Backup strategy for large mailbox stores

Eric Luyten Eric.Luyten at
Fri Feb 19 10:50:37 EST 2010

On Tue, February 16, 2010 9:49 am, Eric Luyten wrote:
> ZFS is awesome.
> We have a ZFS pool composed of nine LUNs on an iSCSI-connected (2 x 1 Gbps)
> EMC Celerra. All disks are 7200 rpm S-ATA.
> On our previous storage system (FC-AL connected StorageTek with 15k and 10k
> rpm FC disks) I was able to run more finds/dumps/... in parallel without
> impacting mail service performance or message delivery rate.
> Even now I can pull close to 100 MB/s from the mail section of the storage
> subsystem without users noticing.   48 GB RAM on the mailserver sure helps,
> plenty of ARC :-)

(thought I'd share this with you lot :-)

Yesterday morning our mail server suffered a severe slowdown, leading to
hundreds of IMAP and POP clients hitting various timeouts, users getting
upset and starting to call helpdesks (offices down my hallway).

All filesystems appeared sluggish at Solaris level while the iSCSI network
links and the SAN were only moderately loaded. Weird.

Luckily I had recently read (on info-cyrus ? cannot find the article right
now) about a "ZFS > 80%" condition.

Our Z pool was 83% full ...
Deleted the December snapshots, which brought that figure down to 74%

Performance came right back  :-)

Eric (whew)

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