I use Time Machine. In addition to the I backup stuff to external drives and store them offsite. The problem is how long it takes to do that. For example, I copy my iPhone library to the external drive, it's very large. Then 2 weeks later I bring back the external drive and delete the old iPhoto library, which takes a while, and then copy the entire new library over. Is there any other way to do it in which only the newer items would be added instead of having to delete the old version and copy over the entire new one?