Subject: Re: archive wal's failure and load increase.
From: Simon Riggs <simon@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: cedric@dreamgnu.com, pgsql-performance@postgresql.org
In-Reply-To: <15270.1159540162@sss.pgh.pa.us>
References: <451C2572.20800@dreamgnu.com> <1159527513.2767.296.camel@holly>
	<15270.1159540162@sss.pgh.pa.us>
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Date: Fri, 29 Sep 2006 15:53:40 +0100
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On Fri, 2006-09-29 at 10:29 -0400, Tom Lane wrote:
> Simon Riggs <simon@2ndquadrant.com> writes:
> > We discussed putting PreallocXlogFiles() in bgwriter once before, but I
> > think last time we discussed that idea it was rejected, IIRC.
> 
> We already do that: it's called a checkpoint.  

Yes, but not enough.

PreallocXlogFiles() adds only a *single* xlog file, sometimes.

On a busy system, that would be used up too quickly to make a
difference. After that the effect of adding new files would continue as
suggested.

If it did add more than one... it might work better for this case.

> It's a good thought but I don't think the theory holds water for
> explaining Cedric's problem, unless there was *also* some effect
> preventing checkpoints from completing ... which would be a much more
> serious problem than the archiver failing.

Still the best explanation for me.

-- 
  Simon Riggs             
  EnterpriseDB   http://www.enterprisedb.com