Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1983, allowing a user on a client computer to access files over a network as easily as if the network devices were attached to its local disks. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. The Network File System protocol is specified in RFC 1094, RFC 1813, and RFC 3530 (which obsoletes RFC 3010).
Parallel NFS (pNFS) is an extension to NFS v4 that allows clients to access storage devices directly and in parallel thus eliminating the scalability and performance issues associated with NFS servers in deployment today. This is achieved by the separation of data and metadata, and moving the metadata server out of the data path as shown in the diagram below.
Note that pNFS supports the use of 3 storage protocols in the data path – blocks, objects and files.