Re: Write ahead logging

From: Rod Taylor <rbt(at)rbt(dot)ca>
To: Matthias Meixner <meixner(at)dvs1(dot)informatik(dot)tu-darmstadt(dot)de>
Cc: Mario Weilguni <mweilguni(at)sime(dot)com>, Manfred Koizar <mkoi-pg(at)aon(dot)at>, Postgresql Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Write ahead logging
Date: 2003-03-06 23:35:56
Message-ID: 1046993755.487.86.camel@jester
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What were you using to measure the latency. Don't suppose you could
send it over. The admins locally don't like what I used to do the test
with -- they don't want to turn off write-caching for other reasons.

On Fri, 2003-02-21 at 03:52, Matthias Meixner wrote:
> Mario Weilguni wrote:
> >>>So the question is: has anybody verified, that the log is written to disk
> >>>before returning from commit?
> >>
> >>Some (or all?) IDE disks are known to lie: they report success as
> >>soon as the data have reached the drive's RAM.
> >
> >
> > under linux, hdparm -W can turn off the write cache of IDE disk, maybe you
> > should try with write-caching turned off.
>
> Yes, that made a big difference. Latency went up to 25-95ms.
>
> Regards,
>
> Matthias Meixner
--
Rod Taylor <rbt(at)rbt(dot)ca>

PGP Key: http://www.rbt.ca/rbtpub.asc

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