , \fB\\$7\fP\c 254.if !"\\$8"" , \fB\\$8\fP\c 255.if !"\\$9"" , \fB\\$9\fP\c 256.\} 257.It READ-ONLY COMPATIBLE 258\\$3 259.El 260.Pp 261.. 262. 263.ds instant-never \ 264.No This feature becomes Sy active No as soon as it is enabled \ 265and will never return to being Sy enabled . 266. 267.ds remount-upgrade \ 268.No Each filesystem will be upgraded automatically when remounted, \ 269or when a new file is created under that filesystem. \ 270The upgrade can also be triggered on filesystems via \ 271Nm zfs Cm set Sy version Ns = Ns Sy current Ar fs . \ 272No The upgrade process runs in the background and may take a while to complete \ 273for filesystems containing large amounts of files . 274. 275.de checksum-spiel 276When the 277.Sy \\$1 278feature is set to 279.Sy enabled , 280the administrator can turn on the 281.Sy \\$1 282checksum on any dataset using 283.Nm zfs Cm set Sy checksum Ns = Ns Sy \\$1 Ar dset 284.Po see Xr zfs-set 8 Pc . 285This feature becomes 286.Sy active 287once a 288.Sy checksum 289property has been set to 290.Sy \\$1 , 291and will return to being 292.Sy enabled 293once all filesystems that have ever had their checksum set to 294.Sy \\$1 295are destroyed. 296.. 297. 298.Sh FEATURES 299The following features are supported on this system: 300.Bl -tag -width Ds 301.feature org.zfsonlinux allocation_classes yes 302This feature enables support for separate allocation classes. 303.Pp 304This feature becomes 305.Sy active 306when a dedicated allocation class vdev 307.Pq dedup or special 308is created with the 309.Nm zpool Cm create No or Nm zpool Cm add No commands . 310With device removal, it can be returned to the 311.Sy enabled 312state if all the dedicated allocation class vdevs are removed. 313. 314.feature com.delphix async_destroy yes 315Destroying a file system requires traversing all of its data in order to 316return its used space to the pool. 317Without 318.Sy async_destroy , 319the file system is not fully removed until all space has been reclaimed. 320If the destroy operation is interrupted by a reboot or power outage, 321the next attempt to open the pool will need to complete the destroy 322operation synchronously. 323.Pp 324When 325.Sy async_destroy 326is enabled, the file system's data will be reclaimed by a background process, 327allowing the destroy operation to complete 328without traversing the entire file system. 329The background process is able to resume 330interrupted destroys after the pool has been opened, eliminating the need 331to finish interrupted destroys as part of the open operation. 332The amount of space remaining to be reclaimed by the background process 333is available through the 334.Sy freeing 335property. 336.Pp 337This feature is only 338.Sy active 339while 340.Sy freeing 341is non-zero. 342. 343.feature org.openzfs blake3 no extensible_dataset 344This feature enables the use of the BLAKE3 hash algorithm for checksum and 345dedup. 346BLAKE3 is a secure hash algorithm focused on high performance. 347.Pp 348.checksum-spiel blake3 349. 350.feature com.delphix bookmarks yes extensible_dataset 351This feature enables use of the 352.Nm zfs Cm bookmark 353command. 354.Pp 355This feature is 356.Sy active 357while any bookmarks exist in the pool. 358All bookmarks in the pool can be listed by running 359.Nm zfs Cm list Fl t Sy bookmark Fl r Ar poolname . 360. 361.feature com.datto bookmark_v2 no bookmark extensible_dataset 362This feature enables the creation and management of larger bookmarks which are 363needed for other features in ZFS. 364.Pp 365This feature becomes 366.Sy active 367when a v2 bookmark is created and will be returned to the 368.Sy enabled 369state when all v2 bookmarks are destroyed. 370. 371.feature com.delphix bookmark_written no bookmark extensible_dataset bookmark_v2 372This feature enables additional bookmark accounting fields, enabling the 373.Sy written Ns # Ns Ar bookmark 374property 375.Pq space written since a bookmark 376and estimates of send stream sizes for incrementals from bookmarks. 377.Pp 378This feature becomes 379.Sy active 380when a bookmark is created and will be 381returned to the 382.Sy enabled 383state when all bookmarks with these fields are destroyed. 384. 385.feature org.openzfs device_rebuild yes 386This feature enables the ability for the 387.Nm zpool Cm attach 388and 389.Nm zpool Cm replace 390commands to perform sequential reconstruction 391.Pq instead of healing reconstruction 392when resilvering. 393.Pp 394Sequential reconstruction resilvers a device in LBA order without immediately 395verifying the checksums. 396Once complete, a scrub is started, which then verifies the checksums. 