Difference between revisions of "Feature Flags"

From OpenZFS
Jump to: navigation, search
m (Fix OmniOS version)
(Feature Flags Implementation: Add FreeBSD -CURRENT, and fix link to mm@'s site)
Line 12: Line 12:
 
{| class="wikitable"
 
{| class="wikitable"
 
!Feature flag
 
!Feature flag
!colspan=3|FreeBSD
+
!colspan=4|FreeBSD
 
!ZFS on Linux
 
!ZFS on Linux
 
!OpenZFS OSX
 
!OpenZFS OSX
Line 21: Line 21:
 
| 9.3
 
| 9.3
 
| 10.1
 
| 10.1
 +
| r283009
 
| 0.6.4
 
| 0.6.4
 
| 1.3.1
 
| 1.3.1
Line 26: Line 27:
 
|-
 
|-
 
!async_destroy
 
!async_destroy
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 34: Line 36:
 
|-
 
|-
 
!empty_bpobj
 
!empty_bpobj
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 42: Line 45:
 
|-
 
|-
 
!lz4_compress
 
!lz4_compress
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 51: Line 55:
 
!multi_vdev_crash_dump
 
!multi_vdev_crash_dump
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 59: Line 64:
 
!spacemap_histogram
 
!spacemap_histogram
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 67: Line 73:
 
!enabled_txg
 
!enabled_txg
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 75: Line 82:
 
!hole_birth
 
!hole_birth
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 83: Line 91:
 
!extensible_dataset
 
!extensible_dataset
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 92: Line 101:
 
|no
 
|no
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 99: Line 109:
 
!bookmarks
 
!bookmarks
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 107: Line 118:
 
!filesystem_limits
 
!filesystem_limits
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
 
|style="background-color:lightgreen"|yes
Line 117: Line 129:
 
|no
 
|no
 
|no
 
|no
 +
|style="background-color:lightgreen"|yes
 
|no
 
|no
 
|no
 
|no
Line 126: Line 139:
 
* yes = implemented
 
* yes = implemented
  
Table source: [http://blog.vx.sk/archives/44-OpenZFS-Feature-Flags-Compatibility-Matrix.html|''OpenZFS Feature Flags Compatibility Matrix''] at blog.vx.sk
+
Table source: [http://blog.vx.sk/archives/44-OpenZFS-Feature-Flags-Compatibility-Matrix.html ''OpenZFS Feature Flags Compatibility Matrix''] at blog.vx.sk

Revision as of 22:32, 4 June 2015

Originally the ZFS on-disk format was versioned with a single number that was increased whenever a new on-disk format change was introduced. This worked well when a single entity controlled the development of ZFS; however, in the more distributed development model of OpenZFS a single version number is not ideal. Every OpenZFS implementation would need to agree on every change to the on-disk format.

One of the first OpenZFS projects was a new versioning system called "feature flags" that tags on-disk format changes with unique names. The system supports both completely independent format changes, as well as format changes that depend on each other. A pool's on-disk format is portable between OpenZFS implementations as long as all of the feature flags in use by the pool are supported by both implementations.

For more details see these slides (Jan 2012) and zpool-features(5) (illumos) or zpool-features(7) (FreeBSD).

For greatest compatibility, features that are exclusive (when enabled) should be periodically ported to all other distributions.

Feature Flags Implementation

The current state of OpenZFS feature flags implementation is in the following table.

Feature flag FreeBSD ZFS on Linux OpenZFS OSX OmniOS
8.4 9.3 10.1 r283009 0.6.4 1.3.1 r151014
async_destroy yes yes yes yes yes yes yes
empty_bpobj yes yes yes yes yes yes yes
lz4_compress yes yes yes yes yes yes yes
multi_vdev_crash_dump no yes yes yes no no yes
spacemap_histogram no yes yes yes yes yes yes
enabled_txg no yes yes yes yes yes yes
hole_birth no yes yes yes yes yes yes
extensible_dataset no yes yes yes yes yes yes
embedded_data no no yes yes yes yes yes
bookmarks no yes yes yes yes yes yes
filesystem_limits no yes yes yes no no yes
large_blocks no no no yes no no yes

Table legend

  • no = not implemented
  • yes = implemented

Table source: OpenZFS Feature Flags Compatibility Matrix at blog.vx.sk