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Have been running a test instance of a NAS using a ZFS as mentioned in Restoring an Ubuntu Server using ZFS RAIDZ for data.

This week one of my disks died. Shouldn't be a problem, should it (the benefits of RAID being resilience as well as performance)?

Except that my ZFS pool got corrupted, as in:

andy@ubuntu:~$ sudo zpool status -v
  pool: tank
 state: UNAVAIL
status: One or more devices could not be used because the label is missing
        or invalid.  There are insufficient replicas for the pool to continue
        functioning.
action: Destroy and re-create the pool from
        a backup source.
   see: http://www.sun.com/msg/ZFS-8000-5E
  scan: none requested
config:

    NAME        STATE     READ WRITE CKSUM
    tank        UNAVAIL      0     0     0  insufficient replicas
      raidz1-0  UNAVAIL      0     0     0  insufficient replicas
        sdb     FAULTED      0     0     0  corrupted data
        sdc     FAULTED      0     0     0  corrupted data
        sdd     UNAVAIL      0     0     0

Fortunately this is a test instance and so I can easily start again. But what if this pool contained important data? What would the right next step(s) be to recover the data and restore my NAS to working order? Or does ZFS automatically try all possible restoration approaches, such that the data is now toast?

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4 Answers

up vote 1 down vote accepted

It looks like your pool may not actually be corrupted. Though from the output it seems like multiple devices may be in trouble. I am guessing multiple disks may be in questionable state, hence the faulted state on sdb and sdc. Figure out what might be wrong with them and your pool may prove you wrong. This does not look like a fatal state of pool.

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Thanks slashdot. How do I go about figuring out what might be wrong with them? Scrub doesn't seem to work on an offline disk. I'll try again given renewed energy by your reply. –  andybjackson Feb 3 '12 at 19:59
    
Slashdot's answer hints but does not give the solution, which is to export the pool and reimport, preferably after having replaced the dead drive. –  andybjackson Feb 8 '12 at 16:42
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Armed with the insight of @slashdot, I have mostly fixed my problem, but I don't really know what I did. Please examine the following trail and enlighten me.

In particular which of the following hypotheses are true and or what am I missing?

  1. Neither zdb -u tank nor zdb -dcsv tank did anything useful.
  2. The second zpool import -f tank worked when the first one didn't because enough time had elapsed since the zpool export tank for ZFS to have a chance to fix itself.
  3. This whole episode had something to do with labels changing themselves after one of the drives failed (think it was sdb which caused sdc>sdb & sdd>sdb).

LOG

andy@ubuntu:~$ zpool status
andy@ubuntu:~$ sudo zpool status
  pool: tank
 state: UNAVAIL
status: One or more devices could not be used because the label is missing
        or invalid.  There are insufficient replicas for the pool to continue
        functioning.
action: Destroy and re-create the pool from
        a backup source.
   see: http://www.sun.com/msg/ZFS-8000-5E
  scan: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        UNAVAIL      0     0     0  insufficient replicas
          raidz1-0  UNAVAIL      0     0     0  insufficient replicas
            sdb     FAULTED      0     0     0  corrupted data
            sdc     FAULTED      0     0     0  corrupted data
            sdd     UNAVAIL      0     0     0
andy@ubuntu:~$ sudo zdb -u tank
zdb: can't open 'tank': No such device or address
andy@ubuntu:~$ sudo zpool scrub tank
cannot scrub 'tank': pool is currently unavailable
andy@ubuntu:~$ sudo zdb -bcsv tank
zdb: can't open 'tank': No such device or address
andy@ubuntu:~$ sudo zpool export tank
andy@ubuntu:~$ sudo zpool import tank
cannot import 'tank': pool may be in use from other system
use '-f' to import anyway
andy@ubuntu:~$ sudo zpool import -f tank
cannot import 'tank': one or more devices is currently unavailable
andy@ubuntu:~$ sudo zpool status
no pools available
andy@ubuntu:~$ sudo zpool status -x
no pools available
andy@ubuntu:~$ sudo zpool import
  pool: tank
    id: 9117894036185671023
 state: UNAVAIL
status: One or more devices contains corrupted data.
action: The pool cannot be imported due to damaged devices or data.
   see: http://www.sun.com/msg/ZFS-8000-5E
config:

        tank        UNAVAIL  insufficient replicas
          raidz1-0  UNAVAIL  insufficient replicas
            sdb     FAULTED  corrupted data
            sdb     UNAVAIL
            sdc     ONLINE
andy@ubuntu:~$ sudo zpool import tank
cannot import 'tank': pool may be in use from other system
use '-f' to import anyway
andy@ubuntu:~$ sudo zpool import -f tank
andy@ubuntu:~$ sudo zpool status
      pool: tank
 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://www.sun.com/msg/ZFS-8000-4J
  scan: scrub repaired 0 in 0h13m with 0 errors on Mon Nov 21 09:22:11 2011
config:

        NAME                      STATE     READ WRITE CKSUM
        tank                      DEGRADED     0     0     0
          raidz1-0                DEGRADED     0     0     0
            10820373921989571629  UNAVAIL      0     0     0  was /dev/sdb1
            sdb                   ONLINE       0     0     0
            sdc                   ONLINE       0     0     0

errors: No known data errors
andy@ubuntu:~$
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I'm going to go with (3). –  tomfanning Mar 26 '13 at 8:41
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Can you just mixed up disks?

Once I mixed up disks and zpool said "disks contain corrupted data". After I connected disks in previous sequence it started working.

Maybe after you imported tank zpool recognized right sequence.

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BBK I think you are correct - that the change of sequence initiated the problem. Why did the first import then not work? Ashamed to say that I have scuttled back to XFS. –  andybjackson Feb 11 '12 at 23:15
    
If you find my answer correct, please aprove it. Give zfs a chance. It is very nice FS. May be system released hdd from zpool, only after that you was able to import it, sort of. –  BBK Feb 13 '12 at 18:07
    
BBK I have upvoted your answer, but am afraid that I think @slashdot's answer is more generically helpful. Also, I'm not sure what the first sentence "Can you just mixed up disks?" means - may help to clarify. I think we got to the bottom of what went wrong, even if we didn't articulate it that well, but haven't dealt that well with fix advice yet. –  andybjackson Feb 15 '12 at 8:06
    
In case you are using SATA disks: It might be that previously you had next situation: sdb was connected to SATA2, sdc was connected to SATA3, sdd was connected to SATA4. And after your sdd had faulted, perhaps you mixed up the rest of the disks: sdb to SATA3, sdd to SATA2 or something like that. –  BBK Feb 19 '12 at 21:05
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I think the previous posters have highlighted the problem. The probable cause was due to the way you specified the disks.

My experience is with ZFS on Ubuntu. Though I do use ZFS on freenas as well, I've never had to delve into the bsd implementation.

Certainly for Ubuntu, you are strongly advised to specify your devices by-id rather than by descriptor: i.e. /dev/disk/by-id/scsi-SATA-long string that uniquely ids the physical disk rather than /dev/sda.

Using by-id device removes any dependence on the specific SATA port the disk is connected to.

Gareth

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