On 2014-02-02 23:50:40 +0900, Fujii Masao wrote: > On Sun, Feb 2, 2014 at 5:49 AM, Andres Freund <and...@2ndquadrant.com> wrote: > > On 2014-01-24 22:31:17 +0900, MauMau wrote: > >> I haven't tried reducing checkpoint_timeout. > > > > Did you try reducing checkpoint_segments? As I pointed out, at least if > > standby_mode is enabled, it will also trigger checkpoints, independently > > from checkpoint_timeout. > > Right. If standby_mode is enabled, checkpoint_segment can trigger > the restartpoint. But the problem is that the timing of restartpoint > depends on not only the checkpoint parameters (i.e., > checkpoint_timeout and checkpoint_segments) that are used during > archive recovery but also the checkpoint WAL that was generated > by the master.
Sure. But we really *need* all the WAL since the last checkpoint's redo location locally to be safe. > For example, could you imagine the case where the master generated > only one checkpoint WAL since the last backup and it crashed with > database corruption. Then DBA decided to perform normal archive > recovery by using the last backup. In this case, even if DBA reduces > both checkpoint_timeout and checkpoint_segments, only one > restartpoint can occur during recovery. This low frequency of > restartpoint might fill up the disk space with lots of WAL files. I am not sure I understand the point of this scenario. If the primary crashed after a checkpoint, there won't be that much WAL since it happened... > > If the issue is that you're not using standby_mode (if so, why?), then > > the fix maybe is to make that apply to a wider range of situations. > > I guess that he is not using standby_mode because, according to > his first email in this thread, he said he would like to prevent WAL > from accumulating in pg_xlog during normal archive recovery (i.e., PITR). Well, that doesn't necessarily prevent you from using standby_mode... But yes, that might be the case. I wonder if we shouldn't just always look at checkpoint segments during !crash recovery. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers