Your RAID is failing you (Re: [zfs-discuss] Re: Question regarding resizeing/expanding a zpool)

Gregor Kopka gregor at kopka.net
Sun Apr 15 05:53:43 EDT 2012


Hi peram,

Am 15.04.2012 01:26, schrieb peram:
> The status of the spool is this :
>
> peram at ubuntu:/$ sudo zpool status NAS
>    pool: NAS
>   state: ONLINE
> status: One or more devices has experienced an error resulting in data
> 	corruption.  Applications may be affected.
> action: Restore the file in question if possible.  Otherwise restore
> the
> 	entire pool from backup.
>     see: http://zfsonlinux.org/msg/ZFS-8000-8A
>   scan: scrub repaired 5.50K in 9h58m with 1 errors on Sat Apr 14
> 04:54:42 2012
> config:
>
> 	NAME        STATE     READ WRITE CKSUM
> 	NAS         ONLINE       0     0     1
> 	  sdc1      ONLINE       0     0     3
>
> errors: 1 data errors, use '-v' for a list

As you can see from this zpool status: *your RAID has failed, some of 
your data is lost.
*
Caused by your setup ZFS sees only one device, hence it's self-healing 
capacities are severely crippled.
And you already have been bitten by it:

The RAID happily returned 3 blocks of garbage, for two of them ZFS was 
able to correct the damage delivered by the underlying storage system 
(must have been metadata which is always redundant in ZFS). But the 
contents of one data block hadn't had redundancy in ZFS, thus couldn't 
be repaired and _is lost_ (use 'zpool status NAS -v' to see what 
file/zvol was damaged).

Do yourself a favour and let ZFS handle redundancy, your RAID clearly 
isn't able to do it.

Todo:

  * backup the complete pool (zfs send/recv can do the trick nicely
  * break up the RAID into JBOD
  * expose the individual disks (using /dev/disk/by-id paths)
  * build a new pool on them with mirrors or raidz for redundancy

> I've tried to export and then import the pool again, but the allocated
> size remains the same.
>
> So to sum it up, my disk device is bigger than what I have available
> in my zpool.  What have I forgotten to do ?
zpool offline -t /dev/sdc1    # take disk offline
zpool online -e /dev/sdc1    # online it and expand

Better plan still is to do youself the favour as above.

Regards,

  Gregor
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