rdiff-backup keeps an entire (uncompressed) copy of the files you are backing up, and it also keeps a history (incremental backups), so this means that your backup space needs to be larger than what you're backing up. if you are backing up 100 gigs of space, you may need 120 gigs of space (on a separate hard drive preferably!).

This is all lower case. Can you fix that?
rdiff-backup keeps an entire (uncompressed) copy of the files you are backing up, and it also keeps a history (incremental backups), so this means that your backup space needs to be larger than what you're backing up. If you are backing up 100 gigs of space, you may need 120 gigs of space (on a separate hard drive preferably!).