Network File System (NFS) is a network file system protocol originally developed by Sun Micro systems in 1984, allowing a user on a client computer to access files over a network in a manner similar to how local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. The Network File System is an open standard defined in RFCs.
Original NFS version
The implementation details are defined in RFC 1094. Sun used version 1 only for in-house experimental purposes. When the development team added substantial changes to NFS version 1 and released it outside of Sun, they decided to release the new version as v2, so that version interoperation and RPC version fall back could be tested.
Version 2 of the protocol (defined in RFC 1094, March 1989) originally operated entirely over UDP. Its designers meant to keep the protocol stateless, with locking (for example) implemented outside of the core protocol. NFSv2 only allowed the first 2 GB of a file to be read.
Version 3 (RFC 1813, June 1995) added:
- support for 64-bit file sizes and offsets, to handle files larger than 2 gigabytes (GB)
- support for asynchronous writes on the server, to improve write performance
- additional file attributes in many replies, to avoid the need to re-fetch them
- a READDIRPLUS operation, to get file handles and attributes along with file names when scanning a directory
- assorted other improvements.
At the time of introduction of Version 3, vendor support for TCP as a transport-layer protocol began increasing. While several vendors had already added support for NFS Version 2 with TCP as a transport, Sun Micro systems added support for TCP as a transport for NFS at the same time it added support for Version 3. Using TCP as a transport made using NFS over a WAN more feasible.
Version 4 (RFC 3010, December 2000; revised in RFC 3530, April 2003), influenced by AFS and CIFS, includes performance improvements, mandates strong security, and introduces a stateful protocol. Version 4 became the first version developed with the Internet Engineering Task Force (IETF) after Sun Micro systems handed over the development of the NFS protocols.
NFS version 4 minor version 1 (NFSv4.1) has been approved by the IETF and received an RFC number 5661 since Jan 2010. The NFSv4.1 specification aims:
- To provide protocol support to take advantage of clustered server deployments including the ability to provide scalable parallel access to files distributed among multiple servers (pNFS extension).
- to provide sessions and Exacely One Semantic (EOS)