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Re: choosing the right platform

From: "Jim C(dot) Nasby" <jim(at)nasby(dot)net>
To: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
Cc: Matthew Nuzum <cobalt(at)bearfruit(dot)org>,'Josh Berkus' <josh(at)agliodbs(dot)com>,'Pgsql-Performance' <pgsql-performance(at)postgresql(dot)org>
Subject: Re: choosing the right platform
Date: 2003-04-09 23:47:44
Message-ID: 20030409184744.W31861@flake.decibel.org (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, Apr 09, 2003 at 11:55:56AM -0600, scott.marlowe wrote:
> A couple more suggestions.  One is to never allocate more than 50% of your 
> memory to a database's shared buffers, i.e. let the OS buffer the disks en 
> masse, while the database should have a smaller buffer for the most recent 
> accesses.  This is because kernel caching is usually faster and more 
> efficient than the database doing it, and this becomes more an issue with 
> large chunks of memory, which both Linux and BSD are quite good at 
> caching, and postgresql, not so good.
 
That seems odd... shouldn't pgsql be able to cache information better
since it would be cached in whatever format is best for it, rather than
the raw page format (or maybe that is the best format). There's also the
issue of having to go through more layers of software if you're relying
on the OS caching. All the tuning info I've seen for every other
database I've worked with specifically recommends giving the database as
much memory as you possibly can, the theory being that it will do a much
better job of caching than the OS will.
-- 
Jim C. Nasby (aka Decibel!)                    jim(at)nasby(dot)net
Member: Triangle Fraternity, Sports Car Club of America
Give your computer some brain candy! www.distributed.net Team #1828

Windows: "Where do you want to go today?"
Linux: "Where do you want to go tomorrow?"
FreeBSD: "Are you guys coming, or what?"


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