Ubuntu – Replacing a dead disk in a zpool

13.04serverzfs

I'm running Ubuntu Server 13.04 64-bit using native ZFS. I have a zpool consisting of 4 hard drives of which one died yesterday and now is not being recognized by the OS or the BIOS anymore.

Unfortunately I saw the problem only after the next reboot so now the drive label is missing and I can't replace the disk using the official instructions here and here.

zpool status hermes -x

prints

root@zeus:~# zpool status hermes -x
  pool: hermes
 state: DEGRADED
status: One or more devices could not be used because the label is missing or
        invalid.  Sufficient replicas exist for the pool to continue
        functioning in a degraded state.
action: Replace the device using 'zpool replace'.
   see: http://zfsonlinux.org/msg/ZFS-8000-4J
  scan: scrub repaired 0 in 2h4m with 0 errors on Sun Jun  9 00:28:24 2013
config:

        NAME                         STATE     READ WRITE CKSUM
        hermes                       DEGRADED     0     0     0
          raidz1-0                   DEGRADED     0     0     0
            ata-ST3300620A_5QF0MJFP  ONLINE       0     0     0
            ata-ST3300831A_5NF0552X  UNAVAIL      0     0     0
            ata-ST3200822A_5LJ1CHMS  ONLINE       0     0     0
            ata-ST3200822A_3LJ0189C  ONLINE       0     0     0

errors: No known data errors

I already replaced the drive with a new one (which got the label /dev/disk/by-id/ata-ST3500320AS_9QM03ATQ)

Any one of the commands

zpool replace hermes /dev/disk/by-id/ata-ST3300831A_5NF0552X /dev/disk/by-id/ata-ST3500320AS_9QM03ATQ
zpool offline hermes /dev/disk/by-id/ata-ST3300831A_5NF0552X
zpool detatch hermes /dev/disk/by-id/ata-ST3300831A_5NF0552X

fails with

root@zeus:~# zpool offline hermes /dev/disk/by-id/ata-ST3300831A_5NF0552X
cannot offline /dev/disk/by-id/ata-ST3300831A_5NF0552X: no such device in pool

because the label of the drive that died does not exist in the system any more.I also tried the commands above omitting path to the drive's label to no avail.

How can I replace the "ghost" disk?

Best Answer

After digging endlessly this night I finally found the solution. The short answer is that you can use the disks' GUIDs (which persist even after disconnecting a drive) with the zpool command.

Long answer: I got the disk's GUID using the zdb command which gave me the following output

root@zeus:/dev# zdb
hermes:
    version: 28
    name: 'hermes'
    state: 0
    txg: 162804
    pool_guid: 14829240649900366534
    hostname: 'zeus'
    vdev_children: 1
    vdev_tree:
        type: 'root'
        id: 0
        guid: 14829240649900366534
        children[0]:
            type: 'raidz'
            id: 0
            guid: 5355850150368902284
            nparity: 1
            metaslab_array: 31
            metaslab_shift: 32
            ashift: 9
            asize: 791588896768
            is_log: 0
            create_txg: 4
            children[0]:
                type: 'disk'
                id: 0
                guid: 11426107064765252810
                path: '/dev/disk/by-id/ata-ST3300620A_5QF0MJFP-part2'
                phys_path: '/dev/gptid/73b31683-537f-11e2-bad7-50465d4eb8b0'
                whole_disk: 1
                create_txg: 4
            children[1]:
                type: 'disk'
                id: 1
                guid: 15935140517898495532
                path: '/dev/disk/by-id/ata-ST3300831A_5NF0552X-part2'
                phys_path: '/dev/gptid/746c949a-537f-11e2-bad7-50465d4eb8b0'
                whole_disk: 1
                create_txg: 4
            children[2]:
                type: 'disk'
                id: 2
                guid: 7183706725091321492
                path: '/dev/disk/by-id/ata-ST3200822A_5LJ1CHMS-part2'
                phys_path: '/dev/gptid/7541115a-537f-11e2-bad7-50465d4eb8b0'
                whole_disk: 1
                create_txg: 4
            children[3]:
                type: 'disk'
                id: 3
                guid: 17196042497722925662
                path: '/dev/disk/by-id/ata-ST3200822A_3LJ0189C-part2'
                phys_path: '/dev/gptid/760a94ee-537f-11e2-bad7-50465d4eb8b0'
                whole_disk: 1
                create_txg: 4
    features_for_read:

The GUID I was looking for is 15935140517898495532 which enabled me to do

root@zeus:/dev# zpool offline hermes 15935140517898495532
root@zeus:/dev# zpool status
  pool: hermes
 state: DEGRADED
status: One or more devices has been taken offline by the administrator.
        Sufficient replicas exist for the pool to continue functioning in a
        degraded state.
action: Online the device using 'zpool online' or replace the device with
        'zpool replace'.
  scan: scrub repaired 0 in 2h4m with 0 errors on Sun Jun  9 00:28:24 2013
config:

        NAME                         STATE     READ WRITE CKSUM
        hermes                       DEGRADED     0     0     0
          raidz1-0                   DEGRADED     0     0     0
            ata-ST3300620A_5QF0MJFP  ONLINE       0     0     0
            ata-ST3300831A_5NF0552X  OFFLINE      0     0     0
            ata-ST3200822A_5LJ1CHMS  ONLINE       0     0     0
            ata-ST3200822A_3LJ0189C  ONLINE       0     0     0

errors: No known data errors

and then

root@zeus:/dev# zpool replace hermes 15935140517898495532 /dev/disk/by-id/ata-ST3500320AS_9QM03ATQ
root@zeus:/dev# zpool status
  pool: hermes
 state: DEGRADED
status: One or more devices is currently being resilvered.  The pool will
        continue to function, possibly in a degraded state.
action: Wait for the resilver to complete.
  scan: resilver in progress since Sun Jun  9 01:44:36 2013
    408M scanned out of 419G at 20,4M/s, 5h50m to go
    101M resilvered, 0,10% done
config:

        NAME                            STATE     READ WRITE CKSUM
        hermes                          DEGRADED     0     0     0
          raidz1-0                      DEGRADED     0     0     0
            ata-ST3300620A_5QF0MJFP     ONLINE       0     0     0
            replacing-1                 OFFLINE      0     0     0
              ata-ST3300831A_5NF0552X   OFFLINE      0     0     0
              ata-ST3500320AS_9QM03ATQ  ONLINE       0     0     0  (resilvering)
            ata-ST3200822A_5LJ1CHMS     ONLINE       0     0     0
            ata-ST3200822A_3LJ0189C     ONLINE       0     0     0

errors: No known data errors

After resilvering had been completed everything worked well again. It would have been nice to include this information, that you can use a disk's GUID obtained through zdb with the zpool command, with the manpage of zpool.

Edit

As pointed out by durval below the zdb command may not output anything. Then you may try to use

zdb -l /dev/<name-of-device>

to explicitly list information about the device (even if it already is missing from the system).

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