397This approach allows full redundancy to be restored to the pool 398in the minimum amount of time. 399This two-phase approach will take longer than a healing resilver 400when the time to verify the checksums is included. 401However, unless there is additional pool damage, 402no checksum errors should be reported by the scrub. 403This feature is incompatible with raidz configurations. 404. 405This feature becomes 406.Sy active 407while a sequential resilver is in progress, and returns to 408.Sy enabled 409when the resilver completes. 410. 411.feature com.delphix device_removal no 412This feature enables the 413.Nm zpool Cm remove 414command to remove top-level vdevs, 415evacuating them to reduce the total size of the pool. 416.Pp 417This feature becomes 418.Sy active 419when the 420.Nm zpool Cm remove 421command is used 422on a top-level vdev, and will never return to being 423.Sy enabled . 424. 425.feature org.openzfs draid no 426This feature enables use of the 427.Sy draid 428vdev type. 429dRAID is a variant of RAID-Z which provides integrated distributed 430hot spares that allow faster resilvering while retaining the benefits of RAID-Z. 431Data, parity, and spare space are organized in redundancy groups 432and distributed evenly over all of the devices. 433.Pp 434This feature becomes 435.Sy active 436when creating a pool which uses the 437.Sy draid 438vdev type, or when adding a new 439.Sy draid 440vdev to an existing pool. 441. 442.feature org.illumos edonr no extensible_dataset 443This feature enables the use of the Edon-R hash algorithm for checksum, 444including for nopwrite 445.Po if compression is also enabled, an overwrite of 446a block whose checksum matches the data being written will be ignored 447.Pc . 448In an abundance of caution, Edon-R requires verification when used with 449dedup: 450.Nm zfs Cm set Sy dedup Ns = Ns Sy edonr , Ns Sy verify 451.Po see Xr zfs-set 8 Pc . 452.Pp 453Edon-R is a very high-performance hash algorithm that was part 454of the NIST SHA-3 competition. 455It provides extremely high hash performance 456.Pq over 350% faster than SHA-256 , 457but was not selected because of its unsuitability 458as a general purpose secure hash algorithm. 459This implementation utilizes the new salted checksumming functionality 460in ZFS, which means that the checksum is pre-seeded with a secret 461256-bit random key 462.Pq stored on the pool 463before being fed the data block to be checksummed. 464Thus the produced checksums are unique to a given pool, 465preventing hash collision attacks on systems with dedup. 466.Pp 467.checksum-spiel edonr 468. 469.feature com.delphix embedded_data no 470This feature improves the performance and compression ratio of 471highly-compressible blocks. 472Blocks whose contents can compress to 112 bytes 473or smaller can take advantage of this feature. 474.Pp 475When this feature is enabled, the contents of highly-compressible blocks are 476stored in the block 477.Dq pointer 478itself 479.Po a misnomer in this case, as it contains 480the compressed data, rather than a pointer to its location on disk 481.Pc . 482Thus the space of the block 483.Pq one sector, typically 512 B or 4 KiB 484is saved, and no additional I/O is needed to read and write the data block. 485. 486\*[instant-never] 487. 488.feature com.delphix empty_bpobj yes 489This feature increases the performance of creating and using a large 490number of snapshots of a single filesystem or volume, and also reduces 491the disk space required. 492.Pp 493When there are many snapshots, each snapshot uses many Block Pointer 494Objects 495.Pq bpobjs 496to track blocks associated with that snapshot. 497However, in common use cases, most of these bpobjs are empty. 498This feature allows us to create each bpobj on-demand, 499thus eliminating the empty bpobjs. 500.Pp 501This feature is 502.Sy active 503while there are any filesystems, volumes, 504or snapshots which were created after enabling this feature. 505. 506.feature com.delphix enabled_txg yes 507Once this feature is enabled, ZFS records the transaction group number 508in which new features are enabled. 509This has no user-visible impact, but other features may depend on this feature. 510.Pp 511This feature becomes 512.Sy active 513as soon as it is enabled and will never return to being 514.Sy enabled . 515. 516.feature com.datto encryption no bookmark_v2 extensible_dataset 517This feature enables the creation and management of natively encrypted datasets. 518.Pp 519This feature becomes 520.Sy active 521when an encrypted dataset is created and will be returned to the 522.Sy enabled 523state when all datasets that use this feature are destroyed. 524. 