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)

Tue, 27 Jan 2004 22:34:46 +0100 (MET)
ohp@pyrenet.fr
Write cache
IDE or SCSI?

Why do you think the WC is screwing you?

Which driver(s)?

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)



-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749
Tue, 27 Jan 2004 15:38:30 -0600
Larry Rosenman <ler@lerctr.org>
Re: Write cache
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
> Which driver(s)?
>
Guess... ADPU320
> 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)

Tue, 27 Jan 2004 22:43:34 +0100 (MET)
ohp@pyrenet.fr
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?


>> 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)



-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749
Tue, 27 Jan 2004 15:45:20 -0600
Larry Rosenman <ler@lerctr.org>
Re: Write cache
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)
 >
>
> >> 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)

Tue, 27 Jan 2004 22:48:42 +0100 (MET)
ohp@pyrenet.fr
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.


>  >
>>
>> >> 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)



-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749
Tue, 27 Jan 2004 15:55:49 -0600
Larry Rosenman <ler@lerctr.org>
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)

Tue, 27 Jan 2004 23:01:45 +0100 (MET)
ohp@pyrenet.fr
Re: Write cache
--On Tuesday, January 27, 2004 23:01:45 +0100 ohp@pyrenet.fr wrote:

> 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...
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@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)



-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749
Tue, 27 Jan 2004 16:02:40 -0600
Larry Rosenman <ler@lerctr.org>
Re: Write cache
On Tue, 27 Jan 2004, Larry Rosenman wrote:

> Date: Tue, 27 Jan 2004 16:02:40 -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 23:01:45 +0100 ohp@pyrenet.fr wrote:
>
> > 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...
> SO, I consider these disks buggy or not acceptable for use.
So do I... I have 6 disks... 250$ each...
>
> LER
>
> >>
> >>
> >> >  >
> >> >>
> >> >> >> 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)
>
>
>
>

-- 
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)

Tue, 27 Jan 2004 23:03:56 +0100 (MET)
ohp@pyrenet.fr
Re: Write cache
--On Tuesday, January 27, 2004 23:03:56 +0100 ohp@pyrenet.fr wrote:

> On Tue, 27 Jan 2004, Larry Rosenman wrote:
>
>> Date: Tue, 27 Jan 2004 16:02:40 -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 23:01:45 +0100 ohp@pyrenet.fr wrote:
>>
>> > 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...
>> SO, I consider these disks buggy or not acceptable for use.
> So do I... I have 6 disks... 250$ each...
What kind of warranty?

How Old?


>>
>> LER
>>
>> >>
>> >>
>> >> >  >
>> >> >>
>> >> >> >> 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)
>>
>>
>>
>>
>
> --
> 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)



-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749
Tue, 27 Jan 2004 16:06:03 -0600
Larry Rosenman <ler@lerctr.org>
Re: Write cache
On Tue, 27 Jan 2004, Larry Rosenman wrote:
> >> >>
> >> >> 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.
> > So do I... I have 6 disks... 250$ each...
> What kind of warranty?
3 years 24 hours on site (the computer altogather)
>
> How Old?
>
3 months

-- 
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)

Tue, 27 Jan 2004 23:15:09 +0100 (MET)
ohp@pyrenet.fr
Re: Write cache
--On Tuesday, January 27, 2004 23:15:09 +0100 ohp@pyrenet.fr wrote:

> On Tue, 27 Jan 2004, Larry Rosenman wrote:
>> >> >>
>> >> >> 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.
>> > So do I... I have 6 disks... 250$ each...
>> What kind of warranty?
> 3 years 24 hours on site (the computer altogather)

>>
>> How Old?
>>
> 3 months
>
I'd tell them to get you disks that don't lie.

and be FIRM about it.

LER



-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 972-414-9812                 E-Mail: ler@lerctr.org
US Mail: 1905 Steamboat Springs Drive, Garland, TX 75044-6749
Tue, 27 Jan 2004 16:16:08 -0600
Larry Rosenman <ler@lerctr.org>
Re: Write cache
ohp@pyrenet.fr wrote:

>>>>>>
>>>>>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.
>>>
>>>      
>>>

This would be the first time a SCSI disk lies about its write caching. 
There are plenty of low-cost (i.e. IDE) disks out there having a hidden 
write cache, but AFAIK a generic SCSI tool is usable to enable/disable 
the write cache. I'd be quite surprised if your disks wouldn't allow 
disabling write caching, because SCSI disks are usually targeted towards 
professional usage.

Regards,
Andreas




Wed, 28 Jan 2004 00:16:51 +0100
Andreas Pflug <pgadmin@pse-consulting.de>
Re: Write cache
Andreas Pflug <pgadmin@pse-consulting.de> writes:
> This would be the first time a SCSI disk lies about its write caching. 
> There are plenty of low-cost (i.e. IDE) disks out there having a hidden 
> write cache, but AFAIK a generic SCSI tool is usable to enable/disable 
> the write cache.

