Date: Tue, 8 Apr 2003 16:15:47 +0200 From: Alexander Leidinger <Alexander@Leidinger.net> To: Dag-Erling Smorgrav <des@ofug.org> Cc: sos@freebsd.org Subject: Re: cvs commit: src/sys/dev/ata ata-all.c ata-all.h ata-chipset.cata-dma.c ata-pci.c ata-pci.h Message-ID: <20030408161547.1963e23a.Alexander@Leidinger.net> In-Reply-To: <xzpfzot9jrw.fsf@flood.ping.uio.no> References: <20030408152227.60c38ce3.Alexander@Leidinger.net> <200304081327.h38DR9XC025406@spider.deepcore.dk> <20030408153259.2a4b03ac.Alexander@Leidinger.net> <xzpfzot9jrw.fsf@flood.ping.uio.no>
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On Tue, 08 Apr 2003 15:54:43 +0200 Dag-Erling Smorgrav <des@ofug.org> wrote: > Alexander Leidinger <Alexander@Leidinger.net> writes: > > Does this mean we can't use ATA-TQ in situations where we would use TQ > > without WC on a SCSI system (read: does it affect softupdates)? > > Tagged queueing doesn't make sense without a write cache. Think about > it for a minute. It doesn't make sense without some kind of a buffer, I know. With SCSI disks you can observe a small difference between TQ with WC enabled and TQ with WC disabled. Based upon this I concluded, that SCSI disks seems to have a buffer for the WC (with all it's ill side effects in the softupdates case) and another buffer for TQ. SCSI != ATA, but why design another WC/TQ combination, if I can borrow it from the SCSI disks... Feel free to correct misunderstandings on my side. Bye, Alexander. -- "One world, one web, one program" -- Microsoft promotional ad "Ein Volk, ein Reich, ein Fuehrer" -- Adolf Hitler http://www.Leidinger.net Alexander @ Leidinger.net GPG fingerprint = C518 BC70 E67F 143F BE91 3365 79E2 9C60 B006 3FE7
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