Re: Advice sought on moving to AMD64
On Mon, Jun 20, 2005 at 11:46:36PM +0100, Rory Campbell-Lange wrote:
> We intend to use 2 SCSI disks in RAID1 for the system and the others in
> RAID10 for the DB.
>
> There is (obviously) a lot of debate about SATA vs SCSI on the
> Postgresql list. The general opinion is that 7200 rpm SATA disks just
> aren't fast/smart enough to cut it for serious database use, 10K Raptors
> being a possible exception. Since SCSI drives are designed "to do
> physical I/O scheduling, because the CPU can issue multiple commands
> before the drive has to report completion of the first one. IDE isn't
> designed to do that..." [Tom Lane], we're going for that.
IDE isn't but SATA is designed for that. The drives that are native
SATA appear to all support native command queueing. The new SATA
controllers are starting to support it too. The nforce4 does, but not
yet under linux. The AHCI(I think that's the arconym) SATA controllers
will support it too. I think it is only a 32 or so level command queue
rather than the 255 level supported by some scsi controllers and
devices, but much better than one command at a time.
Len Sorensen
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