Our Quantum 4000 cannot read DLT IV tapes that were backed-up on our Quantum 7000 tape library

[Michael C. Kluytman]

Our Quantum 4000 tape library cannot read DLT IV tapes that were backed-up on our Quantum 7000 tape library. Is there any way to work around this? The tapes are read and writable in the reverse order. We have even tried quick-erasing the tape on the 4000 first-then backing up a file on the 7000 and then trying to restore back to the 4000-no luck. We have been told you cannot change the density on the 7000 to match the 4000. Any suggestions?

[A. Clay Stephenson]

Sorry, that dog won't hunt. Tapes written by a 4000 are readable by a 7000 or 8000 but the converse is not true. The density and compression are beyond the ability of a DLT4000. Even writing to a 7000/8000 uncompressed won't help you.

I can give you a possible plan B if the two hosts are close enough that you do not exceed the maximum bus length of 25m for HVD SCSI. You could attach the DLT7000 to both hosts.

HostA (SCSI ID 7) --- DLT7000 (SCSI ID 2) ---- DLT4000 (SCSI ID 3) ---- HostB (SCSI ID 6).

The terminators must be enabled on both controllers and you MUST set the SCSI ID of one of the controllers to 6. In this example, I attached both drives to the same bus and this works fine as long as only one drive is active at any given time. The DLT7000/8000 requires a dedicated bus so that if you try to use both drives the 7000 willl be starved for data. I actually use configurations like this so that either host can read/write to either drive and it works quite well.

Regards, Clay

[Michael Tully · Accepted solution]

Hi,

The DLT 4000 is not backwards compatible
to either the 7000 or 8000. Other than
what Clay has already suggested which
may not be feasible as if I've read
this right you tape libraries, you
could try to write the data on the 7000
and 8000 in 4000 format. This would not
be the best idea as you would lose the
ability to write the same amount of data.
Have a look at the below posting on how
to set up devices for lower formats.

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x4381abe92dabd5118ff10090279cd0f9,00.html

-Michael

[Michael C. Kluytman]

Thanks for the quick replies! Since the two tape libraries are in two different cities, and the need to restore from the 7000 to the 4000 is a one-time deal, Michael's solution of writing the data in a 4000 format on the 7000 machine sounds like our only possible solution. Our problem has been HOW to create that format on the 7000. We will try the patch and post the results...