Re: [Dovecot] Howto add another disk storage

[Wojciech Puchar]

is random seek latency.  And the faster the spindle, the lower the
latency.  Thus 15k Seagate SAS drives are excellent candidates for mail
store duty, as are any 10k or 15k drives.
definitely not counting by $/IOPS rate. even worse looking with $/GB which 
is more important unless you make <1GB mail account.