Feature Flags

ZFS on-disk formats were originally versioned with a single number, which increased whenever the format changed. The numbered approach was suitable when development of ZFS was driven by a single organisation.

For distributed development of OpenZFS, version numbering was unsuitable. Any change to the number would have required agreement, across all implementations, of each change to the on-disk format.

OpenZFS feature flags – an alternative to traditional version numbering – allow a uniquely named pool property for each change to the on-disk format. This approach supports:

format changes that are independent
format changes that depend on each other.

Compatibility

Where all features that are used by a pool are supported by multiple implementations of OpenZFS, the on-disk format is portable across those implementations.

Features that are exclusive when enabled should be periodically ported to all distributions.

Reference materials

ZFS Feature Flags (Christopher Siden, 2012-01, in the Internet Archive Wayback Machine) in particular: “… Legacy version numbers still exist for pool versions 1-28 …”.

zpool-features(7) man page - OpenZFS

zpool-features (5) – illumos

Feature flags implementation per OS

ZFS Feature Matrix

Feature Flag	Read-Only Compatible	OpenZFS (Linux, FreeBSD 13+)						FreeBSD pre OpenZFS		Illumos	Joyent	NetBSD		Nexenta		OmniOS CE			OpenZFS on OS X
Feature Flag	Read-Only Compatible	0.6.5.11	0.7.13	0.8.6	2.0.7	2.1.12	master	12.1.0	12.2.0	master	master	9.3	main	4.0.5-FP	master	r151044	r151046	master	2.0.1	2.1.0	2.1.0-rc4	master
org.zfsonlinux:allocation_classes	yes	no	no	yes	yes	yes	yes	no	yes	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:async_destroy	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
org.openzfs:blake3	no	no	no	no	no	no	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no
com.fudosecurity:block_cloning	yes	no	no	no	no	no	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no
com.datto:bookmark_v2	no	no	no	yes	yes	yes	yes	no	no	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:bookmark_written	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:bookmarks	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.nexenta:class_of_storage	yes	no	no	no	no	no	no	no	no	no	no	no	no	yes	yes	no	no	no	no	no	no	no
org.openzfs:device_rebuild	yes	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:device_removal	no	no	no	yes	yes	yes	yes	yes	yes	yes	yes	no	no	no	yes	yes	yes	yes	yes	yes	yes	yes
org.openzfs:draid	no	no	no	no	no	yes	yes	no	no	no	no	no	no	no	no	no	no	no	yes	yes	yes	yes
org.illumos:edonr	no	yes¹	yes¹	yes¹	yes¹	yes¹	yes	no	no	yes	yes	no	no	no	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:embedded_data	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:empty_bpobj	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:enabled_txg	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.datto:encryption	no	no	no	yes	yes	yes	yes	no	no	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:extensible_dataset	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.joyent:filesystem_limits	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:head_errlog	no	no	no	no	no	no	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no
com.delphix:hole_birth	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
org.open-zfs:large_blocks	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	yes	yes	yes	yes	yes	yes
org.zfsonlinux:large_dnode	no	no	yes	yes	yes	yes	yes	no	yes	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:livelist	yes	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:log_spacemap	yes	no	no	no	yes	yes	yes	no	no	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
org.illumos:lz4_compress	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.nexenta:meta_devices	yes	no	no	no	no	no	no	no	no	no	no	no	no	yes	yes	no	no	no	no	no	no	no
com.joyent:multi_vdev_crash_dump	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:obsolete_counts	yes	no	no	yes	yes	yes	yes	yes	yes	yes	yes	no	no	no	yes	yes	yes	yes	yes	yes	yes	yes
org.zfsonlinux:project_quota	yes	no	no	yes	yes	yes	yes	no	no	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
com.delphix:redacted_datasets	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:redaction_bookmarks	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	no	no	no	yes	yes	yes	yes
com.delphix:redaction_list_spill	no	no	no	no	no	no	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no
com.datto:resilver_defer	yes	no	no	yes	yes	yes	yes	no	no	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
org.illumos:sha512	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	yes	yes	yes	yes	yes	yes
org.illumos:skein	no	no	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	no	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:spacemap_histogram	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes	yes
com.delphix:spacemap_v2	yes	no	no	yes	yes	yes	yes	yes	yes	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
org.zfsonlinux:userobj_accounting	yes	no	yes	yes	yes	yes	yes	no	no	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
com.nexenta:vdev_properties	yes	no	no	no	no	no	no	no	no	no	no	no	no	yes	yes	no	no	no	no	no	no	no
com.klarasystems:vdev_zaps_v2	no	no	no	no	no	no	yes	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no
com.nexenta:wbc	no	no	no	no	no	no	no	no	no	no	no	no	no	no	yes	no	no	no	no	no	no	no
org.openzfs:zilsaxattr	yes	no	no	no	no	no	yes	no	no	yes	yes	no	no	no	no	yes	yes	yes	no	no	no	no
com.delphix:zpool_checkpoint	yes	no	no	yes	yes	yes	yes	yes	yes	yes	yes	no	no	no	no	yes	yes	yes	yes	yes	yes	yes
org.freebsd:zstd_compress	no	no	no	no	yes	yes	yes	no	no	no	no	no	no	no	no	no	no	no	yes	yes	yes	yes

Notes:

Edonr support was not enabled in FreeBSD with OpenZFS up to 2.1 release included

Table generates by parsing manpages for feature flags, and is entirely dependent on good, accurate documentation.
Last updated on 2023-09-11T16:34:36.243163Z using compatibility_matrix.py.