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

Stan Hoeppner stan at hardwarefreak.com
Wed Dec 15 17:09:11 EET 2010

Patrick Westenberg put forth on 12/15/2010 7:28 AM:
> Won't be 15k U320 SCSI disks also faster than average SATA disks for the
> indexes?

Yes.  A faster spindle speed allows for greater random IOPS.  Index file
reads/writes are random IOPS, and become more random with greater
concurrency, i.e. more users.

Although, I should point out that parallel SCSI (U320) is pretty much a
dead technology at this point.  AFAIK, no vendor has shipped a new
parallel SCSI disk line (only warranty replacements) for a number of
years now.  It has been superseded by Serial Attached SCSI (SAS).

I should also point out that the interface itself, whether parallel
SCSI, SAS, or SATA, makes little difference for random IOPS performance,
as long as the interface is running below the saturation point.  The
spindle speed and the drive firmware, specifically the queuing
implementation, are what make for a good transactional performance disk
drive.  Typically, 15k drives have the best transactional performance,
then 10k, then 7.2k, etc.


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