Re: Fw: Help me put 2 Gigs of RAM to use

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Mark Stosberg wrote:
I find the file a bit hard to read because of the lack of units in the examples, but perhaps that's already been addressed in future
versions.

 max_connections        = 400 # Seems to be enough us
 shared_buffers         = 8192
 effective_cache_size   = 1000
 work_mem               = 4096
 maintenance_work_mem   = 160MB
It's already addressed in 8.2, as you can note by the fact that "maintenance_work_mem" is in there with an easy to read format. Guessing that someone either pulled in settings from an older version, or used some outdated web guide to get starter settings.

To convert the rest of them, you need to know what the units for each parameter is. You can find that out like this:

gsmith=# select name,setting,unit from pg_settings where name in ('shared_buffers','effective_cache_size','work_mem');

        name         | setting | unit
----------------------+---------+------
effective_cache_size | 16384   | 8kB
shared_buffers       | 4096    | 8kB
work_mem             | 1024    | kB

So your shared buffers setting is 8192 * 8K = 64MB
effective_cache_size is 8MB
work_mem is 4MB.

The first and last of those are reasonable but on the small side, the last is...not. Increasing it won't actually use more memory on your server though, it will just change query plans--so you want to be careful about increasing it too much in one shot.

The next set of stuff you need to know about general guidelines for server sizing is at http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server

You'd probably want to put shared_buffers at a higher level based on the amount of RAM on your server, but I'd suggest you tune the checkpoint parameters along with that--just increasing the buffer space along can cause problems rather than solve them if you're having checkpoints all the time.

--
Greg Smith    2ndQuadrant   Baltimore, MD
PostgreSQL Training, Services and Support
greg@xxxxxxxxxxxxxxx  www.2ndQuadrant.com


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