Re: Moving postgresql.conf tunables into 2003...

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Sean Chittenden <sean(at)chittenden(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Moving postgresql.conf tunables into 2003...
Date: 2003-07-05 22:58:25
Message-ID: 200307051558.25484.josh@agliodbs.com
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Sean,

> The SGML docs aren't in the DBA's face and are way out of the way for
> DBAs rolling out a new system or who are tuning the system. SGML ==
> Developer, conf == DBA.

That's exactly my point. We cannot provide enough documentation in the CONF
file without septupling its length. IF we remove all commentary, and instead
provide a pointer to the documentation, more DBAs will read it.

> Some of those parameters are based on
> hardware constraints and should be pooled and organized as such.
>
> random_page_cost ==
> avg cost of a random disk seek/read (eg: disk seek time) ==
> constant integer for a given piece of hardware

But, you see, this is exactly what I'm talking about. random_page_cost isn't
static to a specific piece of hardware ... it depends as well on what else is
on the disk/array, concurrent disk activity, disk controller settings,
filesystem, OS, distribution of records and tables, and arrangment of the
partitions on disk. One can certainly get a "good enough" value by
benchmarking the disk's random seek and calculating based on that ... but to
get an "ideal" value requires a long interactive session by someone with
experience and in-depth knowledge of the machine and database.

> There are other settings that are RAM based as well, which should be
> formulaic and derived though a formula hasn't been defined to date.

You seem pretty passionate about this ... how about you help me an Kevin
define a benchmarking suite when I get back into the country (July 17)? If
we're going to define formulas, it requires that we have a near-comprehensive
and consistent test database and test battery that we can run on a variety of
machines and platforms.

--
-Josh Berkus

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