| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Peter Much <pmc(at)citylink(dot)dinoex(dot)sub(dot)org> |
| Cc: | pgsql-bugs(at)postgresql(dot)org |
| Subject: | Re: BUG #4801: Performance failure: 600 MB written to each WAL log |
| Date: | 2009-05-08 18:15:19 |
| Message-ID: | 1241806519.3843.47.camel@ebony.2ndQuadrant |
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| Thread: | |
| Lists: | pgsql-bugs |
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
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