Copy disk content to second disk.

Make a back up copy of your disk space.

1. Make a copy of first disk to the second disk. Lets assume first disk is /dev/sda and the second disk is /dev/sdb.
# dd if=/dev/sda of=/dev/sdb
where, if --> input file; of --> output file.

or

# dd if=/dev/sda of=/dev/sdb conv=noerror,sync

the above command will continue runs even you get error..

Note: Make sure to pick right source disk and destination disk. You may loose imp data.