Re: BUG #4801: Performance failure: 600 MB written to each WAL log

On Fri, 2009-05-08 at 12:26 +0000, Peter Much wrote:

> Server becomes very slow while tremendous amounts of data are written
> to WAL logs - disk activity log shows 600 MB of effective write
> requests before each 16 MB WAL log is archived and recycled.

VACUUM FULL does many things, most of them slowly. It re-writes normal
database blocks setting hint bits, which are not WAL logged. This may
explain the figures you have.

8.2 is also a fairly poor performer with VACUUM and will cause many WAL
unnecessary flushes per WAL file. Not sure why you are using an old
release of PostgreSQL on a new BSD version, but if you upgrade
PostgreSQL and use VACUUM instead you will see improvement.

--
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support