[Dovecot] Question about "slow" storage but fast cpus, plenty of ram and dovecot

[Brad Davidson]

On Dec 12, 2010, at 23:26, Javier de Miguel Rodrí guez <javierdemiguel at us.es> wrote:

> 
>    My SAN(s) (HP LeftHand Networks) do not support SSD, though. But I have several LeftHand nodes, some of them with raid5, others with raid 1+0. Maildirs+indexes are now in raid5, maybe I can separate the indexes to raid 1+0 iscsi target in a different san
> 
>    I have two raid5 (7 disks+1 spare) and I have joined them via LVM stripping. Each disk is SAS 15k rpm 450GB, and the SANs have 512 MB-battery-backed-cache. In our real workload (imapsync), each raid5 gives around 1700-1800 IOPS, combined 3.500 IOPS.

Your 'slow' storage is running against 16 15k RPM SAS drives? Those LeftHand controllers must be terrible. We have Maildir on NFS on a Netapp with 15k RPM 450GB FC disks and have never had performance problems, even when running the controllers up against the wall by mounting with the noac option (60k NFS IOPS!). We were using 500GB 4500 RPM ATA disks at that point - doesn't get much slower than that.

Our current environment actually houses POP/IMAP/SMTP/web for 60k accounts, and an ESX cluster (12k NFS IOPS) without breaking a sweat. We'll soon be adding 128 1TB disks to the same controllers for Exchange, and should still have capacity to spare.

Not particularly helpful to your situation I know, but next time you are looking at storage you might reevaluate your current strategy.

-Brad