From: Joost Kraaijeveld <J.Kraaijeveld@Askesis.nl>
To: PFC <lists@peufeu.com>
Cc: David Lang <david@lang.hm>
Cc: Richard Huxton <dev@archonet.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: x206-x225
Date: Sat, 11 Mar 2006 15:26:14 +0100
Message-ID: <1142087174.6634.32.camel@localhost> (raw)
In-Reply-To: <op.s58yeob1cigqcu@apollo13>
References: <GMEAJIDMNDKCIHMMHDFLCEKHDHAA.hjs@rmax.nl>
<441181C6.3040401@archonet.com>
<1142063378.6634.13.camel@localhost>
<Pine.LNX.4.62.0603102355550.23148@qnivq.ynat.uz>
<1142065029.6634.23.camel@localhost>
<op.s58yeob1cigqcu@apollo13>
On Sat, 2006-03-11 at 12:33 +0100, PFC wrote:
> >> each transaction requires a sync to the disk, a sync requires a real
> >> write (which you then wait for), so you can only do one transaction per
> >> rotation.
> > Not according to a conversation I had with Western Digital about the
>
>
> It depends if you consider that "written to the disk" means "data is
> somewhere between the OS cache and the platter" or "data is writter on the
> platter and will survive a power loss".
>
> Postgres wants the second option, of course.
I assume that for PostgreSQL "written to disk" is after fsync returned
successfully. In practice that could very well mean that the data is
still in a cache somewhere (controller or harddisk, not in the OS
anymore, see also man page of fsync)
--
Groeten,
Joost Kraaijeveld
Askesis B.V.
Molukkenstraat 14
6524NB Nijmegen
tel: 024-3888063 / 06-51855277
fax: 024-3608416
e-mail: J.Kraaijeveld@Askesis.nl
web: www.askesis.nl
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To: pgsql-performance@postgresql.org
Cc: J.Kraaijeveld@Askesis.nl, lists@peufeu.com, david@lang.hm, dev@archonet.com
Subject: Re: x206-x225
In-Reply-To: <1142087174.6634.32.camel@localhost>
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