FW: Version 7 question - Mailing list pgsql-performance

What would be the best value range for effective_cache_size
on Postgres 7.3.2, assuming say 1.5 GB of RAM and
shared_buffers set to 8192, and shmmax set to 750mb?

And what are the most important factors one should take
into account in determining the value?



> -----Original Message-----
> From:    scott.marlowe [SMTP:scott.marlowe@ihs.com]
> Sent:    01 July 2003 02:56
> To:    Michael Mattox
> Cc:    Hilary Forbes; pgsql-performance@postgresql.org
> Subject:    Re: [PERFORM] Version 7 question
>
> 8192 is only 64 megs of RAM, not much, but a good number.  Keep in mind
> that the kernel tends to be better at buffering huge amounts of disk,
> while postgresql is better left to use buffers that are large enough for
> the current working set (i.e. not your whole database, just the largest
> amount of data you're slinging about on a regular basis in one query.)
>
> On a machine with 1.5 gig of RAM, I've found settings as high as 32768
> (256 megs of ram) to run well, but anything over that doesn't help.  Of
> course, we don't toss around more than a hundred meg or so at a time.   If
>
> our result sets were in the gigabyte range, I'd A: want more memory and B:
>
> Give more of it to postgresql.
>
> The original poster was, I believe running 7.0.x, which is way old, so no,
>
> I don't think there was an equivalent of effective_cache_size in that
> version.  Upgrading would be far easier than performance tuning 7.0. since
>
> the query planner was much simpler (i.e. more prone to make bad decisions)
>
> in 7.0.
>
> On Tue, 1 Jul 2003, Michael Mattox wrote:
>
> > I have my shared buffers at 8192 and my effective cache at 64000 (which
> is
> > 500 megs).  Depends a lot on how much RAM you have.  I have 1.5 gigs and
> > I've been asking my boss for another 512megs for over a month now.  I
> have
> > no idea if my buffers are too high/low.
> >
> > Michael
> >
> > > -----Original Message-----
> > > From: pgsql-performance-owner@postgresql.org
> > > [mailto:pgsql-performance-owner@postgresql.org]On Behalf Of Hilary
> > > Forbes
> > > Sent: Tuesday, July 01, 2003 2:10 PM
> > > To: pgsql-performance@postgresql.org
> > > Subject: [PERFORM] Version 7 question
> > >
> > >
> > > I'm just trying to improve performance on version 7 before doing
> > > some tests and hopefully upgrading to 7.3.
> > >
> > > At the moment we have
> > > B=64  (no  of shared buffers)
> > > N=32 (no of connections)
> > > in postmaster.opt which I take it is the equivalent of the new
> > > postgresql.conf file.
> > >
> > >  From all that is being written about later versions I suspect
> > > that this is far too low.  Would I be fairly safe in making the
> > > no of shared buffers larger?  Also is there an equivalent of
> > > effective_cache_size that I can set for version 7?
> > >
> > > Many thanks in advance
> > > Hilary
> > >
> > >
> > >
> > >
> > > Hilary Forbes
> > > -------------
> > > DMR Computer Limited:   http://www.dmr.co.uk/
> > > Direct line:  01689 889950
> > > Switchboard:  (44) 1689 860000  Fax: (44) 1689 860330
> > > E-mail:  hforbes@dmr.co.uk
> > >
> > > **********************************************************
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