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Re: Write ahead logging

From: Matthias Meixner <meixner(at)dvs1(dot)informatik(dot)tu-darmstadt(dot)de>
To: Mario Weilguni <mweilguni(at)sime(dot)com>
Cc: Manfred Koizar <mkoi-pg(at)aon(dot)at>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Write ahead logging
Date: 2003-02-21 08:52:48
Message-ID: 3E55E8E0.60201@dvs1.informatik.tu-darmstadt.de (view raw or flat)
Thread:
Lists: pgsql-performance
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

-- 
Matthias Meixner                       meixner(at)informatik(dot)tu-darmstadt(dot)de
Technische Universit├Ąt Darmstadt
Datenbanken und Verteilte Systeme              Telefon (+49) 6151 16 6232
Wilhelminenstra├če 7, D-64283 Darmstadt, Germany    Fax (+49) 6151 16 6229


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