Re: Why so many xlogs?

On Mon, Nov 01, 2010 at 08:13:49PM +0100, Cédric Villemain wrote:
> 2010/11/1 hubert depesz lubaczewski <depesz(at)depesz(dot)com>:
> > On Mon, Nov 01, 2010 at 07:22:50PM +0100, Cédric Villemain wrote:
> >> > as I understand, max number of xlog files in pg_xlog should be ( 1 + 2 *
> >> > checkpoint_segments ).
> >> (2 + checkpoint_completion_target) * checkpoint_segments + 1
> >> => 291
> >
> > this is formula gave to me by rhodiumtoad on irc, but we tested with lower
> > checkpoint_completion_target and it didn't change *anything*.
>
> You'll have between 211 and 291 files for 0.1 to 0.9
> checkpoint_completion_target.
> You'd have more than the number of files given by formula used during
> your tests ?

yes. we decreased checkpoint_completion_target to 0.5, and the numbers
of xlog segments *did not change*.

also - can you explain why "fraction of total time" (time!) would
directly relate to number of xlog files existing in pg_xlog? I mean -
you're not the first person to suggest it, but I don't see any way that
these two could be related.

Best regards,

depesz

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