the size of each block (in bytes) written on the media.
If the files to back up are small,
set the block size to a smaller value.
If you set the block size to a larger value,
the access time is less efficient.
the capacity of the media (in KB).
For example, a cartridge tape might be capable of storing
60MB (60000KB), 150MB (150000KB), or 520MB (520000 KB).
Do not change the default volume sizes for floppy drives.