From: Simon Riggs <simon@2ndquadrant.com>
To: Greg Smith <gsmith@gregsmith.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Estimating WAL volume
Date: Mon, 16 Jul 2007 09:02:08 +0100
Message-ID: <1184572928.5125.4.camel@ebony.site> (raw)
In-Reply-To: <Pine.GSO.4.64.0707112254480.17954@westnet.com>
References: <Pine.GSO.4.64.0707112254480.17954@westnet.com>
On Wed, 2007-07-11 at 23:10 -0400, Greg Smith wrote:
> All this talk of WAL writing lately has me wondering something I haven't
> spent enough time looking at the source to figure out myself this
> week...any good rules of thumb out there for estimating WAL volume? I'm
> used to just measuring it via benchmarking but it strikes me a formula
> would be nice to have for pre-planning.
>
> For example, if I have a table where a typical row is X bytes wide, and
> I'm updating Y of those per second, what's the expected write rate of WAL
> volume? Some % of those writes are going to be full pages; what's
> typical? How much does the number and complexity of indexes factor into
> things--just add the width of the index in bytes to the size of the
> record, or is it worse than that?
I published an analysis of WAL traffic from Greg Stark earlier, based
upon xlogdump.
http://archives.postgresql.org/pgsql-hackers/2007-03/msg01589.php
Other details of WAL volumes are in the code. Further analysis would be
welcome, to assist discussions of where to optimize next.
--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-performance@postgresql.org
Cc: simon@2ndquadrant.com, gsmith@gregsmith.com
Subject: Re: Estimating WAL volume
In-Reply-To: <1184572928.5125.4.camel@ebony.site>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox