Defragment the specified device rather than a file.

    The model used is based on a 4-pass strategy:

    o  Pass 1: for any non-contiguous files, attempt to defragment
       them into existing exactly sized free space (in other words,
       for a 500 block file, look for a 500 block free space).

    o  Pass 2: for any non-contiguous files, attempt to defragment
       them into a 'best fit' block of free space.

    o  Pass 3: consolidate free space by moving files out of the
       largest block of free space into other matching free space
       blocks.

    o  Pass 4: consolidate free space by moving files out of the
       largest block of free space into a 'best fit' block of free
       space.