SUMMARY: dump parameters for exe-8505xl?

From: Yuan Lu (
Date: Tue May 02 1995 - 07:01:51 CDT

Hi managers,

Sorry for the delay. I was distracted for some other things.

My original question is how to specify the b,d,s parameters when
using dump command for EXE-8505XL tape dive with 160m EXB tape.
Several people replied my request. Some have sent their commands
to me. Thanks to all kind souls. Here are the summary:

Most people agreed that the block factor should be 126, the density
should be 54000 and the size of the volume should be 13000*FACT, where
FACT=160/112~=1.4 .

There are two replies which gave me very different values. So I called
R Squred. The answer is that I should put the "biggest number I can
think of for the size of the volumes. If the end of tape is detacted,
the program will abort automatically." Obviously, the size of the volume
is pretty much made-up as several people already pointed out.

The command I used is:

dump 0ucbdsf 126 54000 80000 /dev/nrst17 FILE_SYSTEM

where device name /dev/nrst17 is for 8500 format with compression.

There is one thing abort compression, though. I can only backup about 8.3GB
data using 160m tape and 6.5GB using 112m tape, which are far lower
than the expected capacity. I got "tape write error" and "fopen on
/dev/tty fails" messages at the end of the dump. The technical support
person at R squared said that the messages did indicated the end of
the tape because they did the experiment as I requested and got the
similar error messages. As to the capacity, it is probably because my
data are already compacted. Hope this will give you some hints when you
try to compact too much data into one tape.

Again, thanks all who replied.

Yuan Lu

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