Re: Write cache

On Tue, 27 Jan 2004, Larry Rosenman wrote:

> Date: Tue, 27 Jan 2004 15:55:49 -0600
> From: Larry Rosenman <ler@lerctr.org>
> To: ohp@pyrenet.fr
> Cc: pgsql-hackers list <pgsql-hackers@postgresql.org>
> Subject: Re: Write cache
>
>
>
> --On Tuesday, January 27, 2004 22:48:42 +0100 ohp@pyrenet.fr wrote:
>
> > On Tue, 27 Jan 2004, Larry Rosenman wrote:
> >
> >> Date: Tue, 27 Jan 2004 15:45:20 -0600
> >> From: Larry Rosenman <ler@lerctr.org>
> >> To: ohp@pyrenet.fr
> >> Cc: pgsql-hackers list <pgsql-hackers@postgresql.org>
> >> Subject: Re: Write cache
> >>
> >>
> >>
> >> --On Tuesday, January 27, 2004 22:43:34 +0100 ohp@pyrenet.fr wrote:
> >>
> >> > On Tue, 27 Jan 2004, Larry Rosenman wrote:
> >> >
> >> >> Date: Tue, 27 Jan 2004 15:38:30 -0600
> >> >> From: Larry Rosenman <ler@lerctr.org>
> >> >> To: ohp@pyrenet.fr, pgsql-hackers list <pgsql-hackers@postgresql.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...
>
>
> >  >
> >>
> >> >> Which driver(s)?
> >> >>
> >> > Guess... ADPU320
> >> Hrm.
> >>
> >> >> LER
> >> >>
> >> >>
> >> >> --On Tuesday, January 27, 2004 22:34:46 +0100 ohp@pyrenet.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@pyrenet.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@pyrenet.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@pyrenet.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@pyrenet.fr
------------------------------------------------------------------------------
Make your life a dream, make your dream a reality. (St Exupery)