Parallel NFS (pNFS) extends NFSv4 to allow clients to directly access file data on the storage used by the NFSv4 server. This ability to bypass the server for data access can increase both performance and parallelism, but requires additional client functionality for data access, some of which is dependent on the class of storage used. The main pNFS operations draft specifies storage-class-independent extensions to NFS; this draft specifies the additional extensions (primarily data structures) for use of pNFS with block and volume based storage.