DFS Replication
Early versions of DFS used Microsoft's File Replication Service (FRS) which provides basic file replication capability between servers. FRS identifies changed or new files, and copies the latest version of the entire file to all servers.
Windows Server 2003 R2 introduced "DFS Replication" (DFSR) which improves on FRS by only copying those parts of files which have changed (remote differential compression), by using data compression to reduce network traffic, and by allowing administrators flexible configuration options for limiting network traffic with a customizable schedule.
Read more about this topic: Distributed File System (Microsoft)