Date: Wed, 10 Oct 2012 12:10:12 -0400
From: Bruce Momjian <bruce@momjian.us>
To: Julien Cigar <jcigar@ulb.ac.be>
Cc: pgsql-performance@postgresql.org
Subject: Re: shared_buffers/effective_cache_size on 96GB server
Message-ID: <20121010161012.GE11892@momjian.us>
References: 
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	<50752DB2.6060004@ulb.ac.be>
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On Wed, Oct 10, 2012 at 10:11:30AM +0200, Julien Cigar wrote:
> On 10/10/2012 09:12, Strahinja Kustudić wrote:
> >Hi everyone,
> 
> Hello,
> 
> >
> >I have a Postgresql 9.1 dedicated server with 16 cores, 96GB RAM
> >and RAID10 15K SCSI drives which is runing Centos 6.2 x64. This
> >server is mainly used for inserting/updating large amounts of data
> >via copy/insert/update commands, and seldom for running select
> >queries.
> >
> >Here are the relevant configuration parameters I changed:
> >
> >shared_buffers = 10GB
> 
> Generally going over 4GB for shared_buffers doesn't help.. some of
> the overhead of bgwriter and checkpoints is more or less linear in
> the size of shared_buffers ..
> 
> >effective_cache_size = 90GB
> 
> effective_cache_size should be ~75% of the RAM (if it's a dedicated server)

Why guess?  Use 'free' to tell you the kernel cache size:

	http://momjian.us/main/blogs/pgblog/2012.html#May_4_2012

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +