Playing with Fedora Core 4's prebuilt version,
seems to be 2.4.5p2.

I confirmed I could write to the tape by doing
a small tar and recovery.

I setup stinit to give me a non-compressing device,
/dev/nst0l with a fixed block size of 32KB.

Then, using the same tape I ran:

  amtapetype -b 32k -e 12g -f /dev/nst0l -t DDS-3-nocomp -c

to confirm my device was non-compressing.  Everything looked
good, so I recalled the command and edited off the trailing "-c"
and went to bed to let amtapetype run overnight.

Surprise, this message greeted me this morning with no results:

  amtapetype: The tape is already used, use -o to overwrite the tape

Uhh, yeah, I used it for a tar.  And you used it after that for
the "-c" check.  But you didn't complain for the -c check.

If the overwrite check is valuable, then it should also apply to
the hueristic check for compression setting ("-c") as that check
also destroys data on the tape.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
 4455 Province Line Road        (609) 252-0159
 Princeton, NJ  08540-4322      (609) 683-7220 (fax)