zdb

eirac@dazzler:~$ sudo zpool status
  pool: rpool
 state: ONLINE
  scan: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        rpool       ONLINE       0     0     0
          c4t0d0    ONLINE       0     0     0

errors: No known data errors
neirac@dazzler:~$ sudo zdb -C rpool | grep ashift
zdb: can't open 'rpool': No such device or address
neirac@dazzler:~$