Re: What's the best hardver for PostgreSQL 8.1?

Bruce,

On 12/27/05 9:51 AM, "Bruce Momjian" <pgman(at)candle(dot)pha(dot)pa(dot)us> wrote:

> Historically, I have heard that RAID5 is only faster than RAID10 if
> there are six or more drives.

I think the real question here is "faster for what?" Also, just like the
optimizer tunables for cpu/disk/memory speed relationships, the standing
guidance for RAID has become outdated. Couple that with the predominance of
really bad hardware RAID controllers and people not testing them or
reporting their performance (HP, Adaptec, LSI, Dell) and we've got a mess.

All we can really do is report success with various point solutions.

RAID5 and RAID50 work fine for our customers who do OLAP type applications
which are read-mostly. However, it only works well on good hardware and
software, which at this time include the HW RAID controllers from 3Ware and
reputedly Areca and SW using Linux SW RAID.

I've heard that the external storage RAID controllers from EMC work well,
and I'd suspect there are others, but none of the host-based SCSI HW RAID
controllers I've tested work well on Linux. I say Linux, because I'm pretty
sure that the HP smartarray controllers work well on Windows, but the Linux
driver is so bad I'd say it doesn't work at all.

WRT RAID10, it seems like throwing double the number of disks at the
problems is something to be avoided if possible, though the random write
performance may be important for OLTP. I think this assertion should be
retested however in light of the increased speed of checksumming hardware
and / or CPUs and faster, more effective drive electronics (write combining,
write cache, etc).

- Luke