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, 2023, 2024, Klara, Inc. 18.\" Copyright (c) 2019, Allan Jude 19.\" Copyright (c) 2021, Colm Buckley <colm@tuatha.org> 20.\" 21.Dd October 2, 2024 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 versions from v2.12 onwards. 222allocation_classes 223async_destroy 224block_cloning 225bookmarks 226device_rebuild 227embedded_data 228empty_bpobj 229enabled_txg 230extensible_dataset 231filesystem_limits 232hole_birth 233large_blocks 234livelist 235log_spacemap 236lz4_compress 237project_quota 238resilver_defer 239spacemap_histogram 240spacemap_v2 241userobj_accounting 242zilsaxattr 243zpool_checkpoint 244 245.No example# Nm cat Pa /usr/share/zfs/compatibility.d/grub2-2.06 246# Features which are supported by GRUB2 versions prior to v2.12. 247# 248# GRUB is not able to detect ZFS pool if snaphsot of top level boot pool 249# is created. This issue is observed with GRUB versions before v2.12 if 250# extensible_dataset feature is enabled on ZFS boot pool. 251# 252# This file lists all read-only comaptible features except 253# extensible_dataset and any other feature that depends on it. 254# 255allocation_classes 256async_destroy 257block_cloning 258device_rebuild 259embedded_data 260empty_bpobj 261enabled_txg 262hole_birth 263log_spacemap 264lz4_compress 265resilver_defer 266spacemap_histogram 267spacemap_v2 268zpool_checkpoint 269 270.No example# Nm zpool Cm create Fl o Sy compatibility Ns = Ns Ar grub2 Ar bootpool Ar vdev 271.Ed 272.Pp 273See 274.Xr zpool-create 8 275and 276.Xr zpool-upgrade 8 277for more information on how these commands are affected by feature sets. 278. 279.de feature 280.It Sy \\$2 281.Bl -tag -compact -width "READ-ONLY COMPATIBLE" 282.It GUID 283.Sy \\$1:\\$2 284.if !"\\$4"" \{\ 285.It DEPENDENCIES 286\fB\\$4\fP\c 287.if !"\\$5"" , \fB\\$5\fP\c 288.if !"\\$6"" , \fB\\$6\fP\c 289.if !"\\$7"" , \fB\\$7\fP\c 290.if !"\\$8"" , \fB\\$8\fP\c 291.if !"\\$9"" , \fB\\$9\fP\c 292.\} 293.It READ-ONLY COMPATIBLE 294\\$3 295.El 296.Pp 297.. 298. 299.ds instant-never \ 300.No This feature becomes Sy active No as soon as it is enabled \ 301and will never return to being Sy enabled . 302. 303.ds remount-upgrade \ 304.No Each filesystem will be upgraded automatically when remounted, \ 305or when a new file is created under that filesystem. \ 306The upgrade can also be triggered on filesystems via \ 307Nm zfs Cm set Sy version Ns = Ns Sy current Ar fs . \ 308No The upgrade process runs in the background and may take a while to complete \ 309for filesystems containing large amounts of files . 310. 311.de checksum-spiel 312When the 313.Sy \\$1 314feature is set to 315.Sy enabled , 316the administrator can turn on the 317.Sy \\$1 318checksum on any dataset using 319.Nm zfs Cm set Sy checksum Ns = Ns Sy \\$1 Ar dset 320.Po see Xr zfs-set 8 Pc . 321This feature becomes 322.Sy active 323once a 324.Sy checksum 325property has been set to 326.Sy \\$1 , 327and will return to being 328.Sy enabled 329once all filesystems that have ever had their checksum set to 330.Sy \\$1 331are destroyed. 332.. 333. 334.Sh FEATURES 335The following features are supported on this system: 336.Bl -tag -width Ds 337.feature org.zfsonlinux allocation_classes yes 338This feature enables support for separate allocation classes. 339.Pp 340This feature becomes 341.Sy active 342when a dedicated allocation class vdev 343.Pq dedup or special 344is created with the 345.Nm zpool Cm create No or Nm zpool Cm add No commands . 346With device removal, it can be returned to the 347.Sy enabled 348state if all the dedicated allocation class vdevs are removed. 349. 350.feature com.delphix async_destroy yes 351Destroying a file system requires traversing all of its data in order to 352return its used space to the pool. 353Without 354.Sy async_destroy , 355the file system is not fully removed until all space has been reclaimed. 356If the destroy operation is interrupted by a reboot or power outage, 357the next attempt to open the pool will need to complete the destroy 358operation synchronously. 