Re: Write cache

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От Andreas Pflug
Тема Re: Write cache
Дата
Msg-id 4016F163.60106@pse-consulting.de
обсуждение исходный текст
Ответ на Re: Write cache  (ohp@pyrenet.fr)
Ответы Re: Write cache  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-hackers
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





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