Writing to 1/2" 9-track tapes under Sun OS

[Douglas Harvey]

I have a question on the amount of data that can be written to a standard
1/2" 9-track tape from a Sun workstation.  We are using Sun 4/280's and
some SPARCstations running v4.01.

Tapes we receive from clients typically hold between 150-160MB on them.
Most of these tapes are created on IBM mainframe systems.  For example,
assuming the block size was 32718, we would do:

	dd if=/dev/nrmt8 of=header bs=80   (grabs tape header)
	dd if=/dev/nrmt8 of=data.fil bs=32718 (data file)

Now if we try to use the same block size (32718), we can only manage to
put 140MB back on the tape.  This is puzzling since we didn't have any
trouble reading the data off the tape.

Does anyone know why this might be?  Any help would be appreciated.

Thanks in advance,

Douglas Harvey                      Email: drharvey at chinet.UUCP
Hewitt Associates                   Compuserve: 72341,104
100 Half Day Road                   Phone: (708) 295-5000
Lincolnshire, IL  60069