DAT tape drive strangeness

[Marty Metras]

I have a couple HP C2954D external tape drives.
ioscan says that they are HP35480A inside.
I am trying to use one of these and when I insert some to the tapes it just reject them.
Some of them work just fine and others when I put them in the drive they seam like the are going to work but after a few seconds they eject.
I have tryed new and used tapes. I have tryed 60M, 90M and 120M. Digitial, HP, Maxell, and Fukifilm. New and old alike. Oh DDS, and DDS1,2,3.
And I have replaced the Drive once.
When the tape stays in the drive it works fine.
Am I missing some thing here?

Marty

[A. Clay Stephenson]

I suspect you are using tapes with and without "Media Recognition System" and that is accounting for the differences in behavior. Generally there is a DIP switch to enable/disable MRS.

You could also be seeing old hung processes so that as soon as a tape is available, it tries to rewind and eject the media. To eliminate that possibility, I would disconnect the tape drive from the host and see if the media then behaves itself. If the problem arise only when connected to the host then I would tend to suspect faulty termination. Bad/missing termination can cause a drive to almost work perfectly -- the worst kind of problem. Look for termination enabled on the drive itself and an external terminator -- this would be bad.

[Bill Hassell · Accepted solution]

The 35480A is a DDS-1 drive, very old and cannot use ANY tape longer than 90 meters. It will accept 60 meter tapes but make sure that these tapes are not marked DAT--they must be marked DDS. 90 meter tapes are also DDS tapes. There is no backward compatibility with the longer tapes as not only the length is different, but the recording method is incompatible. The 35480A is the least compatible DDS drive there is since it is so old. The tape reject should never be defeated as putting a DDS3 or DDS4 tape into the drive mayy cause the tape to tangle and this almost always requires a replacement of the entire drive. The drive is only letting you use tapes that are compatible.

[Marty Metras]

Thanks Bill that was the issue.
I didn't know that there was differences in DAT/DDS tapes.
When we replaced the 2 servers a couple years ago we had no need to have a DAT drive.
Well, someof our Apps updates come on DAT tables and I can't get all of them to to use CD, DVD, or DLT so I broke down and bought a couple cheep DAT drives.
I always read/write and DAT/DDS the tapes at home with the old junk I use at home. Never gave it a thought about tape being different.
Well I know now. And you get what you pay for.
Thanks you for taining me again.
Marty

[Bill Hassell]

Actually, DDS isn't the only tape format with different (and incompatible) versions. DLT, AIT, Ultrium, all have bigger and better tape capacities, but the technology is very different (not just thinner and longer tapes).

If you've ever inserted a 120 minute cassette tape into a car stereo, you probably discovered that longer tapes are not always compatible (as you try to unwrap the tape from the mechanism). New tape drives can cost 2 to 10 thousand dollars and if the drives did not protect themselves, there would be a lot of drive repairs and unhappy customers.