ZFS backup advice

Ulrich Spoerlein uspoerlein at gmail.com
Thu Dec 11 09:53:54 PST 2008


I'm looking for advice on setting up a ZFS based hard disk backup
solution. Given a large set of data, with perhaps 500MB data changes per
day and two 1 TB disks, which option would you prefer and why:

A) Separate ZFS pools on both disk. Using zfs send|recv to transfer
snapshots every 2-3 days, taking the "backup" pool offline in the time
in between (to keep the disk safe from surges, etc).


B) One ZFS mirror pool across both disk, resilvering the second half
every 2-3 days and then detaching it again.

Right now I'm favouring option A, as I can selectively "backup" part of
the pool (excluding /usr/obj for example, though it is <10% of total
capacity, so not a strong point), can use compression on the backup-pool
and can potentially keep more snapshots on it than on the live pool.
It should also be faster than resilvering the mirror every other day.

I'd use B, iff ZFS is able to "self-heal" defective sectors on one
mirror half, even if it is not fully resilvered. Does anyone know if
this is possible?

Please keep me CC'ed. Thanks!

Ulrich Spoerlein
It is better to remain silent and be thought a fool,
than to speak, and remove all doubt.

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