359.Pp 360When 361.Sy async_destroy 362is enabled, the file system's data will be reclaimed by a background process, 363allowing the destroy operation to complete 364without traversing the entire file system. 365The background process is able to resume 366interrupted destroys after the pool has been opened, eliminating the need 367to finish interrupted destroys as part of the open operation. 368The amount of space remaining to be reclaimed by the background process 369is available through the 370.Sy freeing 371property. 372.Pp 373This feature is only 374.Sy active 375while 376.Sy freeing 377is non-zero. 378. 379.feature org.openzfs blake3 no extensible_dataset 380This feature enables the use of the BLAKE3 hash algorithm for checksum and 381dedup. 382BLAKE3 is a secure hash algorithm focused on high performance. 383.Pp 384.checksum-spiel blake3 385. 386.feature com.fudosecurity block_cloning yes 387When this feature is enabled ZFS will use block cloning for operations like 388.Fn copy_file_range 2 . 389Block cloning allows to create multiple references to a single block. 390It is much faster than copying the data (as the actual data is neither read nor 391written) and takes no additional space. 392Blocks can be cloned across datasets under some conditions (like equal 393.Nm recordsize , 394the same master encryption key, etc.). 395ZFS tries its best to clone across datasets including encrypted ones. 396This is limited for various (nontrivial) reasons depending on the OS 397and/or ZFS internals. 398.Pp 399This feature becomes 400.Sy active 401when first block is cloned. 402When the last cloned block is freed, it goes back to the enabled state. 403.feature com.delphix bookmarks yes extensible_dataset 404This feature enables use of the 405.Nm zfs Cm bookmark 406command. 407.Pp 408This feature is 409.Sy active 410while any bookmarks exist in the pool. 411All bookmarks in the pool can be listed by running 412.Nm zfs Cm list Fl t Sy bookmark Fl r Ar poolname . 413. 414.feature com.datto bookmark_v2 no bookmark extensible_dataset 415This feature enables the creation and management of larger bookmarks which are 416needed for other features in ZFS. 417.Pp 418This feature becomes 419.Sy active 420when a v2 bookmark is created and will be returned to the 421.Sy enabled 422state when all v2 bookmarks are destroyed. 423. 424.feature com.delphix bookmark_written no bookmark extensible_dataset bookmark_v2 425This feature enables additional bookmark accounting fields, enabling the 426.Sy written Ns # Ns Ar bookmark 427property 428.Pq space written since a bookmark 429and estimates of send stream sizes for incrementals from bookmarks. 430.Pp 431This feature becomes 432.Sy active 433when a bookmark is created and will be 434returned to the 435.Sy enabled 436state when all bookmarks with these fields are destroyed. 437. 438.feature org.openzfs device_rebuild yes 439This feature enables the ability for the 440.Nm zpool Cm attach 441and 442.Nm zpool Cm replace 443commands to perform sequential reconstruction 444.Pq instead of healing reconstruction 445when resilvering. 446.Pp 447Sequential reconstruction resilvers a device in LBA order without immediately 448verifying the checksums. 449Once complete, a scrub is started, which then verifies the checksums. 450This approach allows full redundancy to be restored to the pool 451in the minimum amount of time. 452This two-phase approach will take longer than a healing resilver 453when the time to verify the checksums is included. 454However, unless there is additional pool damage, 455no checksum errors should be reported by the scrub. 456This feature is incompatible with raidz configurations. 457. 458This feature becomes 459.Sy active 460while a sequential resilver is in progress, and returns to 461.Sy enabled 462when the resilver completes. 463. 464.feature com.delphix device_removal no 465This feature enables the 466.Nm zpool Cm remove 467command to remove top-level vdevs, 468evacuating them to reduce the total size of the pool. 469.Pp 470This feature becomes 471.Sy active 472when the 473.Nm zpool Cm remove 474command is used 475on a top-level vdev, and will never return to being 476.Sy enabled . 477. 