ZFS and disk naming change (ex. da0->da4)

[Pawel Jakub Dawidek]

On Wed, Oct 24, 2007 at 04:48:38PM +0200, Attila Nagy wrote:
> Hello,
> 
> I have an experimental (but that does not mean, I wouldn't like to get 
> my data back :) zpool, which was created with something like this:
> zpool create people raidz2 /dev/da0 /dev/da3 /dev/da4, etc
> 
> The problem is those device names have been changed during the next 
> reboot (the cause of this is irrelevant, but mainly because some of them 
> were not attached at the original boot, just later, so at the next 
> reboot the disks came up in a different order), so now I have:
> zpool status
>  pool: people
> state: UNAVAIL
> status: One or more devices could not be opened.  There are insufficient
>        replicas for the pool to continue functioning.
> action: Attach the missing device and online it using 'zpool online'.
>   see: http://www.sun.com/msg/ZFS-8000-D3
> scrub: none requested
> config:
> 
>        NAME        STATE     READ WRITE CKSUM
>        people      UNAVAIL      0     0     0  insufficient replicas
>          raidz2    UNAVAIL      0     0     0  insufficient replicas
>            da0     UNAVAIL      0     0     0  cannot open
>            da3     ONLINE       0     0     0
>            da4     FAULTED      0     0     0  corrupted data
>            da5     FAULTED      0     0     0  corrupted data
>            da6     FAULTED      0     0     0  corrupted data
>            da7     FAULTED      0     0     0  corrupted data
>            da8     FAULTED      0     0     0  corrupted data
>            da9     FAULTED      0     0     0  corrupted data
> 
> (it seems da3 is still da3 :)
> 
> My question is: what now? Is it possible to regain the pool, or is it 
> totally busted now? I am not sure that I can figure out which device is 
> which now...
> 
> I've only played with ZFS on Solaris with FC targets, and there I've 
> never faced this problem, because of the static naming.

ZFS caches components names in /boot/zfs/zpool.cache. You may remove
this file and import the pool again.

ZFS can handle name changes, but currently only with ATA disks. It can
find disk using it's ID. I've a patch for SCSI disks, but it's probably
not entirely correct:

	http://people.freebsd.org/~pjd/patches/scsi_da_ident.patch

We need some SCSI guru to implement it properly.

> ps: I guess next time I will use glabel -I love that- to provide base 
> devices...

Yes, glabel seems like a good work-around for now. In some cases we will
never be able to provide disk's ID, eg. for USB pen-drives, etc.

-- 
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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