Messages in this thread | | | Date | Wed, 2 Jan 2002 19:41:50 +0100 | From | Vojtech Pavlik <> | Subject | Re: Two hdds on one channel - why so slow? |
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On Wed, Jan 02, 2002 at 06:21:25PM +0100, Krzysztof Oledzki wrote: > > > On Tue, 1 Jan 2002, Brian wrote: > > > This is an inherent quirk (SCSI folks would say brain damage) in IDE. > > > > Only one drive on an IDE chain may be accessed at once and only one > > request may go to that drive at a time. Therefore, the maximum you could > > hope for in that test is half speed on each. Throw in the overhead of > > continuously hopping between them and 12MB is no surprise. > > So?!? This ATA100 and ATA133 standards do not make any sens? It is not > possible to have more than 66 MB/sec with on drive and is seems that it is > not possible to use more than ~30MB/sek of 100 or 133 MB/sec ATA100/133 > bus speed with two HDDs. Oh :((( > > Another question - why ATA100/ATA66 HDDs are so slow with UDMA33? > With new IBM 60 GB IC35L060AVER07-0 I have much more than 33 MB/sec with > ATA100 and only 24 MB/sec with UDMA33 (Asus P2B with IntelBX). New 80GB Seagates > (Baracuda IV) have the same problem.
Actually 24 MB/sec is quite a miracle with UDMA33. I'd expect values around 16 MB/sec. Because, as far as I know, unlike SCSI, IDE doesn't do concurrent reads and transfers (except for readahead), effectively halving the interface transfer speed.
-- Vojtech Pavlik SuSE Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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