ZFS unable to import pool

Tom Evans tevans.uk at googlemail.com
Wed Apr 23 16:20:59 UTC 2014

On Wed, Apr 23, 2014 at 4:10 PM, Karl Denninger <karl at denninger.net> wrote:
> I have a large home system as well.
> But I do back it up to other spinning pieces of rust, and rotate the backups
> out to a bank safe-deposit box.  If I make a terrible mistake (or my
> hardware and/or software does) I have a means of recovery.  There are no
> guarantees of course in that I COULD wind up with a bad disk in the safe
> deposit box, but if my house burns down I have a shot at recovery with high
> odds of success -- an act that would otherwise be impossible.  Partitioning
> my data off into "essentially archival, read-almost-only" and "active" means
> that the former needs to be updated rarely and the former is of small enough
> size that I don't go crazy doing it either in money or time.

I recently re-jigged my setup to do just this - the root pool and
working set are on a pair of SSDs, and the rarely written and seldom
read data lives on a special archive pool - 8 disk raidz2.

> And I *HAVE* had things like this happen -- twice in the last 20 years I've
> had a disk adapter go insane and scribble on MULTIPLE spindles at once.
> There is no RAID strategy that will protect you against this event; you
> either have a backup or you're done.

I didn't want to know that :)

> ZFS actually makes this easier with send/receive and the ability to import a
> pool, send to it and then export it.  The backup pool can have compression
> turned on where for performance reasons it may not make sense for the online
> pool to do so.  And you can rotate that out fairly easily too; you can take
> a 2-way mirror, add a third disk and let it resilver, then split the third
> one off and remove it, giving you a dismounted copy you can then stick in a
> box and yet if you need it -- it's there.

I should be doing more of this, although it is trickier to do with a
large pool. Splitting my datasets in to smaller chunks would help to
backup to dismounted pools.

Interesting advice, thanks Karl!



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