Network File System - AbsoluteAstronomy.com

Network File System is a network file system

Network File System

Network File System is a network file system protocol originally developed by Sun Microsystems 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...

protocol originally developed by Sun Microsystems

Sun Microsystems

Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...

in 1984, allowing a user on a client computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

to access files over a network

Computer network

A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

in a manner similar to how local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call

Open Network Computing Remote Procedure Call

Open Network Computing Remote Procedure Call is a widely deployed remote procedure call system. ONC was originally developed by Sun Microsystems as part of their Network File System project, and is sometimes referred to as Sun ONC or Sun RPC...

(ONC RPC) system. The Network File System is an open standard defined in RFC

Request for Comments

In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...

s, allowing anyone to implement the protocol.

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 fallback could be tested.

NFSv2

Version 2 of the protocol (defined in RFC 1094, March 1989) originally operated entirely over UDP

User Datagram Protocol

The User Datagram Protocol is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol network without requiring...

. Its designers meant to keep the protocol stateless

Stateless server

In computing, a stateless protocol is a communications protocol that treats each request as an independent transaction that is unrelated to any previous request so that the communication consists of independent pairs of requests and responses...

, with locking (for example) implemented outside of the core protocol. People involved in the creation of NFS version 2 include Rusty Sandberg, Bob Lyon, Bill Joy

Bill Joy

William Nelson Joy , commonly known as Bill Joy, is an American computer scientist. Joy co-founded Sun Microsystems in 1982 along with Vinod Khosla, Scott McNealy and Andy Bechtolsheim, and served as chief scientist at the company until 2003...

, and Steve Kleiman.

NFSv2 only allowed the first 2 GB of a file to be read.

NFSv3

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

Transmission Control Protocol

The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...

as a transport-layer

Transport layer

In computer networking, the transport layer or layer 4 provides end-to-end communication services for applications within a layered architecture of network components and protocols...

protocol began increasing. While several vendors had already added support for NFS Version 2 with TCP as a transport, Sun Microsystems 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

Wide area network

A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...

more feasible.

NFSv4

Version 4 (RFC 3010, December 2000; revised in RFC 3530, April 2003), influenced by AFS

Andrew file system

The Andrew File System is a distributed networked file system which uses a set of trusted servers to present a homogeneous, location-transparent file name space to all the client workstations. It was developed by Carnegie Mellon University as part of the Andrew Project. It is named after Andrew...

and CIFS, includes performance improvements, mandates strong security, and introduces a stateful

State (computer science)

In computer science and automata theory, a state is a unique configuration of information in a program or machine. It is a concept that occasionally extends into some forms of systems programming such as lexers and parsers....

protocol. Version 4 became the first version developed with the Internet Engineering Task Force (IETF) after Sun Microsystems

Sun Microsystems

Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...

handed over the development of the NFS protocols.

NFS version 4.1 (RFC 5661, January 2010) 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).

Other extensions

WebNFS

WebNFS is an extension to the NFS file system for allowing clients to access a file system over the internet using a simplified, firewall-friendly protocol....

, an extension to Version 2 and Version 3, allows NFS to integrate more easily into Web-browsers and to enable operation through firewalls. In 2007, Sun Microsystems open-sourced their client-side WebNFS implementation.

Various side-band protocols have become associated with NFS, including:

The byte-range advisory Network Lock Manager (NLM) protocol (added to support UNIX System V
UNIX System V
Unix System V, commonly abbreviated SysV , is one of the first commercial versions of the Unix operating system. It was originally developed by American Telephone & Telegraph and first released in 1983. Four major versions of System V were released, termed Releases 1, 2, 3 and 4...

file-locking APIs).
The remote quota reporting (RQUOTAD) protocol (to allow NFS users to view their data-storage quotas on NFS servers).

NFS over RDMA is an adaptation of NFS that uses RDMA as a transport.

Platforms

NFS is often used with Unix

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

operating systems (such as Solaris, AIX and HP-UX

HP-UX

HP-UX is Hewlett-Packard's proprietary implementation of the Unix operating system, based on UNIX System V and first released in 1984...

) and Unix-like

Unix-like

A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....

operating systems (such as Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

and FreeBSD

FreeBSD

FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...

). It is also available to operating systems such as the classic Mac OS

Mac OS

Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...

