[Info-vax] Odd tape drive behavior

[Stephen Hoffman]

On 2013-12-04 20:43:12 +0000, tadamsmar said:

> I bought a cheap used WangDAT 3900 tape drive of ebay.

In the best of times, DDS/DAT is write-once read-maybe media format.  
Even when those do devices work, they still scrape off oxide.  My 
personal best record with those was one week of daily backups on a 
cartridge, before the cartridge was trash and the heads needed 
cleaning.  That was with multiple not-cheap vendors of brand-name 
cartridges, and regular cleaning passes.  Official spec for most DDS 
was ~1000 head passes, and whether I hit that on the shoe-shining that 
VMS normally does with the tape header blocks during MOUNT and BACKUP 
and related, or if the head pass specs were just optimistic, I never 
bothered to determine.

FWIW, The SRM console drivers know how to ask a SCSI device its name, 
and not much more.   The VMS drivers actually try to use the device.

Most magnetic tapes are compatible at a basic operational level, so it 
would appear this drive is either bad, or the command interface is 
incompatible.

A cheap DLT/SDLT/Ultrium tape drive would be a more likely to work, and 
work reliably.  Barring bad cartridges and bad drives, some of which 
are around.

Personally, I wouldn't touch DDS with a barge pole.


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