Musings on ZFS Backup strategies

Karl Denninger karl at
Fri Mar 1 20:37:34 UTC 2013

On 3/1/2013 2:34 PM, Daniel Eischen wrote:
> On Fri, 1 Mar 2013, Ben Morrow wrote:
>> Quoth Daniel Eischen <deischen at>:
>>> Yes, we still use a couple of DLT autoloaders and have nightly
>>> incrementals and weekly fulls.  This is the problem I have with
>>> converting to ZFS.  Our typical recovery is when a user says
>>> they need a directory or set of files from a week or two ago.
>>> Using dump from tape, I can easily extract *just* the necessary
>>> files.  I don't need a second system to restore to, so that
>>> I can then extract the file.
>> As Karl said originally, you can do that with snapshots without having
>> to go to your backups at all. With the right arrangements (symlinks to
>> the .zfs/snapshot/* directories, or just setting the snapdir property to
>> 'visible') you can make it so users can do this sort of restore
>> themselves without having to go through you.
> It wasn't clear that snapshots were traversable as a normal
> directory structure.  I was thinking it was just a blob
> that you had to roll back to in order to get anything out
> of it.
> Under our current scheme, we would remove snapshots
> after the next (weekly) full zfs send (nee dump), so
> it wouldn't help unless we kept snapshots around a
> lot longer.
> Am I correct in assuming that one could:
>   # zfs send -R snapshot | dd obs=10240 of=/dev/rst0
> to archive it to tape instead of another [system:]drive?

-- Karl Denninger
/The Market Ticker ®/ <>
Cuda Systems LLC

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