, OpenVMS

OpenVMS

OpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is a computer server operating system that runs on VAX, Alpha and Itanium-based families of computers. Contrary to what its name suggests, OpenVMS is not open source software; however, the source listings are available for purchase...

, Microsoft Windows

Microsoft Windows

Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

, Novell NetWare

Novell NetWare

NetWare is a network operating system developed by Novell, Inc. It initially used cooperative multitasking to run various services on a personal computer, with network protocols based on the archetypal Xerox Network Systems stack....

, and IBM AS/400. Alternative remote file access protocols include the Server Message Block

Server Message Block

In computer networking, Server Message Block , also known as Common Internet File System operates as an application-layer network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an...

(SMB, also known as CIFS), Apple Filing Protocol

Apple Filing Protocol

The Apple Filing Protocol is a network protocol that offers file services for Mac OS X and original Mac OS. In Mac OS X, AFP is one of several file services supported including Server Message Block , Network File System , File Transfer Protocol , and WebDAV...

(AFP), NetWare Core Protocol

NetWare Core Protocol

The NetWare Core Protocol is a network protocol used in some products from Novell, Inc. It is usually associated with the NetWare operating system, but parts of it have been implemented on other platforms such as Linux, Windows NT and various flavors of Unix.It is used to access file, print,...

(NCP), and OS/400 File Server file system (QFileSvr.400). SMB and NetWare Core Protocol

NetWare Core Protocol

(NCP) occur more commonly than NFS on systems running Microsoft Windows; AFP occurs more commonly than NFS in Macintosh systems; and QFileSvr.400 occurs more commonly in AS/400 systems.

Typical implementation

Assuming a Unix-style scenario in which one machine (the client

Client (computing)

A client is an application or system that accesses a service made available by a server. The server is often on another computer system, in which case the client accesses the service by way of a network....

) requires access to data stored on another machine (the NFS server

Server (computing)

In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...

The server implements NFS daemon
Daemon (computer software)
In Unix and other multitasking computer operating systems, a daemon is a computer program that runs as a background process, rather than being under the direct control of an interactive user...

processes (running by default as nfsd) in order to make its data generically available to clients.
The server administrator determines what to make available, exporting the names and parameters of directories
Directory (file systems)
In computing, a folder, directory, catalog, or drawer, is a virtual container originally derived from an earlier Object-oriented programming concept by the same name within a digital file system, in which groups of computer files and other folders can be kept and organized.A typical file system may...

(typically using the /etc/exports configuration file and the exportfs command).
The server security
Network security
In the field of networking, the area of network security consists of the provisions and policies adopted by the network administrator to prevent and monitor unauthorized access, misuse, modification, or denial of the computer network and network-accessible resources...

-administration ensures that it can recognize and approve validated clients.
The server network configuration ensures that appropriate clients can negotiate with it through any firewall system.
The client machine requests access to exported data, typically by issuing a mount command. (The client asks the server (rpcbind) which port the NFS server is using, the client connects to the NFS server (nfsd), nfsd passes the request to mountd)
If all goes well, users on the client machine can then view and interact with mounted filesystems on the server within the parameters permitted.

Note that automation of the NFS mounting process may take place — perhaps using /etc/fstab and/or automounting

Berkeley Automounter

The Berkeley Automounter first appeared in 4.4BSD, and is a computer automounter daemon. The original Berkeley automounter was created by Jan-Simon Pendry in 1989 and was donated to Berkeley...

facilities.

1980s

NFS and ONC figured prominently in the network-computing war between Sun Microsystems and Apollo Computer

Apollo Computer

Apollo Computer, Inc., founded 1980 in Chelmsford, Massachusetts by William Poduska and others, developed and produced Apollo/Domain workstations in the 1980s. Along with Symbolics and Sun Microsystems, Apollo was one of the first vendors of graphical workstations in the 1980s...

, and later the UNIX wars

Unix wars

The Unix wars were the struggles between vendors of the Unix computer operating system in the late 1980s and early 1990s to set the standard for Unix thenceforth.- Origins :...

(ca 1987-1996) between AT&T

AT&T

AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...

and Sun on one side, and Digital Equipment, HP

Hewlett-Packard

Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...

, and IBM

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

on the other.

