From: Decibel! <decibel@decibel.org>
To: Mark Mielke <mark@mark.mielke.cc>
Cc: Scott Marlowe <scott.marlowe@gmail.com>
Cc: Gregory Stark <stark@enterprisedb.com>
Cc: Luke Lonergan <llonergan@greenplum.com>
Cc: Carlo Stonebanks <stonec.register@sympatico.ca>
Cc: pgsql-performance@postgresql.org
Subject: Re: random_page_costs - are defaults of 4.0 realistic for SCSI RAID 1
Date: Tue, 11 Sep 2007 16:26:34 -0500
Message-ID: <20070911212634.GE38801@decibel.org> (raw)
In-Reply-To: <46E5C38E.8030806@mark.mielke.cc>
References: <C30AF4C7.4230B%llonergan@greenplum.com>
<87y7fekxga.fsf@oxford.xeocode.com>
<dcc563d10709101459o11451c33y8cab7dcf1e00a93f@mail.gmail.com>
<46E5C38E.8030806@mark.mielke.cc>
On Mon, Sep 10, 2007 at 06:22:06PM -0400, Mark Mielke wrote:
> In my case, I set effective_cache_size to 25% of the RAM available to
> the system (256 Mbytes), for a database that was about 100 Mbytes or
> less. I found performance to increase when reducing random_page_cost
> from 4.0 to 3.0.
Just for the record, effective_cache_size of 25% is *way* too low in
most cases, though if you only have 1GB setting it to 500MB probably
isn't too far off.
Generally, I'll set this to however much memory is in the server, minus
1G for the OS, unless there's less than 4G of total memory in which case
I subtract less.
--
Decibel!, aka Jim Nasby decibel@decibel.org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
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To: pgsql-performance@postgresql.org
Cc: decibel@decibel.org, mark@mark.mielke.cc, scott.marlowe@gmail.com, stark@enterprisedb.com, llonergan@greenplum.com, stonec.register@sympatico.ca
Subject: Re: random_page_costs - are defaults of 4.0 realistic for SCSI RAID 1
In-Reply-To: <20070911212634.GE38801@decibel.org>
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