Messages in this thread | | | Date | Wed, 2 Jan 2002 11:31:40 -0800 (PST) | From | Andre Hedrick <> | Subject | Re: Two hdds on one channel - why so slow? |
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Brian,
This was true in the past and with many older drivers. However when and if the new driver I have is adpoted, it will make SCSI cry. So please stop polluting the issue.
Let me be as objective as I can be.
I built a special Mylex 3-channel raid 10 systems using 6 15K drive at Ultra160. Given that I was clever, I was able to push that system to read and write at 170MB/sec. I was very impressed by this performance, however this was hardware raid, caching of 256MB, and 66/64 pci bus. This was a dual PIII w/ 2GB of EEC-Buffered-Registered.
Now I have managed to use two hosts w/ 4 channels no caching controller, no hardware raid, 4 7200RPM drives and software raid 0. I was able to push 109MB/sec writing and 167MB/sec reading.
Also under a similar environment, I was able to, using a single card, 4 drives, not hardware-raid, no caching controller, reach 90MB/sec writing and reading was about 78MB/sec.
Now lets adjust cost of componets and SCSI loses big. Once there are 10K ATA drives in the market, and none exist that I know of to date even in beta, then we can retest .
In the meantime here is another dose of reality.
http://www.tecchannel.de/hardware/817/index.html
Regards,
Andre Hedrick Linux ATA Development
On Wed, 2 Jan 2002, 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. > > Best regards, > > Krzysztof Oledzki > > - > 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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