Re: [DOCS] pg_total_relation_size() and CHECKPOINT

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, "Zubkovsky, Sergey" <Sergey(dot)Zubkovsky(at)transas(dot)com>, pgsql-hackers(at)postgresql(dot)org, Magnus Hagander <magnus(at)hagander(dot)net>
Subject: Re: [DOCS] pg_total_relation_size() and CHECKPOINT
Date: 2008-03-27 02:37:04
Message-ID: 47EB0850.1050805@dunslane.net
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Tom Lane wrote:
> Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
>
>> Tom Lane wrote:
>>
>>>> The real question here is whether Windows' stat() is telling the truth
>>>> about how much filesystem space has actually been allocated to a file.
>>>>
>>> One thing that would be good is just to see who else can reproduce
>>> the original observation:
>>> http://archives.postgresql.org/pgsql-docs/2008-03/msg00041.php
>>>
>
>
>> I have reproduced it in XP-Pro/SP2 running in a VMWare machine on an FC6
>> host.
>>
>
> OK, so the next question is do we really have an issue, or is this just
> an observational artifact? What I'd try is deliberately running the
> machine out of disk space with a long series of inserts, and then see
> whether subsequent checkpoint attempts fail due to ENOSPC errors while
> trying to write out dirty buffers.
>
> To avoid conflating this effect with anything else, it'd be best if you
> could put the DB on its own small partition, and *not* put pg_xlog
> there.
>
>
>

I'm working on this (thank goodness for junctions). Maybe we shopuld
look at providing a config setting for pg_xlog.

cheers

andrew

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