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Re: Write cache

From: Andreas Pflug <pgadmin(at)pse-consulting(dot)de>
To: ohp(at)pyrenet(dot)fr
Cc: Larry Rosenman <ler(at)lerctr(dot)org>,pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Write cache
Date: 2004-01-27 23:16:51
Message-ID: 4016F163.60106@pse-consulting.de (view raw or flat)
Thread:
Lists: pgsql-hackers
ohp(at)pyrenet(dot)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




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