Re: [PERFORM] Quad processor options

On 12 May 2004, at 12:17 PM, Manfred Koizar wrote:

> On Tue, 11 May 2004 15:46:25 -0700, Paul Tuckfield <paul(at)tuckfield(dot)com>
> wrote:
>
>> - I'll bet you have a low value for shared buffers, like 10000. On
>> your 3G system
>> you should ramp up the value to at least 1G (125000 8k buffers)
>
> In most cases this is almost the worst thing you can do. The only
> thing
> even worse would be setting it to 1.5 G.
>
> Postgres is just happy with a moderate shared_buffers setting. We
> usually recommend something like 10000. You could try 20000, but don't
> increase it beyond that without strong evidence that it helps in your
> particular case.
>
> This has been discussed several times here, on -hackers and on
> -general.
> Search the archives for more information.

We have definitely found this to be true here. We have some fairly
complex queries running on a rather underpowered box (beautiful but
steam-driven old Silicon Graphics Challenge DM). We ended up using a
very slight increase to shared buffers, but gaining ENORMOUSLY through
proper optimisation of queries, appropriate indices and the use of
optimizer-bludgeons like "SET ENABLE_SEQSCAN = OFF"

Hal