Wierd performance loss for SCSI U320 drive

Hi, I have a Seagate ST336607LW scsi disc in my system, its only 34GB big and was intended to be used as the system drive.

I'm experiencing performance loss in a very wierd situation; Copying large files, say a cd image or a movie, and where the scsi disc is both the source and destination I get speeds of about 3-5Mb/s whereas I use any other drive in my system as either the source or destination I get between 30-70Mb/s depending on which drive I use.

I'm using an adaptec 19160 card with this drive, and I've checked and rechecked bios on card and the jumpers on the drive and the termination also so the drive should operate in its fastest mode. And it does except for the situation above. Very annoying. Using it as a system drive is not an option now. Could this still be a termination quality problem or some bus mastering issue?

Please help!

Another thing, which might be a clue, with the file manager I use (Dopus) I am able to pause a copy operation of a large file and after doing so and then resuming the copy I get a brief burst of speed up to where it is supposed to be, but then suddenly it drops again down to 5Mb/s. Seems to me like its a buffer overflow problem. Oh btw, I talked to seagate support, had the drive replaced but the problem persists even with the new drive.

(Also updated my ASPI drives to the latest I found)

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  1. Actually that sounds normal with my experiances.

    did you used to get good performance when copying to and from the same drive? If so --- what changed?

    Ive always found that using the same drive for source and destination for copying large files is quite slow. but when copying from 1 drive to another. scsi->scsi or ide->scsi its MUCH faster. this with u160 and u320 scsi drives.

    Have you run any benchmarks on the drive to see what its speeds are supposed to be at?
  2. 5Mb/s is not normal. I get alot better performance with my old ATA/66 drive in the same situation. There is something wrong definately, the drive makes alot of noise when this performance loss occurs and not in any other case.
  3. won't hurt to check termination. Bad termination can cause noise in cable, slowing down peformance.
  4. Could be that dopus has some bad code since this dramatic drop only occurs with pausing transfer and restarting using a non MS explorer...
  5. It's not Dopus I assure you (It was the first thing I tried) it happens with Explorer as well. The dramatic performance drop happens however I do it, from dos, opus, ms explorer etc.

    As for termination, I have a good quality cable (atleast I think, cost around 70euros) and the termination has three LEDs on it for PW (PoWer), LVD (Low Voltage Diff) and SE (cant remember this one). Both PW and LVD are on, and SE is not. Even so, is there really such a big difference in quality between cables from different manufacturers?
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