2014-12-30 18:45 GMT+01:00 Jeff Janes <jeff.ja...@gmail.com>: > On Tue, Dec 30, 2014 at 12:35 AM, Guillaume Lelarge < > guilla...@lelarge.info> wrote: > >> Sorry for my very late answer. It's been a tough month. >> >> 2014-11-27 0:00 GMT+01:00 Bruce Momjian <br...@momjian.us>: >> >>> On Mon, Nov 3, 2014 at 12:39:26PM -0800, Jeff Janes wrote: >>> > It looked to me that the formula, when descending from a previously >>> stressed >>> > state, would be: >>> > >>> > greatest(1 + checkpoint_completion_target) * checkpoint_segments, >>> > wal_keep_segments) + 1 + >>> > 2 * checkpoint_segments + 1 >>> >>> I don't think we can assume checkpoint_completion_target is at all >>> reliable enough to base a maximum calculation on, assuming anything >>> above the maximum is cause of concern and something to inform the admins >>> about. >>> >>> Assuming checkpoint_completion_target is 1 for maximum purposes, how >>> about: >>> >>> max(2 * checkpoint_segments, wal_keep_segments) + 2 * >>> checkpoint_segments + 2 >>> >>> >> Seems something I could agree on. At least, it makes sense, and it works >> for my customers. Although I'm wondering why "+ 2", and not "+ 1". It seems >> Jeff and you agree on this, so I may have misunderstood something. >> > > From hazy memory, one +1 comes from the currently active WAL file, which > exists but is not counted towards either wal_keep_segments nor towards > recycled files. And the other +1 comes from the formula for how many > recycled files to retain, which explicitly has a +1 in it. > >
OK, that seems much better. Thanks, Jeff. > -- Guillaume. http://blog.guillaume.lelarge.info http://www.dalibo.com
