A. The Distributed File System Namespace (DFSN) has been around since Windows NT 4 as a method to create an abstracted, logical namespace of selected shared file resources. It lets users see a single namespace of all file shares without having to know where the file shares physically exist and enables the logical view to map to multiple targets for each file share link. Users can automatically connect to copies of data that are physically closest to them based on Active Directory site.
The idea of having multiple targets for a DFS link is great, but the problem was keeping the multiple copies synchronized. Prior to Windows Server 2003 R2, the File Replication Service (FRS) was used, which was really not suited to the replication of large amounts of data. (You could also use a third-party technology, which could be costly or require a lot of effort to implement.) Windows 2003 R2 introduced the Distributed File System Replication (DFSR) service which offered a true replication technology that performed delta level replication (meaning only changes to files are replicated instead of the entire file). DFSR replication can be automatically enabled when creating DFSN link replicas. However, sometimes you might want to use DFSR for its powerful replication without using DFSN. This is completely supported and many organizations use DFSR outside of DFS-N. See "How do I create a new DFSR replica set?" for details on creating a DFSR replica outside of DFSN.