Hi,
Here is my understanding of the compatibility issues.
With the Quantum range of DLT's (2000, 2000XT, 4000, 7000 & 8000) there is
complete read & write backward compatibility.
Any drive will read its native capacity and any lower capacity without
problem.
On write if you are appending to a tape with existing data on it
the drive will write at the density already on the tape.
If you are writing at BOM (irrespective of any pre-existing data on the
tape) the default is the native density of the tape but this can be
changed to be any lower density by a command from the host, or using the
front panel controls of the drive after loading the tape.
On Tru64 there is a mapping (defined in ddr.dbase??) between the
write density and the device name. ie /dev/ntape/tape0 will be the
default density of your drive but /dev/ntape/tape0l could be fixed at
DLT4000 density.
There is a new breed of lower cost DLT drives recently introduced that
have 40/80Gbyte capacity on type IV tapes (I think that they are called
Benchmark DLT1) that have limited backward capacity. They can read DLT4000
tapes but have no write compatibility and tapes previously written to in a
DLT4000 need bulk erasing before they be used for write in a DLT1. They
also only have a 1.5Mbyte/sec transfer rate compared with 6Mbytes/sec of a
Quantum DLT8000.
I think that David McCall must have one of these drives.
I have seen a pointer to a company offering a bulk erase service. I can
probably find it again if anyone needs it.
Cheers
Tim Janes.
