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Poor Disk Performance Again

Ayman Altounji
Valued Contributor

Poor Disk Performance Again

I have been doing some more tests on physical write/bytes per sec on the ML370 and get an average of just over 3Mb/sec copying a 1.3Gb raw data file. Or 7.2 Minutes to copy. Supposing that we should be running at 160Mb/sec (The 431 is U3 as are the drives) then in theory we should expect 160Mb/sec on burst, say for argument's sake that averages out to 50% which gives us 80Mb/sec. As we are running Raid 5 and don't have any write cache, shall we deduct another 50%? This then gives us 40Mb/sec. So at 40Mb/sec that should copy our file in 35 seconds. It currently takes 10 times as long. I understand your argument regarding the write cache, but can it have this much of a detrimental effect?

Incidentally, with the same file on the 1600R (mirrored), I get approx 5Mb/sec. (again way below Ultra2 scsi performance) - the same file on my laptop (PIII 700, 20Gb IDE) I get 3Mb/sec !

Also - I have now upgraded the internal SCSI cable to part # 166389-B21 - The recommended cable to get U3 performance;
I have now noted that this has not improved performance at all.

I am now going to try an SA5302 to see what happens.

Can you point me to any benchmark tests and performance figures re disk i/o & DTR's etc as I can't find any on the Compaq site? This would be most helpful.

Many thanks

Ayman Altounji
Valued Contributor

Re: Poor Disk Performance Again