Backup strategy for large mailbox stores

Vincent Fox vbfox at
Tue Feb 16 13:45:46 EST 2010

Andrew Morgan wrote:
> Is there really a significant downside to performing backups on a hot 
> cyrus mailstore?  Should I care if Suzie's INBOX was backed up at 3am 
> and Sally's INBOX was backed up at 4am?
> Vincent, on a slightly related note, what is your server and SAN 
> hardware?
I dunno, perhaps the Cyrus gurus could answer that better.
I rather assumed I would want my meta information to match
fairly closely the contents of the inboxes at that point in time.
My belief was that if I had to a full restore after a disaster
that I would have to spend substantial time doing reconstruct
in order to get the databases to represent actual state.
Thus having a point-in-time snapshot would be better for DR.
Perhaps I'm wrong about that.

Servers are fairly modest mostly Sun V245 a couple of T2000.
Storage is a Belt and suspenders sort of hybrid/layered approach.
We use a pair of cheapish Sun 2540 arrays.  We multipath
them through SAN switches.  The arrays are configured
with 2  5-disk RAID-5 LUNs and 2 hot spares.  Then from
the server view the 4 LUNS visible are pooled into a
simple ZFS RAID-10.   Since the mirror parts are composed
of LUNS from each array, an entire array can go offline and
it's mirror copy in the other array ensures uptime.  I have
had an entire array go down once due to controller issues
and hey who HASN'T had an operator or someone working on
cables pull the wrong power cords?  It happens.

We'd have to have 2 disk fail in a RAID-5 LUN and another
disk in another LUN before I even furrow my brow.  I've
seen enough double-disk failures in RAID sets for one
lifetime and certainly don't want to see one on mail store.
Storage is cheap, downtime is not.  Ordinary single-disk
failures are handled through the array firmware swapping
in a hot spare and barely rate notice except we have to
eventually replace the dead disk.

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