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Re: Write cache

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Write cache
Date: 2004-01-31 21:19:07
Message-ID: 200401312119.i0VLJ7W01821@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Andrew Dunstan wrote:
> 
> 
> Tom Lane wrote:
> 
> >Andreas Pflug <pgadmin(at)pse-consulting(dot)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(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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