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Date: Tue, 30 Mar 2010 09:23:49 -0600
Message-ID: <37d451f71003300823n2b9e3707n16676c41cb8883a9@mail.gmail.com>
Subject: Re: Migrate postgres to newer hardware
From: Rosser Schwarz <rosser.schwarz@gmail.com>
To: Renato Oliveira <renato.oliveira@grant.co.uk>
Cc: Tino Schwarze <postgresql@tisc.de>,
	"pgsql-admin@postgresql.org" <pgsql-admin@postgresql.org>
Content-Type: text/plain; charset=ISO-8859-1

On Tue, Mar 30, 2010 at 8:51 AM, Renato Oliveira
<renato.oliveira@grant.co.uk> wrote:
> If I use postgres 32 bit will it benefit from the extra memory on the system?

Indirectly, yes.  No individual PG process will be able to address
more than 4 gbytes of memory.  Assuming you have a 64-bit OS living
underneath, however, that may not matter much.  You'll potentially be
somewhat constrained in the sane values you can use for shared_buffers
(which, on a 16 gbyte box for example, I'd probably start in the 4
gbyte range and tune from there -- not an option in a 32-bit install).

But leaving aside effective_cache_size (and, as mentioned, potentially
shared_buffers), none of your config values are likely to approach the
4 gbyte boundary -- and in the case of effective_cache_size, that
isn't actually directly addressed by postgres, anyway.  It's just used
by the planner to calculate the likelihood of a given page it needs
being in the OS buffer cache, instead of on disk.

I've had production systems with a 32-bit postgres running quite
happily on a 64-bit OS.

rls

-- 
:wq