ZFS for Cyrus IMAP storage
Rudy.Gevaert at UGent.be
Sat May 5 17:20:32 EDT 2007
Vincent Fox wrote:
> I originally brought up the ZFS question.
> We seem to have arrived at a similar solution after much
> experimentation. Meaning using ZFS for the things it does well already,
> and leveraging proven hardware to fill in the weak spots.
> I have a pair of Sun 3510FC arrays we have exported 2 RAID5 LUNs (5
> disks each) with one on primary and the other on second controller. This
> is to exploit the active-active controller feature of the 3510FC. We
> are also doing multipathing through a pair of SAN fabric switches.
> On top of that we then use ZFS to join a LUN from each array into a
> mirror pair, and then add the other pair as well. I guess you could call
> it RAID 5+1+0. This architecture allows us to add more storage to the
> pool while online, by adding more 3510FC array pairs to the pool.
> Performance in benchmarking (Bonnie++ etc.) has shown to be little
> different from turning them into JBOD and doing everything with ZFS.
> Behavior is more predictable to me since I know that the 3510 firmware
> knows how to rebuild a RAID5 set using the assigned spare drive in that
> array. With ZFS I see no way to specify which disk is assigned as spare
> to a particular set of disks, which could mean a spare is pulled from
> another array.
> It's pretty nifty to be able to walk into the machine room and flip off
> the power to an entire array and things keep working without a blip.
> It's not the most efficient usage of disk space but with performance &
> safety this promising for an EMAIL SERVER it will definitely be
> welcome. I dread the idea of silent data corruption or long fsck time
> on a 1+ TB mail spool which ZFS should save us from. I have atime=off
> and compression=on. Our setup is slightly different from yours in that
> we are clustering 2 T2000 with 8GB RAM each, and we are currently
> setting up Solaris Cluster 3.2 software in failover configuration so we
> can patch without downtime.
> Thanks for the idea about daily snapshots for recovering recent data, I
> like that idea a lot. I'll tinker around with it I wonder if there'd be
> much penalty to upping the snapshots to every 8 hours. Depends on how
> much churn there is in your mail spool I suppose.
> This system should move into production later this month. We have
> 70,000 accounts that we'll begin a long and slow migration from our
> UW-IMAP pool of servers. We have an existing Perdition proxy server
> setup, which will allow us to migrate users transparently. Hopefully
> I'll have more good things to say about it sometime thereafter.
Are you going to do this with "1" perdition server? Make sure you have
compiled perdition with /dev/urandom, or an other sort of non blocking
entropy providing device :)
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