I have written a stupid backup utility that copies new or modified files. That's fantastic until I come across files that are 11 GB in size that have been modified. I have a feeling I can compare the file to be backed up and the file that will be over-written (old version of file) and "synchronize" the file instead of copying the entire 11 GB. I am not sure how to start researching this, could anyone point me in the right direction?

