Like floppy disks, there are two steps in the preparation of new tapes:
People with floppy tape drives need to do both. At present, there is no program available to low level format a tape, and thus, you will have to rely on DOS/WIN/OS-2 programs to do so. If you are planning on using taper, then you do not need to worry about step 2, since taper will take care of that for you. If you are not going to be using taper on that particular tape, then you will need to do a mt erase. Note that if you buy pre-formatted tapes (which I'd STRONGLY recommend since formatting can take 2-3 hours), then you by-pass step 1 ONLY - you still have to prepare the tape for Linux.
People with SCSI drives (esp DAT) may not need to format tapes for use under Linux. See your tape drive documentation for details. Similarly, you may not need to do step 2. Those drives that do not require step 2 may still require some information to be written on the tape before they will work correctly under taper, therefore, run mktape from the utilties menu before running tape. You can use the test make tape option from the utilities menu to see if your tape drive needs to have mktape run on new tapes. It is important that you put a brand new tape in the tape drive when testing.
STOP PRESS: The new ftape drivers (versions greater than or equal to 3.03) do not require tapes to be erased, however, the older ones do. Therefore, if you use the new ftape driver, you can set this preference OFF.
In addition, the new ftape driver can format tapes but it still takes time - save yourself a headache - buy preformatted tapes.
--erase-tape-off to tell taper that your tape doesn't need erasing. This is the default behaviour if you have started taper with --tape-type scsi.