Re: inferior SCSI performance

On Wed, Oct 01, 2003 at 07:14:32AM -0600, scott.marlowe wrote:
> FYI, on a Dual PIV2800 with 2 gig ram and a single UDMA 80 gig hard drive,
> I from 420 tps to 22 tps when I disable write caching. WOW. A factor of
> about 20 times slower. (pgbench -c 4 -t 100)

That's completely consistent with tests Chris Browne has done here on
cache-enabled and cache-disabled boxes that we have.

It's a _really_ big difference. The combination of battery-backed
write cache on your controller plus a real good UPS is quite possibly
the number one thing you can do to improve performance. For what
it's worth, I can't see how this is something special about Postgres:
even raw-filesystem type systems have to make sure the disk actually
has the data, and a write cache is bound to be a big help for that.

A

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