525.feature com.delphix extensible_dataset no 526This feature allows more flexible use of internal ZFS data structures, 527and exists for other features to depend on. 528.Pp 529This feature will be 530.Sy active 531when the first dependent feature uses it, and will be returned to the 532.Sy enabled 533state when all datasets that use this feature are destroyed. 534. 535.feature com.joyent filesystem_limits yes extensible_dataset 536This feature enables filesystem and snapshot limits. 537These limits can be used to control how many filesystems and/or snapshots 538can be created at the point in the tree on which the limits are set. 539.Pp 540This feature is 541.Sy active 542once either of the limit properties has been set on a dataset 543and will never return to being 544.Sy enabled . 545. 546.feature com.delphix head_errlog no 547This feature enables the upgraded version of errlog, which required an on-disk 548error log format change. 549Now the error log of each head dataset is stored separately in the zap object 550and keyed by the head id. 551In case of encrypted filesystems with unloaded keys or unmounted encrypted 552filesystems we are unable to check their snapshots or clones for errors and 553these will not be reported. 554With this feature enabled, every dataset affected by an error block is listed 555in the output of 556.Nm zpool Cm status . 557.Pp 558\*[instant-never] 559. 560.feature com.delphix hole_birth no enabled_txg 561This feature has/had bugs, the result of which is that, if you do a 562.Nm zfs Cm send Fl i 563.Pq or Fl R , No since it uses Fl i 564from an affected dataset, the receiving party will not see any checksum 565or other errors, but the resulting destination snapshot 566will not match the source. 567Its use by 568.Nm zfs Cm send Fl i 569has been disabled by default 570.Po 571see 572.Sy send_holes_without_birth_time 573in 574.Xr zfs 4 575.Pc . 576.Pp 577This feature improves performance of incremental sends 578.Pq Nm zfs Cm send Fl i 579and receives for objects with many holes. 580The most common case of hole-filled objects is zvols. 581.Pp 582An incremental send stream from snapshot 583.Sy A No to snapshot Sy B 584contains information about every block that changed between 585.Sy A No and Sy B . 586Blocks which did not change between those snapshots can be 587identified and omitted from the stream using a piece of metadata called 588the 589.Dq block birth time , 590but birth times are not recorded for holes 591.Pq blocks filled only with zeroes . 592Since holes created after 593.Sy A No cannot be distinguished from holes created before Sy A , 594information about every hole in the entire filesystem or zvol 595is included in the send stream. 596.Pp 597For workloads where holes are rare this is not a problem. 598However, when incrementally replicating filesystems or zvols with many holes 599.Pq for example a zvol formatted with another filesystem 600a lot of time will be spent sending and receiving unnecessary information 601about holes that already exist on the receiving side. 602.Pp 603Once the 604.Sy hole_birth 605feature has been enabled the block birth times 606of all new holes will be recorded. 607Incremental sends between snapshots created after this feature is enabled 608will use this new metadata to avoid sending information about holes that 609already exist on the receiving side. 610.Pp 611\*[instant-never] 612. 613.feature org.open-zfs large_blocks no extensible_dataset 614This feature allows the record size on a dataset to be set larger than 128 KiB. 615.Pp 616This feature becomes 617.Sy active 618once a dataset contains a file with a block size larger than 128 KiB, 619and will return to being 620.Sy enabled 621once all filesystems that have ever had their recordsize larger than 128 KiB 622are destroyed. 623. 624.feature org.zfsonlinux large_dnode no extensible_dataset 625This feature allows the size of dnodes in a dataset to be set larger than 512 B. 626. 627This feature becomes 628.Sy active 629once a dataset contains an object with a dnode larger than 512 B, 630which occurs as a result of setting the 631.Sy dnodesize 632dataset property to a value other than 633.Sy legacy . 634The feature will return to being 635.Sy enabled 636once all filesystems that have ever contained a dnode larger than 512 B 637are destroyed. 638Large dnodes allow more data to be stored in the bonus buffer, 639thus potentially improving performance by avoiding the use of spill blocks. 640. 641.feature com.delphix livelist yes 642This feature allows clones to be deleted faster than the traditional method 643when a large number of random/sparse writes have been made to the clone. 644All blocks allocated and freed after a clone is created are tracked by the 645the clone's livelist which is referenced during the deletion of the clone. 