Date: Tue, 8 Apr 2003 19:25:55 +0200 From: Wilko Bulte <wkb@freebie.xs4all.nl> 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: <20030408172555.GA9572@freebie.xs4all.nl> In-Reply-To: <xzpof3gnc6f.fsf@flood.ping.uio.no> References: <Pine.BSF.4.21.0304081001400.27414-100000@root.org> <xzpof3gnc6f.fsf@flood.ping.uio.no>
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On Tue, Apr 08, 2003 at 07:15:04PM +0200, Dag-Erling Smorgrav wrote: > Nate Lawson <nate@root.org> writes: > > Tagged queuing is orthogonal to caching. TQ allows multiple transactions > > to be passed to the drive, allowing it to order and aggregate the requests > > as it thinks best. TQ can be done with no cache because all the drive is > > tracking is handles to transactions (typically 16 bit ids). Think of it > > as more like a pipeline than a cache. > > It can't be done without cache, because you can't queue and reorder > transactions without some sort of cache. But you could do read buffering (to avoid the C word) only, so no write cache which has the volatility issues which have been discussed over and over again in combination with ATA drives. I still don't get it why ATA drives cannot be built to the same spec as SCSI drives as far as write caching etc are concerned Probably cost ;) ATA is for el-cheapo stuff. Serial ATA might see new uses, say in arrays. W/ -- | / o / /_ _ wilko@FreeBSD.org |/|/ / / /( (_) Bulte
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