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Re: Write cache

From: Larry Rosenman <ler(at)lerctr(dot)org>
To: ohp(at)pyrenet(dot)fr
Cc: pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Write cache
Date: 2004-01-27 22:02:40
Message-ID: 381680000.1075240960@lerlaptop-red.iadfw.net (view raw or flat)
Thread:
Lists: pgsql-hackers

--On Tuesday, January 27, 2004 23:01:45 +0100 ohp(at)pyrenet(dot)fr wrote:

> On Tue, 27 Jan 2004, Larry Rosenman wrote:
>
>> Date: Tue, 27 Jan 2004 15:55:49 -0600
>> From: Larry Rosenman <ler(at)lerctr(dot)org>
>> To: ohp(at)pyrenet(dot)fr
>> Cc: pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>
>> Subject: Re: Write cache
>>
>>
>>
>> --On Tuesday, January 27, 2004 22:48:42 +0100 ohp(at)pyrenet(dot)fr wrote:
>>
>> > On Tue, 27 Jan 2004, Larry Rosenman wrote:
>> >
>> >> Date: Tue, 27 Jan 2004 15:45:20 -0600
>> >> From: Larry Rosenman <ler(at)lerctr(dot)org>
>> >> To: ohp(at)pyrenet(dot)fr
>> >> Cc: pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>
>> >> Subject: Re: Write cache
>> >>
>> >>
>> >>
>> >> --On Tuesday, January 27, 2004 22:43:34 +0100 ohp(at)pyrenet(dot)fr wrote:
>> >>
>> >> > On Tue, 27 Jan 2004, Larry Rosenman wrote:
>> >> >
>> >> >> Date: Tue, 27 Jan 2004 15:38:30 -0600
>> >> >> From: Larry Rosenman <ler(at)lerctr(dot)org>
>> >> >> To: ohp(at)pyrenet(dot)fr, pgsql-hackers list
>> >> >> <pgsql-hackers(at)postgresql(dot)org> Subject: Re: Write cache
>> >> >>
>> >> >> IDE or SCSI?
>> >> > SCSI
>> >> >>
>> >> >> Why do you think the WC is screwing you?
>> >> >>
>> >> > Because after a sys crash, the most used filesystems (databases) are
>> >> > screwed
>> >> what VxFS mount options are you using?
>> > Nothing special... And any option I could use would'nt change a thing:
>> > the cache is on the disk itself... I did'nt look physicaly yet but
>> > according to the docs there's no way to disable it lik I always did on
>> > IBM...
>> >
>> > I was forced to buy those disk (more expensive, not better)
>> define not special?
>>
>> ISTM that the driver should force it out to the disk, unless the disk is
>> lying to the driver, or the driver is buggy.
> That's exactly what I think: the DISK has a write cache so it's lying to
> the controler saying data is written when it's only in the disk cache.
>
> That also would explain the fantastic write performance I have compared to
> read...
SO, I consider these disks buggy or not acceptable for use.

LER

>>
>>
>> >  >
>> >>
>> >> >> Which driver(s)?
>> >> >>
>> >> > Guess... ADPU320
>> >> Hrm.
>> >>
>> >> >> LER
>> >> >>
>> >> >>
>> >> >> --On Tuesday, January 27, 2004 22:34:46 +0100 ohp(at)pyrenet(dot)fr wrote:
>> >> >>
>> >> >> > Because I've lost a lot of data using postgresql (and I know for
>> >> >> > sure this should'nt happen) I've gone a bit further reading
>> >> >> > documentations on my disks and...
>> >> >> >
>> >> >> > I have FUJITSU MAP3367NC 36G 10000 rpm disks, those disk have a
>> >> >> > write cache of 8Mb, if someone could tell me hox to turn it
>> >> >> > off... Could'nt find it in the docs and this could very well
>> >> >> > explain why a busy database crashes every time
>> >> >> >
>> >> >> > Thanks for your help
>> >> >> >
>> >> >> > --
>> >> >> > Olivier PRENANT        	        Tel: +33-5-61-50-97-00 (Work)
>> >> >> > 6, Chemin d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
>> >> >> > 31190 AUTERIVE                       +33-6-07-63-80-64 (GSM)
>> >> >> > FRANCE                          Email: ohp(at)pyrenet(dot)fr
>> >> >> > ----------------------------------------------------------------
>> >> >> > --- --- --- ----- Make your life a dream, make your dream a
>> >> >> > reality. (St Exupery)
>> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >
>> >> > --
>> >> > Olivier PRENANT        	        Tel: +33-5-61-50-97-00 (Work)
>> >> > 6, Chemin d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
>> >> > 31190 AUTERIVE                       +33-6-07-63-80-64 (GSM)
>> >> > FRANCE                          Email: ohp(at)pyrenet(dot)fr
>> >> > -------------------------------------------------------------------
>> >> > --- --- ----- Make your life a dream, make your dream a reality. (St
>> >> > Exupery)
>> >>
>> >>
>> >>
>> >>
>> >
>> > --
>> > Olivier PRENANT        	        Tel: +33-5-61-50-97-00 (Work)
>> > 6, Chemin d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
>> > 31190 AUTERIVE                       +33-6-07-63-80-64 (GSM)
>> > FRANCE                          Email: ohp(at)pyrenet(dot)fr
>> > ----------------------------------------------------------------------
>> > --- ----- Make your life a dream, make your dream a reality. (St
>> > Exupery)
>>
>>
>>
>>
>
> --
> Olivier PRENANT        	        Tel: +33-5-61-50-97-00 (Work)
> 6, Chemin d'Harraud Turrou           +33-5-61-50-97-01 (Fax)
> 31190 AUTERIVE                       +33-6-07-63-80-64 (GSM)
> FRANCE                          Email: ohp(at)pyrenet(dot)fr
> -------------------------------------------------------------------------
> ----- Make your life a dream, make your dream a reality. (St Exupery)



-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler(at)lerctr(dot)org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749

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