Re: Adding RAM: seeking advice & warnings of hidden "gotchas"

If you have 3 1.5GB tables then you might as well go for 4GB while you're at
it.  Make sure you've got a bigmem kernel either running or available, and
boost effective_cache_size by whatever amount you increase the RAM by.  We
run a Quad Xeon/4GB server on Redhat 7.3 and it's solid as a rock.

There is no way I know of to get indexes preferentially cached over data
though.

Matt

> -----Original Message-----
> From: pgsql-performance-owner@postgresql.org
> [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of Nick
> Fankhauser
> Sent: 17 December 2003 19:57
> To: Pgsql-Performance@Postgresql. Org
> Subject: [PERFORM] Adding RAM: seeking advice & warnings of hidden
> "gotchas"
>
>
> Hi-
>
> After having done my best to squeeze better performance out of our
> application by tuning within our existing resources, I'm falling back on
> adding memory as a short-term solution while we get creative for
> a long-term
> fix. I'm curious about what experiences others have had with the
> process of
> adding big chunks of RAM. In particular, if I'm trying to encourage the OS
> to cache more of my index information in RAM, what sort of configuration
> should I do at both the PostgreSQL and OS level?
>
> In a slightly off-topic vein, I'd also like to hear about it if
> anyone knows
> about any gotchas at the OS level that might become a problem.
>
> The server is a dual processor Athlon 1.2GHz box with hardware
> SCSI RAID. It
> currently has 1 GB RAM, and we're planning to add one GB more for
> a total of
> 2GB. The OS is Debian Linux Kernel 2.4.x, and we're on PostgreSQL v7.3.2
>
> My current memory related settings are:
>
> SHMMAX and SHMALL set to 128MB (OS setting)
> shared buffers 8192 (64MB)
> sort_mem 16384 (16MB)
> effective_cache_size  65536 (512MB)
>
>
> We support up to 70 active users, sharing a connection pool of 16
> connections. Most of the queries center around 3 tables that are about 1.5
> GB each.
>
>
> Thanks.
>    -Nick
>
> ---------------------------------------------------------------------
> Nick Fankhauser
>
>     nickf@doxpop.com  Phone 1.765.965.7363  Fax 1.765.962.9788
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