Re: Postgres on RAID5

All,

I have a 13 disk (250G each) software raid 5 set using 1 16 port adaptec SATA controller.
I am very happy with the performance. The reason I went with the 13 disk raid 5 set was for the space NOT performance.
  I have a single postgresql database that is over 2 TB with about 500 GB free on the disk.   This raid set performs
about the same as my ICP SCSI raid controller (also with raid 5).

That said, now that postgresql 8 has tablespaces, I would NOT create 1 single raid 5 set, but 3 smaller sets.  I also
DO
NOT have my wal and log's on this raid set, but on a  smaller 2 disk mirror.

Jim

---------- Original Message -----------
From: Greg Stark <gsstark@mit.edu>
To: Alex Turner <armtuk@gmail.com>
Cc: Greg Stark <gsstark@mit.edu>, Arshavir Grigorian <ag@m-cam.com>, linux-raid@vger.kernel.org,
pgsql-performance@postgresql.org
Sent: 14 Mar 2005 15:17:11 -0500
Subject: Re: [PERFORM] Postgres on RAID5

> Alex Turner <armtuk@gmail.com> writes:
>
> > a 14 drive stripe will max out the PCI bus long before anything else,
>
> Hopefully anyone with a 14 drive stripe is using some combination of 64 bit
> PCI-X cards running at 66Mhz...
>
> > the only reason for a stripe this size is to get a total accessible
> > size up.
>
> Well, many drives also cuts average latency. So even if you have no need for
> more bandwidth you still benefit from a lower average response time by adding
> more drives.
>
> --
> greg
>
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