646The feature is activated when a clone is created and remains 647.Sy active 648until all clones have been destroyed. 649. 650.feature com.delphix log_spacemap yes com.delphix:spacemap_v2 651This feature improves performance for heavily-fragmented pools, 652especially when workloads are heavy in random-writes. 653It does so by logging all the metaslab changes on a single spacemap every TXG 654instead of scattering multiple writes to all the metaslab spacemaps. 655.Pp 656\*[instant-never] 657. 658.feature org.illumos lz4_compress no 659.Sy lz4 660is a high-performance real-time compression algorithm that 661features significantly faster compression and decompression as well as a 662higher compression ratio than the older 663.Sy lzjb 664compression. 665Typically, 666.Sy lz4 667compression is approximately 50% faster on compressible data and 200% faster 668on incompressible data than 669.Sy lzjb . 670It is also approximately 80% faster on decompression, 671while giving approximately a 10% better compression ratio. 672.Pp 673When the 674.Sy lz4_compress 675feature is set to 676.Sy enabled , 677the administrator can turn on 678.Sy lz4 679compression on any dataset on the pool using the 680.Xr zfs-set 8 681command. 682All newly written metadata will be compressed with the 683.Sy lz4 684algorithm. 685.Pp 686\*[instant-never] 687. 688.feature com.joyent multi_vdev_crash_dump no 689This feature allows a dump device to be configured with a pool comprised 690of multiple vdevs. 691Those vdevs may be arranged in any mirrored or raidz configuration. 692.Pp 693When the 694.Sy multi_vdev_crash_dump 695feature is set to 696.Sy enabled , 697the administrator can use 698.Xr dumpadm 8 699to configure a dump device on a pool comprised of multiple vdevs. 700.Pp 701Under 702.Fx 703and Linux this feature is unused, but registered for compatibility. 704New pools created on these systems will have the feature 705.Sy enabled 706but will never transition to 707.Sy active , 708as this functionality is not required for crash dump support. 709Existing pools where this feature is 710.Sy active 711can be imported. 712. 713.feature com.delphix obsolete_counts yes device_removal 714This feature is an enhancement of 715.Sy device_removal , 716which will over time reduce the memory used to track removed devices. 717When indirect blocks are freed or remapped, 718we note that their part of the indirect mapping is 719.Dq obsolete 720– no longer needed. 721.Pp 722This feature becomes 723.Sy active 724when the 725.Nm zpool Cm remove 726command is used on a top-level vdev, and will never return to being 727.Sy enabled . 728. 729.feature org.zfsonlinux project_quota yes extensible_dataset 730This feature allows administrators to account the spaces and objects usage 731information against the project identifier 732.Pq ID . 733.Pp 734The project ID is an object-based attribute. 735When upgrading an existing filesystem, 736objects without a project ID will be assigned a zero project ID. 737When this feature is enabled, newly created objects inherit 738their parent directories' project ID if the parent's inherit flag is set 739.Pq via Nm chattr Sy [+-]P No or Nm zfs Cm project Fl s Ns | Ns Fl C . 740Otherwise, the new object's project ID will be zero. 741An object's project ID can be changed at any time by the owner 742.Pq or privileged user 743via 744.Nm chattr Fl p Ar prjid 745or 746.Nm zfs Cm project Fl p Ar prjid . 747.Pp 748This feature will become 749.Sy active 750as soon as it is enabled and will never return to being 751.Sy disabled . 752\*[remount-upgrade] 753. 754.feature com.delphix redaction_bookmarks no bookmarks extensible_dataset 755This feature enables the use of redacted 756.Nm zfs Cm send Ns s , 757which create redaction bookmarks storing the list of blocks 758redacted by the send that created them. 759For more information about redacted sends, see 760.Xr zfs-send 8 . 761. 762.feature com.delphix redacted_datasets no extensible_dataset 763This feature enables the receiving of redacted 764.Nm zfs Cm send 765streams, which create redacted datasets when received. 766These datasets are missing some of their blocks, 767and so cannot be safely mounted, and their contents cannot be safely read. 768For more information about redacted receives, see 769.Xr zfs-send 8 . 770. 771.feature com.datto resilver_defer yes 772This feature allows ZFS to postpone new resilvers if an existing one is already 773in progress. 774Without this feature, any new resilvers will cause the currently 775running one to be immediately restarted from the beginning. 776.Pp 777This feature becomes 778.Sy active 779once a resilver has been deferred, and returns to being 780.Sy enabled 781when the deferred resilver begins. 