Method and apparatus for efficiently backing up files using multiple computer systems

A system and method backs up computer files to backup drives connected to multiple computer systems. Each file in a backup set is allocated to one or more backup subsets for each of the multiple computer systems. The files can be allocated in an even number across each subset, allocated to evenly spread the number of bytes to each subset, or, using the capacity of each of the multiple computer systems, allocated so that each computer system can complete backing up the files allocated to it in approximately the same amount of time. The system can restrict the number of bytes continuously required from a single disk by one of the backup machines from exceeding a threshold limit. Each of the multiple computer systems is then directed to, and the computer systems do, back up files in one or more subsets, which may be allocated to that computer system.