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Re: BUG #4879: bgwriter fails to fsync the file in recoverymode

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #4879: bgwriter fails to fsync the file in recoverymode
Date: 2009-06-26 04:40:45
Message-ID: 1245991245.4038.343.camel@ebony.2ndQuadrant (view raw or flat)
Thread:
Lists: pgsql-bugs
On Fri, 2009-06-26 at 10:56 +0900, Fujii Masao wrote:
> Hi,
> 
> Thank you for addressing the problem!
> 
> On Fri, Jun 26, 2009 at 7:14 AM, Heikki
> Linnakangas<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> > We certainly update it an order of magnitude more often than before, but
> > I don't think that's an issue. We're talking about archive recovery
> > here. It's not like in normal operation where a corrupt pg_control file
> > means that you lose your data. It will stop the server from starting up,
> > but there's many other files that can be corrupt in a way that causes
> > recovery to fail or stop too early.
> 
> Frequent updating of pg_control causes the significant performance
> degradation of archive recovery. I think that this is an issue to be fixed.
> The warm-standby users (including me) care about the performance
> of the standby server, because that affects the failover time, for example.

An important point.

The update rate "should" be once per clock cycle at most and should
occur in bgwriter not startup. If there is evidence of a problem then I
would support reducing the update rate. The purpose of the patch was
performance, not to fix an obscure and unreported inconsistency.

-- 
 Simon Riggs           www.2ndQuadrant.com
 PostgreSQL Training, Services and Support


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