ZFS: Versioning

ZFS Versioning

Abstract:
Most operating systems support a type of file system to retain it's data. When newer versions of the file system are released, sometimes it is not clear to the user community. With ZFS, the ability to clearly see what the version exists and even a clear way to create older pool types for backwards compatibility and testing.

Article:
Bob Netherton at Oracle published a blog article recently discussing ZFS Versioning. It is well worth the read. Below are a few commands extracted from Bob's article.

Commands:
The "zpool" and "zfs" commands offer visibility to capabilities.

# zpool upgrade -v
This system is currently running ZFS pool version 31.

The following versions are supported:

VER  DESCRIPTION
---  --------------------------------------------------------
1   Initial ZFS version
2   Ditto blocks (replicated metadata)
3   Hot spares and double parity RAID-Z
4   zpool history
5   Compression using the gzip algorithm
6   bootfs pool property
7   Separate intent log devices
8   Delegated administration
9   refquota and refreservation properties
10  Cache devices
11  Improved scrub performance
12  Snapshot properties
13  snapused property
14  passthrough-x aclinherit
15  user/group space accounting
16  stmf property support
17  Triple-parity RAID-Z
18  Snapshot user holds
19  Log device removal
20  Compression using zle (zero-length encoding)
21  Deduplication
22  Received properties
23  Slim ZIL
24  System attributes
25  Improved scrub stats
26  Improved snapshot deletion performance
27  Improved snapshot creation performance
28  Multiple vdev replacements
29  RAID-Z/mirror hybrid allocator
30  Encryption
31  Improved 'zfs list' performance

For more information on a particular version, including supported releases,
see the ZFS Administration Guide.

# zfs upgrade -v
The following filesystem versions are supported:

VER  DESCRIPTION
---  --------------------------------------------------------
1   Initial ZFS filesystem version
2   Enhanced directory entries
3   Case insensitive and File system unique identifier (FUID)
4   userquota, groupquota properties
5   System attributes

For more information on a particular version, including supported releases,
see the ZFS Administration Guide.

Capabilities:
As of Solaris Update 6, the following lists the zpool and zfs versions.

Solaris Release         ZPOOL Version ZFS Version
Solaris 10 10/08 (u6)   10            3
Solaris 10 5/09 (u7)    10            3
Solaris 10 10/09 (u8    15            4
Solaris 10 9/10 (u9)    22            4
Solaris 10 8/11 (u10)   29            5
Solaris 11 11/11 (ga)   33            5

Showing Versions:
A test pool can be made, in order to show the versions.

# zpool create testpool testdisk

# zpool get version testpool
NAME      PROPERTY  VALUE    SOURCE
testpool  version   31       default

# zfs get version testpool
NAME      PROPERTY  VALUE    SOURCE
testpool  version   5        -

Creating Older Pools:
Older pools can be created and versions validated.

# zpool destroy testpool
# zpool create -o version=15 -O version=4 testpool testdisk
# zfs create testpool/data

# zpool get version testpool
NAME      PROPERTY  VALUE    SOURCE
testpool  version   15       local

# zfs get -r version testpool
NAME           PROPERTY  VALUE    SOURCE
testpool       version   4        -
testpool/data  version   4        -

Testing an Upgrade:
A version upgrade can be conducted and verified.

# zpool upgrade -V 29 testpool
This system is currently running ZFS pool version 31.

Successfully upgraded 'testpool' from version 15 to version 29

# zpool get version testpool
NAME      PROPERTY  VALUE    SOURCE
testpool  version   29       local

# zfs upgrade -V 5 testpool
1 filesystems upgraded

# zfs get -r version testpool
testpool       version   5        -
testpool/data  version   4        -

Upgrading Recursively:
While the base pool can be updated, it is most likely that file system under the pool needed to be upgraded. This can be done via the recursive option.

# zfs upgrade -V 5 -r testpool
1 filesystems upgraded
1 filesystems already at this version

# zfs get -r version testpool
NAME           PROPERTY  VALUE    SOURCE
testpool       version   5        -
testpool/data  version   5        -