478.feature org.openzfs draid no 479This feature enables use of the 480.Sy draid 481vdev type. 482dRAID is a variant of RAID-Z which provides integrated distributed 483hot spares that allow faster resilvering while retaining the benefits of RAID-Z. 484Data, parity, and spare space are organized in redundancy groups 485and distributed evenly over all of the devices. 486.Pp 487This feature becomes 488.Sy active 489when creating a pool which uses the 490.Sy draid 491vdev type, or when adding a new 492.Sy draid 493vdev to an existing pool. 494. 495.feature org.illumos edonr no extensible_dataset 496This feature enables the use of the Edon-R hash algorithm for checksum, 497including for nopwrite 498.Po if compression is also enabled, an overwrite of 499a block whose checksum matches the data being written will be ignored 500.Pc . 501In an abundance of caution, Edon-R requires verification when used with 502dedup: 503.Nm zfs Cm set Sy dedup Ns = Ns Sy edonr , Ns Sy verify 504.Po see Xr zfs-set 8 Pc . 505.Pp 506Edon-R is a very high-performance hash algorithm that was part 507of the NIST SHA-3 competition. 508It provides extremely high hash performance 509.Pq over 350% faster than SHA-256 , 510but was not selected because of its unsuitability 511as a general purpose secure hash algorithm. 512This implementation utilizes the new salted checksumming functionality 513in ZFS, which means that the checksum is pre-seeded with a secret 514256-bit random key 515.Pq stored on the pool 516before being fed the data block to be checksummed. 517Thus the produced checksums are unique to a given pool, 518preventing hash collision attacks on systems with dedup. 519.Pp 520.checksum-spiel edonr 521. 522.feature com.delphix embedded_data no 523This feature improves the performance and compression ratio of 524highly-compressible blocks. 525Blocks whose contents can compress to 112 bytes 526or smaller can take advantage of this feature. 527.Pp 528When this feature is enabled, the contents of highly-compressible blocks are 529stored in the block 530.Dq pointer 531itself 532.Po a misnomer in this case, as it contains 533the compressed data, rather than a pointer to its location on disk 534.Pc . 535Thus the space of the block 536.Pq one sector, typically 512 B or 4 KiB 537is saved, and no additional I/O is needed to read and write the data block. 538. 539\*[instant-never] 540. 541.feature com.delphix empty_bpobj yes 542This feature increases the performance of creating and using a large 543number of snapshots of a single filesystem or volume, and also reduces 544the disk space required. 545.Pp 546When there are many snapshots, each snapshot uses many Block Pointer 547Objects 548.Pq bpobjs 549to track blocks associated with that snapshot. 550However, in common use cases, most of these bpobjs are empty. 551This feature allows us to create each bpobj on-demand, 552thus eliminating the empty bpobjs. 553.Pp 554This feature is 555.Sy active 556while there are any filesystems, volumes, 557or snapshots which were created after enabling this feature. 558. 559.feature com.delphix enabled_txg yes 560Once this feature is enabled, ZFS records the transaction group number 561in which new features are enabled. 562This has no user-visible impact, but other features may depend on this feature. 563.Pp 564This feature becomes 565.Sy active 566as soon as it is enabled and will never return to being 567.Sy enabled . 568. 569.feature com.datto encryption no bookmark_v2 extensible_dataset 570This feature enables the creation and management of natively encrypted datasets. 571.Pp 572This feature becomes 573.Sy active 574when an encrypted dataset is created and will be returned to the 575.Sy enabled 576state when all datasets that use this feature are destroyed. 577. 578.feature com.klarasystems fast_dedup yes 579This feature allows more advanced deduplication features to be enabled on new 580dedup tables. 581.Pp 582This feature will be 583.Sy active 584when the first deduplicated block is written after a new dedup table is created 585(ie after a new pool creation, or new checksum used on a dataset with 586.Sy dedup 587enabled). 588It will be returned to the 589.Sy enabled 590state when all deduplicated blocks using it are freed. 