amanda@buka:~$ amtapetype -o -e 20g -t DDS-4
Writing 256 Mbyte   compresseable data:  27 sec
Writing 256 Mbyte uncompresseable data:  101 sec
WARNING: Tape drive has hardware compression enabled
Estimated time to write 2 * 20480 Mbyte: 16160 sec = 4 h 29 min
wrote 524240 32Kb blocks in 80 files in 6612 seconds (short write)
wrote 524160 32Kb blocks in 160 files in 6755 seconds (short write)
define tapetype DDS-4 {
    comment "just produced by tapetype prog (hardware compression on)"
    length 16385 mbytes
    filemark 32 kbytes
    speed 2510 kps
}