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Re: Hot Backup with rsync fails at pg_clog if under load

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Florian Pflug <fgp(at)phlo(dot)org>
Cc: Daniel Farina <daniel(at)heroku(dot)com>, Chris Redekop <chris(at)replicon(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Hot Backup with rsync fails at pg_clog if under load
Date: 2011-10-26 11:43:07
Message-ID: CA+U5nMJLDZ7VP1O3Jdde+p+9-HxuEi8qG+v5+LuoZGSiOvhkxA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Oct 26, 2011 at 12:16 PM, Florian Pflug <fgp(at)phlo(dot)org> wrote:

>> Chris' clog error was caused by a file read error. The file was
>> opened, we did a seek within the file and then the call to read()
>> failed to return a complete page from the file.
>>
>> The xid shown is 22811359, which is the nextxid in the control file.
>>
>> So StartupClog() must have failed trying to read the clog page from disk.
>
> Yep.
>
>> That isn't a Hot Standby problem, a recovery problem nor is it certain
>> its a PostgreSQL problem.
>
> It's very likely that it's a PostgreSQL problem, though. It's probably
> not a pilot error since it happens even for backups taken with pg_basebackup(),
> so the only explanation other than a PostgreSQL bug is broken hardware or
> a pretty serious kernel/filesystem bug.

The way forwards here is for someone to show the clog file that causes
the error and find out why the call to read() fails.

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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