591. 592.feature com.delphix extensible_dataset no 593This feature allows more flexible use of internal ZFS data structures, 594and exists for other features to depend on. 595.Pp 596This feature will be 597.Sy active 598when the first dependent feature uses it, and will be returned to the 599.Sy enabled 600state when all datasets that use this feature are destroyed. 601. 602.feature com.joyent filesystem_limits yes extensible_dataset 603This feature enables filesystem and snapshot limits. 604These limits can be used to control how many filesystems and/or snapshots 605can be created at the point in the tree on which the limits are set. 606.Pp 607This feature is 608.Sy active 609once either of the limit properties has been set on a dataset 610and will never return to being 611.Sy enabled . 612. 613.feature com.delphix head_errlog no 614This feature enables the upgraded version of errlog, which required an on-disk 615error log format change. 616Now the error log of each head dataset is stored separately in the zap object 617and keyed by the head id. 618With this feature enabled, every dataset affected by an error block is listed 619in the output of 620.Nm zpool Cm status . 621In case of encrypted filesystems with unloaded keys we are unable to check 622their snapshots or clones for errors and these will not be reported. 623An "access denied" error will be reported. 624.Pp 625\*[instant-never] 626. 627.feature com.delphix hole_birth no enabled_txg 628This feature has/had bugs, the result of which is that, if you do a 629.Nm zfs Cm send Fl i 630.Pq or Fl R , No since it uses Fl i 631from an affected dataset, the receiving party will not see any checksum 632or other errors, but the resulting destination snapshot 633will not match the source. 634Its use by 635.Nm zfs Cm send Fl i 636has been disabled by default 637.Po 638see 639.Sy send_holes_without_birth_time 640in 641.Xr zfs 4 642.Pc . 643.Pp 644This feature improves performance of incremental sends 645.Pq Nm zfs Cm send Fl i 646and receives for objects with many holes. 647The most common case of hole-filled objects is zvols. 648.Pp 649An incremental send stream from snapshot 650.Sy A No to snapshot Sy B 651contains information about every block that changed between 652.Sy A No and Sy B . 653Blocks which did not change between those snapshots can be 654identified and omitted from the stream using a piece of metadata called 655the 656.Dq block birth time , 657but birth times are not recorded for holes 658.Pq blocks filled only with zeroes . 659Since holes created after 660.Sy A No cannot be distinguished from holes created before Sy A , 661information about every hole in the entire filesystem or zvol 662is included in the send stream. 663.Pp 664For workloads where holes are rare this is not a problem. 665However, when incrementally replicating filesystems or zvols with many holes 666.Pq for example a zvol formatted with another filesystem 667a lot of time will be spent sending and receiving unnecessary information 668about holes that already exist on the receiving side. 669.Pp 670Once the 671.Sy hole_birth 672feature has been enabled the block birth times 673of all new holes will be recorded. 674Incremental sends between snapshots created after this feature is enabled 675will use this new metadata to avoid sending information about holes that 676already exist on the receiving side. 677.Pp 678\*[instant-never] 679. 680.feature org.open-zfs large_blocks no extensible_dataset 681This feature allows the record size on a dataset to be set larger than 128 KiB. 682.Pp 683This feature becomes 684.Sy active 685once a dataset contains a file with a block size larger than 128 KiB, 686and will return to being 687.Sy enabled 688once all filesystems that have ever had their recordsize larger than 128 KiB 689are destroyed. 690. 691.feature org.zfsonlinux large_dnode no extensible_dataset 692This feature allows the size of dnodes in a dataset to be set larger than 512 B. 693. 694This feature becomes 695.Sy active 696once a dataset contains an object with a dnode larger than 512 B, 697which occurs as a result of setting the 698.Sy dnodesize 699dataset property to a value other than 700.Sy legacy . 