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

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Simon Riggs <simon(at)2ndQuadrant(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #4879: bgwriter fails to fsync the file in recovery mode
Date: 2009-06-25 22:14:03
Message-ID: 4A43F6AB.9030607@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-bugs
Tom Lane wrote:
> The behavior you seem to have in mind would be completely disastrous
> from a performance standpoint, as we'd be writing and fsyncing
> pg_control constantly during a recovery.

Please define "constantly". We discussed that part of the patch here:

http://archives.postgresql.org/message-id/498AB55D.50408@enterprisedb.com

>  I wouldn't consider that a
> good idea from a reliability standpoint either --- the more writes to
> pg_control, the more risk of fatal corruption of that file.

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.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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Next:From: Heikki LinnakangasDate: 2009-06-25 22:18:37
Subject: Re: BUG #4879: bgwriter fails to fsync the file in recovery mode
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Subject: Re: BUG #4879: bgwriter fails to fsync the file in recovery mode

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