I’m running ZFS on Fedora 23 and I notice that there’re new features which can be enabled in the existing pool.

# zpool status
  pool: tank
 state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
        still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
        the pool may no longer be accessible by software that does not support
        the features. See zpool-features(5) for details.
  scan: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            sdb     ONLINE       0     0     0
            sdc     ONLINE       0     0     0

errors: No known data errors

Get the ZFS version for tank’s pool:

# zpool get version tank
NAME  PROPERTY  VALUE    SOURCE
tank  version   -        default

Huh? I’m not sure why there’s no value set on ZFS running on Linux.

# zpool upgrade
This system supports ZFS pool feature flags.

All pools are formatted using feature flags.


Some supported features are not enabled on the following pools. Once a
feature is enabled the pool may become incompatible with software
that does not support the feature. See zpool-features(5) for details.

POOL  FEATURE
---------------
tank
      filesystem_limits
      large_blocks

Well, let’s upgrade the pool:

# zpool upgrade -a
This system supports ZFS pool feature flags.

Enabled the following features on 'tank':
  filesystem_limits
  large_blocks

It seems to have been successfully upgraded. Let’s verify:

# zpool status
  pool: tank
 state: ONLINE
  scan: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            sdb     ONLINE       0     0     0
            sdc     ONLINE       0     0     0

errors: No known data errors

# zpool get version tank
NAME  PROPERTY  VALUE    SOURCE
tank  version   -        default

Ref: http://freebsd.pro/topic/12/