701The feature will return to being 702.Sy enabled 703once all filesystems that have ever contained a dnode larger than 512 B 704are destroyed. 705Large dnodes allow more data to be stored in the bonus buffer, 706thus potentially improving performance by avoiding the use of spill blocks. 707. 708.feature com.klarasystems large_microzap yes extensible_dataset large_blocks 709This feature allows "micro" ZAPs to grow larger than 128 KiB without being 710upgraded to "fat" ZAPs. 711.Pp 712This feature becomes 713.Sy active 714the first time a micro ZAP grows larger than 128KiB. 715It will only be returned to the 716.Sy enabled 717state when all datasets that ever had a large micro ZAP are destroyed. 718.Pp 719Note that even when this feature is enabled, micro ZAPs cannot grow larger 720than 128 KiB without also changing the 721.Sy zap_micro_max_size 722module parameter. 723See 724.Xr zfs 4 . 725. 726.feature com.delphix livelist yes extensible_dataset 727This feature allows clones to be deleted faster than the traditional method 728when a large number of random/sparse writes have been made to the clone. 729All blocks allocated and freed after a clone is created are tracked by the 730the clone's livelist which is referenced during the deletion of the clone. 731The feature is activated when a clone is created and remains 732.Sy active 733until all clones have been destroyed. 734. 735.feature com.delphix log_spacemap yes com.delphix:spacemap_v2 736This feature improves performance for heavily-fragmented pools, 737especially when workloads are heavy in random-writes. 738It does so by logging all the metaslab changes on a single spacemap every TXG 739instead of scattering multiple writes to all the metaslab spacemaps. 740.Pp 741\*[instant-never] 742. 743.feature org.zfsonlinux longname no extensible_dataset 744This feature allows creating files and directories with name up to 1023 bytes 745in length. 746A new dataset property 747.Sy longname 748is also introduced to toggle longname support for each dataset individually. 749This property can be disabled even if it contains longname files. 750In such case, new file cannot be created with longname but existing longname 751files can still be looked up. 752.Pp 753This feature becomes 754.Sy active 755when a file name greater than 255 is created in a dataset, and returns to 756being 757.Sy enabled 758when all such datasets are destroyed. 759. 760.feature org.illumos lz4_compress no 761.Sy lz4 762is a high-performance real-time compression algorithm that 763features significantly faster compression and decompression as well as a 764higher compression ratio than the older 765.Sy lzjb 766compression. 767Typically, 768.Sy lz4 769compression is approximately 50% faster on compressible data and 200% faster 770on incompressible data than 771.Sy lzjb . 772It is also approximately 80% faster on decompression, 773while giving approximately a 10% better compression ratio. 774.Pp 775When the 776.Sy lz4_compress 777feature is set to 778.Sy enabled , 779the administrator can turn on 780.Sy lz4 781compression on any dataset on the pool using the 782.Xr zfs-set 8 783command. 784All newly written metadata will be compressed with the 785.Sy lz4 786algorithm. 787.Pp 788\*[instant-never] 789. 790.feature com.joyent multi_vdev_crash_dump no 791This feature allows a dump device to be configured with a pool comprised 792of multiple vdevs. 793Those vdevs may be arranged in any mirrored or raidz configuration. 794.Pp 795When the 796.Sy multi_vdev_crash_dump 797feature is set to 798.Sy enabled , 799the administrator can use 800.Xr dumpadm 8 801to configure a dump device on a pool comprised of multiple vdevs. 802.Pp 803Under 804.Fx 805and Linux this feature is unused, but registered for compatibility. 806New pools created on these systems will have the feature 807.Sy enabled 808but will never transition to 809.Sy active , 810as this functionality is not required for crash dump support. 811Existing pools where this feature is 812.Sy active 813can be imported. 814. 