782. 783.feature org.illumos sha512 no extensible_dataset 784This feature enables the use of the SHA-512/256 truncated hash algorithm 785.Pq FIPS 180-4 786for checksum and dedup. 787The native 64-bit arithmetic of SHA-512 provides an approximate 50% 788performance boost over SHA-256 on 64-bit hardware 789and is thus a good minimum-change replacement candidate 790for systems where hash performance is important, 791but these systems cannot for whatever reason utilize the faster 792.Sy skein No and Sy edonr 793algorithms. 794.Pp 795.checksum-spiel sha512 796. 797.feature org.illumos skein no extensible_dataset 798This feature enables the use of the Skein hash algorithm for checksum and dedup. 799Skein is a high-performance secure hash algorithm that was a 800finalist in the NIST SHA-3 competition. 801It provides a very high security margin and high performance on 64-bit hardware 802.Pq 80% faster than SHA-256 . 803This implementation also utilizes the new salted checksumming 804functionality in ZFS, which means that the checksum is pre-seeded with a 805secret 256-bit random key 806.Pq stored on the pool 807before being fed the data block to be checksummed. 808Thus the produced checksums are unique to a given pool, 809preventing hash collision attacks on systems with dedup. 810.Pp 811.checksum-spiel skein 812. 813.feature com.delphix spacemap_histogram yes 814This features allows ZFS to maintain more information about how free space 815is organized within the pool. 816If this feature is 817.Sy enabled , 818it will be activated when a new space map object is created, or 819an existing space map is upgraded to the new format, 820and never returns back to being 821.Sy enabled . 822. 823.feature com.delphix spacemap_v2 yes 824This feature enables the use of the new space map encoding which 825consists of two words 826.Pq instead of one 827whenever it is advantageous. 828The new encoding allows space maps to represent large regions of 829space more efficiently on-disk while also increasing their maximum 830addressable offset. 831.Pp 832This feature becomes 833.Sy active 834once it is 835.Sy enabled , 836and never returns back to being 837.Sy enabled . 838. 839.feature org.zfsonlinux userobj_accounting yes extensible_dataset 840This feature allows administrators to account the object usage information 841by user and group. 842.Pp 843\*[instant-never] 844\*[remount-upgrade] 845. 846.feature org.openzfs zilsaxattr yes extensible_dataset 847This feature enables 848.Sy xattr Ns = Ns Sy sa 849extended attribute logging in the ZIL. 850If enabled, extended attribute changes 851.Pq both Sy xattrdir Ns = Ns Sy dir No and Sy xattr Ns = Ns Sy sa 852are guaranteed to be durable if either the dataset had 853.Sy sync Ns = Ns Sy always 854set at the time the changes were made, or 855.Xr sync 2 856is called on the dataset after the changes were made. 857.Pp 858This feature becomes 859.Sy active 860when a ZIL is created for at least one dataset and will be returned to the 861.Sy enabled 862state when it is destroyed for all datasets that use this feature. 863. 864.feature com.delphix zpool_checkpoint yes 865This feature enables the 866.Nm zpool Cm checkpoint 867command that can checkpoint the state of the pool 868at the time it was issued and later rewind back to it or discard it. 869.Pp 870This feature becomes 871.Sy active 872when the 873.Nm zpool Cm checkpoint 874command is used to checkpoint the pool. 875The feature will only return back to being 876.Sy enabled 877when the pool is rewound or the checkpoint has been discarded. 878. 879.feature org.freebsd zstd_compress no extensible_dataset 880.Sy zstd 881is a high-performance compression algorithm that features a 882combination of high compression ratios and high speed. 883Compared to 884.Sy gzip , 885.Sy zstd 886offers slightly better compression at much higher speeds. 887Compared to 888.Sy lz4 , 889.Sy zstd 890offers much better compression while being only modestly slower. 891Typically, 892.Sy zstd 893compression speed ranges from 250 to 500 MB/s per thread 894and decompression speed is over 1 GB/s per thread. 895.Pp 896When the 897.Sy zstd 898feature is set to 899.Sy enabled , 900the administrator can turn on 901.Sy zstd 902compression of any dataset using 903.Nm zfs Cm set Sy compress Ns = Ns Sy zstd Ar dset 904.Po see Xr zfs-set 8 Pc . 905This feature becomes 906.Sy active 907once a 908.Sy compress 909property has been set to 910.Sy zstd , 911and will return to being 912.Sy enabled 913once all filesystems that have ever had their 914.Sy compress 915property set to 916.Sy zstd 917are destroyed. 918.El 919. 920.Sh SEE ALSO 921.Xr zfs 8 , 922.Xr zpool 8 923