From: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
---|---|
To: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #4879: bgwriter fails to fsync the file in recovery mode |
Date: | 2009-06-26 06:22:04 |
Message-ID: | 4A44690C.4090202@enterprisedb.com |
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Lists: | pgsql-bugs |
Fujii Masao wrote:
> 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.
Are you actually seeing performance degradation caused by frequent
pg_control updates? In the simple test scenarios I've tested, pg_control
is updated only once every few WAL segments, and this with
shared_buffer=32MB. With larger shared_buffers, it happens even less
frequently.
There's a DEBUG2-line in UpdateMinRecoveryPoint() that you can bump to
LOG level if you want to observe that behavior.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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