815.feature com.delphix obsolete_counts yes device_removal 816This feature is an enhancement of 817.Sy device_removal , 818which will over time reduce the memory used to track removed devices. 819When indirect blocks are freed or remapped, 820we note that their part of the indirect mapping is 821.Dq obsolete 822– no longer needed. 823.Pp 824This feature becomes 825.Sy active 826when the 827.Nm zpool Cm remove 828command is used on a top-level vdev, and will never return to being 829.Sy enabled . 830. 831.feature org.zfsonlinux project_quota yes extensible_dataset 832This feature allows administrators to account the spaces and objects usage 833information against the project identifier 834.Pq ID . 835.Pp 836The project ID is an object-based attribute. 837When upgrading an existing filesystem, 838objects without a project ID will be assigned a zero project ID. 839When this feature is enabled, newly created objects inherit 840their parent directories' project ID if the parent's inherit flag is set 841.Pq via Nm chattr Sy [+-]P No or Nm zfs Cm project Fl s Ns | Ns Fl C . 842Otherwise, the new object's project ID will be zero. 843An object's project ID can be changed at any time by the owner 844.Pq or privileged user 845via 846.Nm chattr Fl p Ar prjid 847or 848.Nm zfs Cm project Fl p Ar prjid . 849.Pp 850This feature will become 851.Sy active 852as soon as it is enabled and will never return to being 853.Sy disabled . 854\*[remount-upgrade] 855. 856.feature org.openzfs raidz_expansion no none 857This feature enables the 858.Nm zpool Cm attach 859subcommand to attach a new device to a RAID-Z group, expanding the total 860amount usable space in the pool. 861See 862.Xr zpool-attach 8 . 863. 864.feature com.delphix redaction_bookmarks no bookmarks extensible_dataset 865This feature enables the use of redacted 866.Nm zfs Cm send Ns s , 867which create redaction bookmarks storing the list of blocks 868redacted by the send that created them. 869For more information about redacted sends, see 870.Xr zfs-send 8 . 871. 872.feature com.delphix redacted_datasets no extensible_dataset 873This feature enables the receiving of redacted 874.Nm zfs Cm send 875streams, which create redacted datasets when received. 876These datasets are missing some of their blocks, 877and so cannot be safely mounted, and their contents cannot be safely read. 878For more information about redacted receives, see 879.Xr zfs-send 8 . 880. 881.feature com.delphix redaction_list_spill no redaction_bookmarks 882This feature enables the redaction list created by zfs redact to store 883many more entries. 884It becomes 885.Sy active 886when a redaction list is created with more than 36 entries, 887and returns to being 888.Sy enabled 889when no long redaction lists remain in the pool. 890For more information about redacted sends, see 891.Xr zfs-send 8 . 892. 893.feature com.datto resilver_defer yes 894This feature allows ZFS to postpone new resilvers if an existing one is already 895in progress. 896Without this feature, any new resilvers will cause the currently 897running one to be immediately restarted from the beginning. 898.Pp 899This feature becomes 900.Sy active 901once a resilver has been deferred, and returns to being 902.Sy enabled 903when the deferred resilver begins. 904. 905.feature org.illumos sha512 no extensible_dataset 906This feature enables the use of the SHA-512/256 truncated hash algorithm 907.Pq FIPS 180-4 908for checksum and dedup. 909The native 64-bit arithmetic of SHA-512 provides an approximate 50% 910performance boost over SHA-256 on 64-bit hardware 911and is thus a good minimum-change replacement candidate 912for systems where hash performance is important, 913but these systems cannot for whatever reason utilize the faster 914.Sy skein No and Sy edonr 915algorithms. 916.Pp 917.checksum-spiel sha512 918. 919.feature org.illumos skein no extensible_dataset 920This feature enables the use of the Skein hash algorithm for checksum and dedup. 921Skein is a high-performance secure hash algorithm that was a 922finalist in the NIST SHA-3 competition. 923It provides a very high security margin and high performance on 64-bit hardware 924.Pq 80% faster than SHA-256 . 