Quickly move to the end or beginning of big chunks of data.
There are a lot of ways of doing differential backups, tons of software, freeware of shareware. I want to share one I didn't know about which I liked very much. It is unfair so little information can be found the Net about 7-zip archival tool, which can handle differential backups with ease. Article is for CLI geeks, who understands where to push these commands )