$sudo zpool upgrade zdb_pool
This system is currently running ZFS pool version 28.

Successfully upgraded 'zdb_pool' from version 22 to version 28

$ zpool get version zdb_pool
NAME      PROPERTY  VALUE    SOURCE
zdb_pool  version   28       default

$ zdb -C zdb_pool

MOS Configuration:
        version: 22
        name: 'zdb_pool'
        state: 0