zpool import by UUID?

[David Abrahams]

Hi,

I made the mistake of creating a pool of disks using letter names
(e.g. /dev/sda, /dev/sdb...), and then I plugged in an external disk
before boot. Of course it conveniently occupied /dev/sda and shifted
all my zfs disks over, so alright, I did a zpool export and a zpool import
and everything was recovered. Great, except I wish I'd created the pool
using devices named in /dev/disk/by-uuid instead. So I tried

zpool export olympic
zpool import -d /dev/disk/by-uuid olympic

and... nothing. Also,

zpool import -d /dev/disk/by-uuid

still nothing. Is there any way to get this pool to use the UUID names,
or do I have to start over from scratch?

Thanks,

--
Dave Abrahams
BoostPro Computing
http://www.boostpro.com

[drewpca]

> and everything was recovered.  Great, except I wish I'd created the pool
> using devices named in /dev/disk/by-uuid instead.  So I tried
>
>   zpool export olympic
>   zpool import -d /dev/disk/by-uuid olympic
>

Alas, zfs-fuse turns alternate names back into the 'sda' device names
after your first export/import. I was trying to use /dev/disk/by-id
instead of by-uuid, but I imagine you'll see the same thing.

On the bright side, I haven't had any issues with device names
shifting around. ZFS seems to always figure out which disks belong in
which pool positions. I just have to do some extra dereferencing of
'sda' names when I'm debugging things.



Incidentally, I made the mistake of using sdf1 as the first disk in a
mirror my first time.

# zpool attach stor2 sdf1 /dev/disk/by-id/ata-Maxtor_7H500F0_H81E75AH
cannot attach /dev/disk/by-id/ata-Maxtor_7H500F0_H81E75AH to sdf1: no
such device in pool

I eventually migrated everything to a whole disk (sdg instead of sdg1)
and then rebuilt the mirror with 'sdf'. For the migration I had to use
rsync, since send/receive would stall and require a zfs restart. Maybe
this is because zfs-fuse doesn't support two zfs commands running at
once (aka "zfs send x | zfs receive y")? Anyway, the snapshots that I
lost were not important, and now things have been smooth for 10+ days.

[Ricardo M. Correia]

Hi David,

On Qui, 2008-09-25 at 14:32 -0400, David Abrahams wrote:
>
> Hi,
>
> I made the mistake of creating a pool of disks using letter names
> (e.g. /dev/sda, /dev/sdb...), and then I plugged in an external disk
> before boot. Of course it conveniently occupied /dev/sda and shifted
> all my zfs disks over, so alright, I did a zpool export and a zpool import
> and everything was recovered. Great, except I wish I'd created the pool
> using devices named in /dev/disk/by-uuid instead.

Why would you want to use /dev/disk/by-uuid as opposed
to /dev/disk/by-id?

> So I tried
>
> zpool export olympic
> zpool import -d /dev/disk/by-uuid olympic
>
> and... nothing. Also,
>
> zpool import -d /dev/disk/by-uuid
>
> still nothing. Is there any way to get this pool to use the UUID names,
> or do I have to start over from scratch?

Currently, there isn't, because ZFS devices are not put
into /dev/disk/by-uuid.

I think (but I'm not sure) that libvolume_id in udev is responsible for
extracting the UUIDs that go into /dev/disk/by-uuid, but obviously it
doesn't know about ZFS yet.

Perhaps using "zpool import -d /dev/disk/by-id" would do what you want?

Cheers,
Ricardo

[Ricardo M. Correia]

On Qui, 2008-09-25 at 12:33 -0700, drewpca wrote:
> Alas, zfs-fuse turns alternate names back into the 'sda' device names
> after your first export/import.

That's because by default zfs-fuse only searches for disks in /dev (it
doesn't go into subdirectories).

The reason for this default is that /dev/disk/by-id is not available
everywhere, although I guess I could implement some kind of
autodetection.

If you want to get your alternate names back, you can use "zpool import
-d /dev/disk/by-id".

> I was trying to use /dev/disk/by-id
> instead of by-uuid, but I imagine you'll see the same thing.
>
> On the bright side, I haven't had any issues with device names
> shifting around. ZFS seems to always figure out which disks belong in
> which pool positions. I just have to do some extra dereferencing of
> 'sda' names when I'm debugging things.

Good to hear :)

Cheers,
Ricardo

[Rudd-O]

Oh yeah, I also discovered by accident that you can't run zfs send and
zfs receive in the same machine. It stalls because only one zfs
command may be running at any point.

[Chris Samuel]

That's odd, it certainly used to work as I used it to move data between
different ZFS pools on this machine..

--
Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC

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