A system for backing up data files generates information from which those files can be recovered, and it sends that information to a back-up location. To determine what information to send, it generates summaries of those files from time to time and identifies changed locations by comparing the summaries...http://www.google.es/patents/US7225208?utm_source=gb-gplus-sharePatente US7225208 - Systems and methods for backing up data files