A SCSI disk shouldn't lie about write completion in any case; there's no
need to because the interface spec is inherently multi-threaded (unlike
IDE).  See past discussions.

			regards, tom lane

Tue, 27 Jan 2004 19:09:57 -0500
Tom Lane <tgl@sss.pgh.pa.us>
Re: Write cache 


Tom Lane wrote:

>Andreas Pflug <pgadmin@pse-consulting.de> writes:
>  
>
>>This would be the first time a SCSI disk lies about its write caching. 
>>There are plenty of low-cost (i.e. IDE) disks out there having a hidden 
>>write cache, but AFAIK a generic SCSI tool is usable to enable/disable 
>>the write cache.
>>    
>>
>
>A SCSI disk shouldn't lie about write completion in any case; there's no
>need to because the interface spec is inherently multi-threaded (unlike
>IDE).  See past discussions.
>
>  
>
Unless I am reading it wrong,

http://www.fcpa.com/download/download/hard-drives/map10krpm-manual.pdf 
appears to suggest (page 5-21) that the write cache can be disabled. How 
I am not sure - maybe using one of the tools Andreas mentioned.

cheers

andrew




Tue, 27 Jan 2004 19:40:24 -0500
Andrew Dunstan <andrew@dunslane.net>
Re: Write cache
> Olivier PRENANT writes...
> 
> 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...
> 

The bottom line here is that Olivier has lost some data and I'm sure we
all want to know if there is a bug in PostgreSQL, or he has a hardware
problem. However, PostgreSQL is partially implicated only because it
discovered the error, but hasn't in any other way been associated yet
with the fatal crash itself.

My intuition tells me that this is hardware related. We've discussed
some probable causes, but nobody has come up with a diagnostic test to
evaluate the disks accuracy. This might be because this forum isn't the
most appropriate place to discuss disk storage or linux device drivers?
 
Olivier: if your disks are supported or under warranty, then my advice
would be to contact these people and ask for details of a suitable
diagnostic test, or go via their support forums to research this.
Expensive disks are usually fairly well supported, especially if they
smell an upgrade. :)

My experience with other RDBMS vendor's support teams is that they give
out this advice regularly when faced with RDBMS-reported data corruption
errors: "check your disks are working"; I think it is reasonable to do
the same here. Data corruption by the dbms does occur, but my experience
is that this is frequent than hardware-related causes. In the past, I
have used the dd command to squirt data at the disk, then read it back
again - but there may be reasons I don't know why a success on that test
might not be conclusive, so I personally would be happy to defer to
someone that does. I've seen errors like this come from soon-to-fail
disks, poor device drivers, failing non-volatile RAM, cabinet backplane
noise, poorly wired cabling and intermittently used shared SCSI...

Best of luck, Simon Riggs


Wed, 28 Jan 2004 14:56:40 -0000
"Simon Riggs" <simon@2ndquadrant.com>
Re: Write cache
Hi Simon,

Sorry I couldn't answer sooner.
Hope your daughter is OK by now.

On Wed, 28 Jan 2004, Simon Riggs wrote:

> Date: Wed, 28 Jan 2004 14:56:40 -0000
> From: Simon Riggs <simon@2ndquadrant.com>
> To: ohp@pyrenet.fr, 'pgsql-hackers list' <pgsql-hackers@postgresql.org>
> Subject: RE: [HACKERS] Write cache
>
> > Olivier PRENANT writes...
> >
> > 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...
> >
>
> The bottom line here is that Olivier has lost some data and I'm sure we
> all want to know if there is a bug in PostgreSQL, or he has a hardware
> problem. However, PostgreSQL is partially implicated only because it
> discovered the error, but hasn't in any other way been associated yet
> with the fatal crash itself.
I agree I MAY have an hardware problem. What happens is more a system
freeze than a system crash (there's no panic, no nothing, just freezes, no
disk activity, not network)

What bothers me is that the fs itself was badly hurt, although fsck did
repair errors, postgresql complained that it could'nt read a file
(relation) that obviously had a wrong block number somewhere.

Now, what puzzle me is that my fs are all vxfs, with an intent log.
Fairly like postgres.
In that case, how can I loose data with it?

Also I have mysql on the same filesystem (although VERY quiet) and it
did'nt suffer.

Postgresql is doing a LOT of job here, and since I host this very busy
database I experience data loose in case of crash.

