pool: storage
 state: DEGRADED
status: One or more devices has experienced an unrecoverable error.  An
        attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
        using 'zpool clear' or replace the device with 'zpool replace'.
   see: http://zfsonlinux.org/msg/ZFS-8000-9P
  scan: scrub in progress since Wed Oct 18 17:55:08 2017
    272G scanned out of 665G at 512M/s, 0h13m to go
    8K repaired, 40.92% done
config:

        NAME                                      STATE     READ WRITE CKSUM
        storage                                   DEGRADED     0     0     0
          raidz2-0                                DEGRADED     0     0     0
            ata-Hitachi_HUA723020ALA641_YFH0ZXHA  ONLINE       0     0     0
            ata-Hitachi_HUA723020ALA641_YFH2808B  ONLINE       0     0     0
            ata-Hitachi_HUA723020ALA641_YGGLAUJA  ONLINE       0     0     0
            ata-Hitachi_HUA723020ALA641_YGGN6B7A  ONLINE       0     0     0
            sdf                                   OFFLINE      0     0     2  (repairing)

errors: No known data errors