Re: archive_timeout?

On Tue, 2006-10-10 at 22:26 +0900, Tatsuo Ishii wrote:
> If archive_timeout is set to non 0, it seems an archive log segment is
> created every time checkpoint occurs even there's no database
> updation. This leads to creating 16MB log segment files every 5
> minutes (default checkpoint period), which will in turn produce 4.6GB
> log segments with bogus data. Is this normal?
> 
> This is PostgreSQL 8.2 beta1.

If the WAL is pretty much empty, gzip brings it from 16MB down to about
16KB, which is much more reasonable. I've noticed that even when idle
there are a few files that seem to compress only to about 32KB, and some
only to 880KB. I don't know exactly why those files are different,
perhaps something with the stats collector? Autovacuum was off for this
test.

There should be a documentation note to let people know that the archive
will grow even when idle. Perhaps we should suggest compression in the
docs so that people don't get worried about many gigabytes of mostly-
empty files filling up their backup storage.

Regards,Jeff Davis