5) rerun the tapetype and get the true capacity of the tape so
you can update that entry in your amanda.conf.  It should go up
a bit because tapetype uses /dev/urandom as the data source for
its test writes, and the data from /dev/urandom is so random
that it overpowers the hardware compression and actually grows
to be larger on the tape than what tapetype seems to think it

is.

Here is the newly generated conf generated by tapetype program:
define tapetype unknown-tapetype {
  comment "just produced by tapetype program"
  length 3916 mbytes
  filemark 174 kbytes
  speed 446 kps

Previously, it was:
define tapetype C1533A_120 {
  comment "HP C1533A DDS2 with 120m tapes"
  length 3858 mbytes
  filemark 107 kbytes
  speed 507 kbytes