Re: Curiosity: what is PostgreSQL doing with data when "nothing" is happening?

Gavan Schneider <pg-gts@snkmail.com> writes:
> On Saturday, November 24, 2012 at 04:18, Tom Lane wrote:
>> In the base configuration, an idle Postgres installation won't generate
>> any fresh WAL; but this isn't true if you've got hot-standby replication
>> configured, because of the effect described here:
>> http://archives.postgresql.org/pgsql-hackers/2011-10/msg00207.php
>> ....
>> You might want to reconsider those settings: the combination
>> of hot standby and archive timeout seems a bit redundant to me.  If
>> you're relying on a hot standby then you don't really need to worry
>> about keeping the WAL archive fully up-to-date, and contrarily if you
>> aren't using a hot standby then you should back off the wal_level
>> setting to eliminate unnecessary WAL traffic.

> But no hot standby...

Yeah, I took a second look and realized that you'd get this effect even
without hot_standby --- it's the alternation of checkpoint records and
forced segment switches from archive_timeout that creates the effect.

If you're concerned about minimizing WAL traffic at idle, you might want
to think about setting up a streaming replication arrangement instead of
relying on archive segment switches.  archive_timeout is really kind
of a hack.

            regards, tom lane