ROW-FS: A User-Level Virtualized Redirect-on-Write Distributed File System for Wide Area Applications

The authors propose a virtualization approach to implement redirect-on-write capabilities that overlay a traditional distributed file system. The Redirect-On Write distributed File System (ROW-FS) is implemented via a user-level proxy that is able to selectively steer Network File System (NFS) RPC calls to one of two servers: a "Main" read-only server, and a "Shadow" read-write server. By employing virtualization by means of a user-level proxy and using the de-facto standard NFS protocol, ROW-FS can be mounted as an NFS file system by existing, unmodified clients from a variety of platforms, and requires no changes to existing kernels. Its primary application is in supporting wide-area computing environments, where ROW-FS can provide improved performance and fault-tolerance (file system modifications can be check-pointed along with application state).