925This implementation also utilizes the new salted checksumming 926functionality in ZFS, which means that the checksum is pre-seeded with a 927secret 256-bit random key 928.Pq stored on the pool 929before being fed the data block to be checksummed. 930Thus the produced checksums are unique to a given pool, 931preventing hash collision attacks on systems with dedup. 932.Pp 933.checksum-spiel skein 934. 935.feature com.delphix spacemap_histogram yes 936This features allows ZFS to maintain more information about how free space 937is organized within the pool. 938If this feature is 939.Sy enabled , 940it will be activated when a new space map object is created, or 941an existing space map is upgraded to the new format, 942and never returns back to being 943.Sy enabled . 944. 945.feature com.delphix spacemap_v2 yes 946This feature enables the use of the new space map encoding which 947consists of two words 948.Pq instead of one 949whenever it is advantageous. 950The new encoding allows space maps to represent large regions of 951space more efficiently on-disk while also increasing their maximum 952addressable offset. 953.Pp 954This feature becomes 955.Sy active 956once it is 957.Sy enabled , 958and never returns back to being 959.Sy enabled . 960. 961.feature org.zfsonlinux userobj_accounting yes extensible_dataset 962This feature allows administrators to account the object usage information 963by user and group. 964.Pp 965\*[instant-never] 966\*[remount-upgrade] 967. 968.feature com.klarasystems vdev_zaps_v2 no 969This feature creates a ZAP object for the root vdev. 970.Pp 971This feature becomes active after the next 972.Nm zpool Cm import 973or 974.Nm zpool reguid . 975. 976Properties can be retrieved or set on the root vdev using 977.Nm zpool Cm get 978and 979.Nm zpool Cm set 980with 981.Sy root 982as the vdev name which is an alias for 983.Sy root-0 . 984.feature org.openzfs zilsaxattr yes extensible_dataset 985This feature enables 986.Sy xattr Ns = Ns Sy sa 987extended attribute logging in the ZIL. 988If enabled, extended attribute changes 989.Pq both Sy xattrdir Ns = Ns Sy dir No and Sy xattr Ns = Ns Sy sa 990are guaranteed to be durable if either the dataset had 991.Sy sync Ns = Ns Sy always 992set at the time the changes were made, or 993.Xr sync 2 994is called on the dataset after the changes were made. 995.Pp 996This feature becomes 997.Sy active 998when a ZIL is created for at least one dataset and will be returned to the 999.Sy enabled 1000state when it is destroyed for all datasets that use this feature. 1001. 1002.feature com.delphix zpool_checkpoint yes 1003This feature enables the 1004.Nm zpool Cm checkpoint 1005command that can checkpoint the state of the pool 1006at the time it was issued and later rewind back to it or discard it. 1007.Pp 1008This feature becomes 1009.Sy active 1010when the 1011.Nm zpool Cm checkpoint 1012command is used to checkpoint the pool. 1013The feature will only return back to being 1014.Sy enabled 1015when the pool is rewound or the checkpoint has been discarded. 1016. 1017.feature org.freebsd zstd_compress no extensible_dataset 1018.Sy zstd 1019is a high-performance compression algorithm that features a 1020combination of high compression ratios and high speed. 1021Compared to 1022.Sy gzip , 1023.Sy zstd 1024offers slightly better compression at much higher speeds. 1025Compared to 1026.Sy lz4 , 1027.Sy zstd 1028offers much better compression while being only modestly slower. 1029Typically, 1030.Sy zstd 1031compression speed ranges from 250 to 500 MB/s per thread 1032and decompression speed is over 1 GB/s per thread. 1033.Pp 1034When the 1035.Sy zstd 1036feature is set to 1037.Sy enabled , 1038the administrator can turn on 1039.Sy zstd 1040compression of any dataset using 1041.Nm zfs Cm set Sy compress Ns = Ns Sy zstd Ar dset 1042.Po see Xr zfs-set 8 Pc . 1043This feature becomes 1044.Sy active 1045once a 1046.Sy compress 1047property has been set to 1048.Sy zstd , 1049and will return to being 1050.Sy enabled 1051once all filesystems that have ever had their 1052.Sy compress 1053property set to 1054.Sy zstd 1055are destroyed. 1056.El 1057. 1058.Sh SEE ALSO 1059.Xr zfs 8 , 1060.Xr zpool 8 1061