This is NOT intended to start a war, I love postgres and I'm very
confident in it, but I may have a configuration where ch.. happens.
(like the 32 WAL buffers I have)

Likewise, I'd like to understand that statistic buffer full condition
 >
> My intuition tells me that this is hardware related. We've discussed
> some probable causes, but nobody has come up with a diagnostic test to
> evaluate the disks accuracy. This might be because this forum isn't the
> most appropriate place to discuss disk storage or linux device drivers?
>
> Olivier: if your disks are supported or under warranty, then my advice
> would be to contact these people and ask for details of a suitable
> diagnostic test, or go via their support forums to research this.
> Expensive disks are usually fairly well supported, especially if they
> smell an upgrade. :)
>
According to my vendor, there is NO write cache, and the system freeze is
the heart of the problem

> My experience with other RDBMS vendor's support teams is that they give
> out this advice regularly when faced with RDBMS-reported data corruption
> errors: "check your disks are working"; I think it is reasonable to do
> the same here. Data corruption by the dbms does occur, but my experience
> is that this is frequent than hardware-related causes. In the past, I
> have used the dd command to squirt data at the disk, then read it back
> again - but there may be reasons I don't know why a success on that test
> might not be conclusive, so I personally would be happy to defer to
> someone that does. I've seen errors like this come from soon-to-fail
> disks, poor device drivers, failing non-volatile RAM, cabinet backplane
> noise, poorly wired cabling and intermittently used shared SCSI...
The problem is that while the system is up and running, I have no log of
any error, it goes very fast does it's job correctly.
>
> Best of luck, Simon Riggs
>
>
Many thanks to all for your help

Regards
-- 
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)

Wed, 28 Jan 2004 18:25:59 +0100 (MET)
ohp@pyrenet.fr
Re: Write cache
On Wed, 28 Jan 2004 ohp@pyrenet.fr wrote:

> I agree I MAY have an hardware problem. What happens is more a system
> freeze than a system crash (there's no panic, no nothing, just freezes, no
> disk activity, not network)

I would suspect either bad hardware,a flakey SCSI driver, or a possible 
kernel bug.  If your system is freezing hard, it is NOT postgresql's 
fault.  It simply doesn't have the access to the kind of system resources 
needed to freeze a machine.

Is there a different SCSI driver / card you can try in there?  We've (and 
many others have too) had good luck with the LSI/MegaRAID cards and both 
the older 1.18 seris and new 2.x series drivers.  No freezes, no crashes, 
no hangs on the boxes with those in them.


Wed, 28 Jan 2004 10:57:51 -0700 (MST)
"scott.marlowe" <scott.marlowe@ihs.com>
Re: Write cache

"Simon Riggs" <simon@2ndquadrant.com> writes:

> In the past, I have used the dd command to squirt data at the disk, then
> read it back again - but there may be reasons I don't know why a success on
> that test might not be conclusive, so I personally would be happy to defer
> to someone that does.

Well that's an interesting tangent.

1) I've seen bad memory on a scsi controller once. Caused one-bit errors in
   data read back after being written. a dd might or might not find that
   depending on the buffer usage pattern, and depending on the pattern being
   written and read. Memory errors are notoriously fickle and can sometimes be
   triggered only by particular bit patterns in adjacent memory addresses in
   rapid succession.

   badblocks does try to address this by writing four different complementary
   patterns. but I'm not convinced it's really conclusive either. It's
   certainly not as sophisticated as memtest86 and can't really since it can't
   directly control the placement of data in the disk's buffers.

2) The disk could be finding lots of bad blocks during the dd run and
   remapping them. It gives no information to the OS through the regular
   interfaces. A low level diagnostic program can inquire about how many
   blocks have been remapped and how many spare blocks are available.

I know Maxtor is hot to have you run their PowerMax(tm) program whenever you
call tech support. I think it just runs something similar to badblocks and
asks the disk firmware if it's detected any low level problems.

In theory it can check things like the drive having trouble syncing to tracks
due to environmental factors like noise, vibrations, and heat. I don't know if
it does or not though.

-- 
greg


28 Jan 2004 13:52:07 -0500
Greg Stark <gsstark@mit.edu>
Re: Write cache
Andrew Dunstan wrote:
> 
> 
> Tom Lane wrote:
> 
> >Andreas Pflug <pgadmin@pse-consulting.de> writes:
> >  
> >
> >>This would be the first time a SCSI disk lies about its write caching. 
> >>There are plenty of low-cost (i.e. IDE) disks out there having a hidden 
> >>write cache, but AFAIK a generic SCSI tool is usable to enable/disable 
> >>the write cache.
> >>    
> >>
> >
> >A SCSI disk shouldn't lie about write completion in any case; there's no
> >need to because the interface spec is inherently multi-threaded (unlike
> >IDE).  See past discussions.
> >
> >  
> >
> Unless I am reading it wrong,
> 
> http://www.fcpa.com/download/download/hard-drives/map10krpm-manual.pdf 
> appears to suggest (page 5-21) that the write cache can be disabled. How 
> I am not sure - maybe using one of the tools Andreas mentioned.

My guess is to look for scsicmd or something like that.  The man page
usually talks about how to dump the device parametes.  Do that and you
should see something clear.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
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Sat, 31 Jan 2004 16:19:07 -0500 (EST)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Write cache