The postgresql.conf says that the maximum checkpoint_timeout is 1 hour. However, the following messages seem to suggest that it may be useful to set the value significantly higher to reduce unnecessary WAL volume: http://archives.postgresql.org/pgsql-hackers/2006-10/msg00527.php http://archives.postgresql.org/pgsql-hackers/2006-08/msg01190.php Is there a reason for the hour-long limit on checkpoint_timeout? Is there a cost to doing so, aside from potentially longer recovery time? As I understand it, the background writer keeps the I/O more balanced anyway, avoiding I/O spikes at checkpoint. I don't need the checkpoint time to be higher than 1 hour, but I'm trying to understand the reasoning behind the limit and the implications of a longer checkpoint_timeout. The docs here: http://www.postgresql.org/docs/current/static/wal-configuration.html say that checkpoints cause extra disk I/O. Is there a good way to measure how much extra I/O (and WAL volume) is caused by the checkpoints? Also, it would be good to know how much total I/O is caused by a checkpoint so that I know if bgwriter is doing it's job. Regards, Jeff Davis
