More on tape drives

[James T Talley]

To add to the discussion on tape backup for A/UX systems, I have some
information and a question. Someone mentioned that they were
considering purchasing an FWB hammerTape because it at least claimed
to work with A/UX.  As someone that has used the hammerTape250 from
FWB for about a week with our A/UX system, I can verify that it seems
to function as advertised.  I've used pax, cpio, dd, and dump.bsd with
it and am able to reliably read and write the tape.  With one minor
exception (see below) I'm quite happy with it.  (If you want more
info, let me know.)

My question has to do with writing multiple files to a single archive
tape.  The FWB software lets you address the drive as '/dev/rmt/tc4'
or '/dev/rmt/tc4n' where 4 is the SCSI ID of the drive and the 'n'
means do *not* rewind when done reading or writing.  Thus the 'n'
version of the device lets you write multiple files to one tape
cartridge.

I'm using the '/dev/rmt/tc4n' device to archive large transient files
that arrive on my system each night via UUCP.  My problem is that it
seems that you have to make all the writes in one pass.  As long as I
only make writes to '/dev/rmt/tc4n' device, I can continue writing
files to a single cartridge.  As soon as I use the 'mt' command to
reposition the tape, I start to get write errors and can no longer
write more files at the end of the tape.  If I rewind and start over,
I can start making multiple writes again.

This means I can continue using the cartridge to store more data as
long as I don't try to access the data that's already on the tape.
Any other access seems to make it read-only until I rewind and re-use
the whole tape.  I can live with this, if necessary.

Is this normal?  Am I missing something obvious?  The man page for
'mt' is not very helpful in this regard.  Any help is appreciated.

James T. Talley