1M blocks and optionally write the read data to a file or disk.
If a read error happens, the 1M block gets put on the end of the worklist
and will be retried with 64k blocksize.
If a read error happens again, the 64k block gets put at the end of the
worklist and will be retried with single sector reads.
The program keeps trying until you stop it.
You can refresh a disk:
recoverdisk /dev/ad1 /dev/ad1
or salvage a floppy:
recoverdisk /dev/fd0 myfloppy.flp
