DLT 7000 speed & capacity

[Jorge E. Prada]

I have DLT 7000 tapes with 35/70 GB capacity.
the average speed of the tape library is 6 MBPS.
1.- Some times the tape drive loads a tape and the speed drops to 400 KBPS or even 95 KBPS.and the back up slow down so much that I have to stop it. I change tapes and the speed is now 5 or 6 MBPS.
2.- Some times the tape is maked full with only 15 or 20 GB of data.
So the question here is: How can I know or test the status of the tape to make sure that it is in good condition ?
How is that a tape can slow down the back up speed from MB to KB ?
Thanks

[Eugeny Brychkov]

Jorge,
1. download and install HP LTT from http://www.hp.com/cposupport/information_storage/support_doc/lpg50128.html . Play with it checking your drive. There is a perfomance test. Please check drive's firmware to be the latest;
2. a) If you're backing up compressed files with hardware compression than there will be data overhead so you'll get even less than 35GB; b) you have bad tapes with bad blocks;
Please generate LTT support ticket and attach to your next reply
Eugeny