Converting a non-HAST ZFS pool to a HAST pool

[Pawel Jakub Dawidek]

On Fri, Oct 15, 2010 at 11:37:34AM -0700, Freddie Cash wrote:
> Has anyone looked into, attempted, or considered converting a non-HAST
> ZFS pool configuration into a HAST one?  While the pool is live and
> the server is in use.  Would it even be possible?
> 
> For example, would the following work (in a pool with a single raidz2
> vdev, where the underlying GEOM provider is glabel)
>   - zpool offline 1 drive  (pool is now running degraded)
>   - configure hastd in master mode with a single provider using the
> "offline" disk (hast metadata takes the place of glabel metadata)

HAST metadata takes much more space than glabel metadata. The latter
takes only one sector, while the former depends on provider size, but we
have to keep entire extent bitmap there, so definitely more than one
sector.

>   - zpool replace the offline drive using the /dev/hast/whatever provider
>   - wait for ZFS to resilver the device
>   - repeat for each disk in the vdev
> 
> Is it possible to change the hast configuration and reload hastd to
> pick up new providers, without restarting it?  Without losing the
> /dev/hast devices?  Or would it require a restart, which would cause
> the /dev/hast/* devices to disappear, thus b0rking the pool?

It is possible in 8-STABLE.

> Just wondering how hard it's going to be to move from our current
> setup (backup server 1 rsync'd to backup server 2) to a HAST setup
> (server 1 hast master with server 2 hast slave).
> 
> If the above won't work, then I guess I'll have to grab a third
> storage box, configure that as a hast box, copy the data over, destroy
> server 2, configure it as a hast box, and let them sync.

I'm afraid you have to backup your pool, recreate it on HAST provider
and recover.

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