2012-10-05 13:13, Tiernan OToole wrote:
Thanks for that Jim!

Sounds like a plan there... One question about the storing ZFS dumps in
a file... So, the idea of storing the data in a SFTP server which has an
unknown underlying file system... Is that defiantly off limits, or can
it be done?

Mileages do vary. Maybe you should pack the stream files into
archives with error-correction codes (or at least verification
CRCs) like ZIP, RAR, likely p7zip, maybe others; and also keep
checksum files. At least this can help detect or even fix small
nasty surprises.

The general concern is that zfs send streams have no built-in
redundancy, I'm not sure about error-checking - likely it is
there. And it is widely assumed that this being a stream, a small
error can redirect the flow widely differently from expectations
and cause the whole dataset state to be invalid (likely this
snapshot receiving will be aborted, and then you can't receive
any newer ones over it).

That said, some people do keep the streams on tape; the NDMP
tools and protocol from Sun IIRC do the same for backups.
So it's not off-limits, but precautions may be due (keep 2+
copies, do CRC/ECC and so on).

> and should i be doing a full dump or just an incremental
> one? maybe incremental daily, and then a full dump weekly?

A full dump of a large filesystem can be unbearably large for
storage and transfers. Still, the idea of storing occasional
full snapshots and a full history of incrementals (so that you
can try to recover starting from any of the full snapshots you
have) sounds sane. This way you have a sort of second copy by
virtue of a full snapshot incorporating some state of the dataset
and if the most recent one is broken - you can try to recover
with the one(s) before it and applying more incremental snapshots.
Likewise, errors in very old snapshots become irrelevant when a
newer full snapshot is intact. But sometimes two or more things
can break - or be detected to break - at once ;)

In particular, regular drills should be done (and provisioned
for) to test that you can in fact recover from your backups,
and that they do contain all the data you need. Older configs
can become obsolete as live systems evolve...


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