I'd like to thank everyone who helped me with this problem. It
has finally been resolved. 

I'm sure people are curious as to what happened (I know I would
be), so here goes:

After my last round of suggestions from people, I tried them
all, but still with no success. I was talking with another tech
friend who suggested that it sounded like it could be a firmware
problem with the drive and that I try updating that. The tape
drive was from IBM, so I went to the dowloads page for this unit
and downloaded two .exe files that both created a bootable
floppy disk (there was two as they were for two slightly
different DDS4 tape drives). I tried both of the boot floppies
and both of them tried to run the firmware update and both
failed with the error "no supported drives found to update".
This was despite the fact that I could see the tape unit in the
list of drives detected. At this point I placed a service call
with IBM, as I was getting really frustrated and it was looking
more like a hardware problem (hey, if their firware updater
can't find the drive, what hope do I have !). The tech who came
out was really good and even though he had absolutely no Linux
knowledge, he watched what happened when I tried to label a
tape, etc. He suggested maybe SCSI cable and went and got a
spare from his car, no good. He then called someone else and had
a chat to them and they asked what it was connected to. Well it
transpires that as I was using a "non-supported" SCSI controller
to do my testing (I was using a standard Adaptec AHA-2940) they
wouldn't support it. The tech guy was quite helpful though, he
swapped the DDS4 tape drive, gave me a brand new one and told me
to connect it back to the IBM server (with the "supported" SCSI
card) and see how it went. If I was still having problems, call
him back.

So last night, I put the tape drive back into the server and
scheduled a backup and IT WORKED !

I am now left wondering if the tape drive was faulty (it was
replaced) or if it was something screwy with it not working on
the two seperate SCSI controllers I tried it on outside of the
server.

Thanks again everyone and I did gain one thing from the
exercise, I worked out how to disable compression on my tapes,
so I should now get the full 20GB per tape.


regards,
Tony.


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