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Re: optimizing selects on time-series data in Pg

From: Aditya <aditya(at)grot(dot)org>
To: sfpug(at)postgresql(dot)org
Subject: Re: optimizing selects on time-series data in Pg
Date: 2003-08-12 16:44:48
Message-ID: 20030812164448.GA27175@mighty.grot.org (view raw or flat)
Thread:
Lists: sfpug
On Mon, Aug 11, 2003 at 08:50:32PM -0700, Sean Chittenden wrote:
> > >   shared_buffers = 128        # 2*max_connections, min 16 (default 64)
> > >   ...
> > >   #effective_cache_size = 1000  # default in 8k pages
> > 
> > You could certainly stand to raise these, unless your system is low
> > on RAM ...
> 
> Using /bin/sh, plop the following in to determine your
> effective_cache_size:
> 
> echo "effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))"

Thanks for that -- it shows:

  effective_cache_size = 7752

when I run it. That's a third smaller than what Josh recommended:

  set effective_cache_size to the expected available kernel cache, say 192mb =
  24576

> > > PIII-800/512MB RAM running FreeBSD 4-STABLE with the database data
> > > files NFS mounted via a 100Mbps/full-duplex private network from a
> > > lightly-loaded Network Appliance F87 fileserver (I'm pretty
> > > certain that we're not IO bound).
> 
> FWIW, NFS + DB server is a bad idea for file locking reasons.  -sc

even if there is only one database reader/writer? I've been using this setup
for a couple of years now without any untoward effects...

Thanks,
Adi

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Next:From: Josh BerkusDate: 2003-08-12 16:54:14
Subject: Re: optimizing selects on time-series data in Pg
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Subject: Re: optimizing selects on time-series data in Pg

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