salas@pprg.unm.edu (NN]) (01/24/89)
Hello all,
We in the ECE department at UNM have run into an interesting
problem with dump (8) and TK70's. Here is the situation:
We have several VAX stations (two 3500's and a 3600) running
Ultrix-32 V3.0 (Rev 64) and have been using dump to back them up to
TK70. The tape is rated at 296 MB at high density, but we were not
able to fit more than 160MB. And in some cases could only fit 70MB.
We used the following command:
dump 0unf /dev/rmt0h /research
I understand that the tape drive is a streaming tape drive and that
the amount that can be put an a tape depends on the load on the system,
but this seemed quite rediculous. Under beta 3.0 we could fit more
on the tape, so we started to investigate.
dump was reporting the right density 10240, but the wrong size.
When we told dump that it had a 600 foot tape (the actual footage), we
got less than when we told it had a 1200 feet. This meant that dump
was asking for a new tape before all the tape was used. So we fooled
dump and told it that it was dumping to a 20000 foot tape using the
following command:
dump 0usnf 20000 /dev/rmt0h /research
This worked great, we were know able to put a 190MB partition on one
tape (220 MB with overhead).
I do not understand how the TK70 is setup, does anyone know:
How many tracks does it have? Is my analysis of it being a streaming
tape drive correct? In addition, why is fast forwarding so slow? It
takes longer to fast forward than it does to dump to the tape.
Some more trivia:
In our investigation we looked at the operator backup scripts in
/opr and they have the same problem. In addition, the multiple filing
system dump could be setup better. It only puts one filing system on
the tape instead of multiple filing systems on a tape. To do the later,
you will need to insert the following command in either dobackup or
backup:
mt -f /dev/nrmt0h fsf X
where, X is the number of filing systems. It seems a waste of tape
to have only one filing system per tape and at $45 per tape it is
also quite expensive.
I hope this information helps.
John Salas