SCSI Termination DDS4 dat drive

Hi,

I'm having trouble with NT backup giving hardware errors whilst backing up onto Sony SDT-11000 drives.  3 units are displaying the same problem on different PC's.  At some point during the backup I get a reported hardware failure in the report log:-

Error: The device reported an error on a request to write data to media.
Error reported: Hardware failure.

I replaced the drive with a DDS3 unit and that over the period of a couple of weeks that worked OK so I guessed the software and SCSI controller appeared to be functioning correctly.

I then got a replacement DDS4 drive and then that started to display the same problems as before i.e. hardware errors during the backup.  My question is that the SCSI controller card came with a standard 68pin cable.  Am I incorrectly configured regarding the SCSI setup?  Should I be using a 68pin cable with a terminator at the end?  I didn't with the DDS3 and that seemed to work fine with the supplied cable mentioned above.  

Other thoughts are about if the compression dip switches need to be changed?  

I'm, clutching at straws as you might have guessed but I can't believe 3 brand new DAT drives would fail in this way.

Tried a number of new tapes too.

Any clues?
Thanks
Brendan
ellipticalAsked:
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cyrnelConnect With a Mentor Commented:
Brendan, termination could be the issue. If you don't have the drive configured to provide internal termination then by all means add it to the end of the chain. Those cables are transmission lines. Every connector, bend, flaw creates reflections. Card termination isn't enough, especially with long cabling. I've also seen problems with short cabling where reflections appeared with the right timing to be a valid signals, but error-creating ones. Differences between drives, even of the same model, can be enough that one fails and another works, and if borderline it can change over time in very mysterious ways that defeat attempts to troubleshoot. No way to know exactly what's going on without hooking up a scope and watching the signals so I try to be good about the rules. Enable auto-termination on the card and add one to the end of the chain. Of course, make sure all "non-end" devices have termination disabled.

Let us know how it goes.

GL,
Dave
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Cyber-DudeCommented:
Try the following:
http://support.microsoft.com/default.aspx?scid=kb;en-us;817688

(that is if you use Windows 2003)

Cyber
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ellipticalAuthor Commented:
No sorry no 2003!

Windows 2000 professional and Windows XP professional

Thanks
Brendan
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ellipticalAuthor Commented:
I should add the SCSI Controller is a Tekram 395-UW

http://www.tekram.com/ProductSpec.ASP?Product=DC-395

Thanks
Brendan
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Cyber-DudeConnect With a Mentor Commented:
Try to terminate the cables (though Im not so sure it is the origin of all your problems).
Heres an intresting thought... I wonder (I havent tried it before on non HP products) if you can use HP StorageWorks to diagnose the problem. It may report you referring a firmware update (though it may report you an unknown firmware version)... Give it a try:

The link:
http://h20000.www2.hp.com/bizsupport/TechSupport/DriverDownload.jsp?pnameOID=406731&locale=en_US&taskId=135&prodSeriesId=406729&prodTypeId=12169

Good luck

Cyber
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dovidmichelConnect With a Mentor Commented:
Yes a terminated cable is needed.

This has nothing to do with the need to have the tape drive terminated.

The contoller is Wide and the tape drive is Narrow. That means it is going from 68 to 50 pins and those extra lines need to be terminated, hence the terminated cable.

Also go into the configuration setup for the controller and disable Wide negotiation, and set the transfer speed down to 10, 20, or whatever the lowest setting is if it does not go down that low.

As for why the DDS 3 worked fine and the DDS 4 not, my best guess is the improved throughput in the 4 is enough to make it susceptible.
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cyrnelCommented:
All lines need to be terminated, not just the high-Byte from 68 to 50. It has very much to do with terminating at the tape drive if it's the end device. Otherwise terminate the cable or whatever device is at the end of the cable. Don't believe me? Connect a fast scope and record the signals with and without termination. Single ended can certainly work but the margin for error is muchly reduced. That's where most of the SCSI issues I've seen over the past 20yrs have begun. T's (stubs), extensions, bad cable, but most often sloppy termination.

I would agree however that dropping negotiated rates could improve the situation.

Dave
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dovidmichelCommented:
Cyrnel's update points out that my post was not clear, here is what I was trying to say in my second line.

The need to have a terminating cable when going from Wide to narrow does not negate the need to terminate the tape drive, both are needed.
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ellipticalAuthor Commented:
Update folks!

I tried a properly terminated cable (68 pin) and the scsi card was unable to detect the tape unit.  I then swapped the Tekram SCSI card for a spare adaptec 2940U2W which has the LVD connector.  I connected the same terminated cable and it detected the tape drive fine and initial backup tests look good.  My question is now why would the Tekram fail to see the tape drive with the terminated cable?  Is there a shortcoming on the controller in some way?

It may end up that I replace the SCSI controller at my other sites but I'd rather know that I'm not wasting my time doing that if in fact the Tekram could support the tape unit.  I do see that the Tekram does not have the LVD option.

Thanks
Brendan
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dovidmichelConnect With a Mentor Commented:
It could be that the Tekram card just might not be compatible with the drive. Some of them only support Wide and Ultra2 devices and the drive is neither. Also the Tekram card might only support thier own Wide to Ultra2 adapter and cable.
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cyrnelConnect With a Mentor Commented:
Yep, it could be the Tekram card is just less tolerant of whatever combination you're using. Sorry, but I haven't used one of their cards since UW was recent) An Adaptec LVD capable card will have a better chance of dealing with weird signal levels since it has to work in both SE and differential modes, and autosense between the two.

How long is the cable? How many pieces/extensions/etc? Just in case, list everything from backplane to end of cable.
What kind of terminator are you using? (active or passive? active often have an LED. It can be impossible to tell with cheap versions.)

I'm guessing cable length plus terminator is too much for the Tekram. If so an active terminator may help by terminating without dropping signal levels below the card's minimums. Try removing the terminator and test if the Tekram sees the drive. I'm not suggesting you run this way but it's a low bandwidth way to tell if signals are being pulled too low by termination. That would suggest you shorten/simplify the cabling and/or get a higher quality terminator.
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ellipticalAuthor Commented:
Hi chaps,

It appears to be consistently working now so thanks for the feedback.  The answer is as you've pointed out, always use a properly terminated cable and a properly supporting scsi card.  I was fooled by the fact that the Tekram and it's cable correctly identified the drive and on the surface appears to work on  some basic tests.  However when left for a full automated backup it showed it's true colours or lack of them!  

I'm going to split the points.

Thanks again.
Brendan
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