Re: Configuration settings for 32GB RAM server

Thanks to all for the feedback on this issue.. After reviewing your comments, Im thinking of changing to the following values

shared_buffers = 786432 - If Ive done my math right, then this is 6GB which is 25% of 24GB ( I want to preserve the other 8GB for OS and App )

effective_cache_size = 2359296 - Equates to 18GB, which is 75% of 24GB.. Using the feedback from Dave Cramer

work_mem = 32768

maintenance_work_mem = 1048576 i.e. 1GB

max_fsm_relations = 10,000 - Given the small amount of memory this will use, I figure go large and not worry about it in the future.

max_fsm_pages = 10,000,000 - Again, increasing this significantly to cover my existing vacuuming numbers, and given I have a lot of memory, it seems like its not going to hurt me at all.

Sound good?

________________________________

From: Dave Cramer [mailto:pg(at)fastcrypt(dot)com]
Sent: 04 December 2006 23:29
To: Mark Lonsdale
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] Configuration settings for 32GB RAM server

On 4-Dec-06, at 12:10 PM, Mark Lonsdale wrote:

Hi

We are migrating our Postgres 7.3.4 application to postgres 8.1.5 and also moving it to a server with a much larger hardware configuration as well. The server will have the following specification.

- 4 physical CPUs (hyperthreaded to 8)

Try both hyperthreaded and not, there's been some evidence that HT helps us now

- 32 GB RAM

- x86_64 architecture

- RedHat AS 4

- postgres 8.1.5

Ive been taking a look at the various postgres tuning parameters, and have come up with the following settings.

shared_buffers - 50,000 - From what Id read, increasing this number higher than this wont have any advantages ?

This is no longer true, 25% of available memory is a good starting place, and go up from there

effective_cache_size = 524288 - My logic was I thought Id give the DB 16GB of the 32, and based this number on 25% of that number, sound okay?

this should be around 3/4 of available memory or 24G

work_mem - 32768 - I only have up to 30 connections in parallel, and more likely less than ½ that number. My sql is relatively simple, so figured even if there was 5 sorts per query and 30 queries in parallel, 32768 would use up 4GB of memory.. Does this number sound too high?

Maintenance_work_mem = 1048576 - Figured Id allocate 1GB for this.

fsm_relations = 2000 - I have about 200 tables plus maybe 4 or 5 indexes on each, and didn't want to have to worry about this number in future so doubled it.

fsm_pages = 200,000 - Based this on some statistics about the number of pages freed from a vacuum on older server. Not sure if its fair to calculate this based on vacuum stats of 7.3.4 server?

this is dependent on your application

Do these numbers look reasonable given the machine above? Any other settings that I should be paying particular consideration too?

autovacuum settings.

Thanks

Mark