- what are the fundamental differences with NFS ? 

- One of the design goals of NFS was to make it easily portable across operating systems and file systems. NFS is also a virtualization independent solution.

- Third party developers and motivated administrators can use NFS servers for implementing / deploying third-party FSes

- FSVAs will have to deal with exactly the same set of issues that the much more mature NFS project is currently dealing with in terms of cross-version compatibility

- Given the existence of NFS and its many variants, the contributions of this work seem hard to fathom. At the very least the authors need to provide a more in-depth discussion of why using and extension of NFS is not sufficient. A straightforward extension would be using native inter-VM communication mechanisms (such as XenSockets).