Re: Postgres low end processing. - Mailing list pgsql-performance

From Josh Berkus
Subject Re: Postgres low end processing.
Date
Msg-id 200310061121.20681.josh@agliodbs.com
Whole thread Raw
In response to Re: Postgres low end processing.  (Stef <svb@ucs.co.za>)
List pgsql-performance
Stef,

> => 1. Make sure that the WAL files (pg_xlog) are on a seperate disk from the
> => database files, either through mounting or symlinking.
>
> I'm not sure I understand how this helps?

It gives you better fsync write performance on a low-end disk setup.
Otherwise, the disk is forced to do a hop-back-and-forth between the database
and the xlog, resulting in much slower updates and thus the database tying up
blocks of RAM longer -- particularly if your shared_buffers are set very low,
which they will be.

On RAID setups, this is unnecessary becuase the RAID takes care of disk access
management.  But on a low-end, 2-IDE-disk machine, you have to do it.

--
-Josh Berkus
 Aglio Database Solutions
 San Francisco


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