Date: Thu, 20 Jun 2002 14:56:12 -0700 From: Nick Sayer <nsayer@quack.kfu.com> To: pjklist@ekahuna.com Cc: stable@FreeBSD.ORG, Matthias Andree <matthias.andree@gmx.de> Subject: Re: ATA Atapi 4.6 Release Message-ID: <3D124F7C.6090302@kfu.com> References: <20020620211121029.AAA600@empty1.ekahuna.com@pc02.ekahuna.com>
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Philip J. Koenig wrote: > >Excuse my ignorance but I was under the impression that (at least >for SCSI) the sole function of tagged command queuing was to re-order >a string of drive commands in order to perform them more efficiently >- ie take into account sector position and latency to re-order things >like seeks. (ie "elevator sorting" or "elevator seeking") > >Why does this magically make write-back drive-caching "safe"? > Because the OS is notified when the write is actually completed. That makes it safe, because softupdates can insure that writes occur in a particular order (that is, write #2 is not scheduled until it is known that write #1 completes). To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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