"Blank check" media error on Tru64?

[BTamás_1]

Configuration:
AlphaGS1280 fw 7.2a
Tru64 UNIX 5.1B-4
KGPSA-EA highest fw (with 7.2a CD upg)
FC switch 2/16 EL(Brocade silkworm 2400)3.1.3a
NSR M2402 Network Storage Router fw:5.6.7a
SDLT 160/320 TT fw:v95

When we make a backup to a new media (don't mind HP or Fuji brand), generally (approx: once or

twice to success) we get a vdump error message early in vdump(command is for example: vdump -0f

/dev/ntape/tape0c /var):
"vdump: unable to write to device ; [5] I/O error"
- then the media seems to be "blank" by "mt status"

When we make a backup to used media, we never get error message at the beginning of the tape.
Are there any similar experiences somewhere?
Can somebody help and/or explain the symptom me?

Thanks in advance
Tom

[Vladimir Fabecic · Accepted solution]

Do you get the same error if you use "/dev/ntape/tape0_d1" instead of "/dev/ntape/tape0"?

[BTamás_1]

Thanks Vladimir, this is a good idea (that tape0c is not an "exact" device), we will try vdump it to tape0_d1. We always make our vdump-s to the device /dev/ntape/tape0c.
I will report about suggested vdump.
Tom