Обсуждение: Data and logs on different physical drives - advantage?

"Weber, Johann (ISS Kassel)" <jweber@iss.net> writes:
> Is this true for PostgreSQL (V 8.0 on ReadHat)? My tests do not show any
> speed gained when placing pg_clog and pg_xlog on a different drive.

The conventional wisdom is that it's a win to have pg_xlog on a drive by
itself.  The above is not that.  pg_clog is more in the nature of data,
and in any case you lose the advantage as soon as the drive handling
pg_xlog has to move the head away from the current xlog file.

Whether any particular test case would show an advantage is another
question of course.  In a heavy-write scenario I would think you could
probably measure a win.

            regards, tom lane

 Thanks, after playing around a little I found that placing the indices
on a different drive gave a real performance increase in my scenario.
Johann


-----Original Message-----
From: Tom Lane [mailto:tgl@sss.pgh.pa.us]
Sent: Monday, October 10, 2005 4:35 PM
To: Weber, Johann (ISS Kassel)
Cc: pgsql-admin@postgresql.org
Subject: Re: [ADMIN] Data and logs on different physical drives -
advantage?

"Weber, Johann (ISS Kassel)" <jweber@iss.net> writes:
> Is this true for PostgreSQL (V 8.0 on ReadHat)? My tests do not show
> any speed gained when placing pg_clog and pg_xlog on a different
drive.

The conventional wisdom is that it's a win to have pg_xlog on a drive by
itself.  The above is not that.  pg_clog is more in the nature of data,
and in any case you lose the advantage as soon as the drive handling
pg_xlog has to move the head away from the current xlog file.

Whether any particular test case would show an advantage is another
question of course.  In a heavy-write scenario I would think you could
probably measure a win.

            regards, tom lane