During the development of the ONC protocol (called SunRPC at the time), only Apollo's Network Computing System

Network Computing System

The Network Computing System was an implementation of the Network Computing Architecture . It was created at Apollo Computer in the 1980s...

(NCS) offered comparable functionality. Two competing groups developed over fundamental differences in the two remote procedure call systems. Arguments focused on the method for data-encoding — ONC's External Data Representation

External Data Representation

External Data Representation is a standard data serialization format, for uses such as computer network protocols. It allows data to be transferred between different kinds of computer systems. Converting from the local representation to XDR is called encoding. Converting from XDR to the local...

(XDR) always rendered integers in big-endian order, even if both peers of the connection had little-endian machine-architectures, whereas NCS's method attempted to avoid byte-swap whenever two peers shared a common endianness

Endianness

In computing, the term endian or endianness refers to the ordering of individually addressable sub-components within the representation of a larger data item as stored in external memory . Each sub-component in the representation has a unique degree of significance, like the place value of digits...

in their machine-architectures. An industry-group called the Network Computing Forum formed (March 1987) in an (ultimately unsuccessful) attempt to reconcile the two network-computing environments.

Later, Sun and AT&T announced that the two firms would jointly develop AT&T's next version of UNIX: System V Release 4. This caused many of AT&T's other licensees of UNIX System V to become concerned that this would put Sun in an advantaged position, and it ultimately led to Digital Equipment, HP, IBM, and others forming the Open Software Foundation

Open Software Foundation

The Open Software Foundation was a not-for-profit organization founded in 1988 under the U.S. National Cooperative Research Act of 1984 to create an open standard for an implementation of the UNIX operating system.-History:...

(OSF) in 1988. Ironically, Sun and AT&T had previously competed over Sun's NFS versus AT&T's Remote File System

Remote File System

The Remote File System was a distributed file system developed by AT&T in the 1980s. It was first delivered with UNIX System V Release 3 .Compared to NFS it made quite different design decisions...

(RFS), and the quick adoption of NFS over RFS by Digital Equipment, HP, IBM, and many other computer vendors tipped the majority of users in favor of NFS.

OSF solicited the proposals for various technologies, including the remote procedure call

Remote procedure call

In computer science, a remote procedure call is an inter-process communication that allows a computer program to cause a subroutine or procedure to execute in another address space without the programmer explicitly coding the details for this remote interaction...

(RPC) system and the remote file access protocol. In the end, proposals for these two requirements, called respectively, the Distributed Computing Environment

Distributed Computing Environment

The Distributed Computing Environment is a software system developed in the early 1990s by a consortium that included Apollo Computer , IBM, Digital Equipment Corporation, and others. The DCE supplies a framework and toolkit for developing client/server applications...

(DCE), and the Distributed File System

DCE Distributed File System

The DCE Distributed File System is the remote file access protocol used with the Distributed Computing Environment. It was based on the AFS Version 3.0 protocol that was developed commercially by Transarc Corporation...

(DFS) won over Sun's proposed ONC and NFS. DCE derived from a suite of technologies, including NCS and Kerberos. DFS used DCE as the RPC and derived from the Andrew File System (AFS)

Andrew file system

1990s

Sun Microsystems and the Internet Society

Internet Society

The Internet Society or ISOC is an international, nonprofit organization founded during 1992 to provide direction in Internet related standards, education, and policy...

(ISOC) reached an agreement to cede "change control" of ONC RPC so that ISOC's engineering-standards body, the Internet Engineering Task Force (IETF), could publish standards documents (RFCs) documenting the ONC RPC protocols and could extend ONC RPC. OSF attempted to make DCE RPC an IETF standard, but ultimately proved unwilling to give up change control. Later, the IETF chose to extend ONC RPC by adding a new authentication flavor based on GSSAPI

Generic Security Services Application Program Interface

The Generic Security Services Application Program Interface is an application programming interface for programs to access security services....

, RPCSEC GSS, in order to meet IETF's requirements that protocol standards have adequate security.

Later, Sun and ISOC reached a similar agreement to give ISOC change control over NFS, although writing the contract carefully to exclude NFS version 2 and version 3. Instead, ISOC gained the right to add new versions to the NFS protocol, which resulted in IETF specifying NFS version 4 in 2003.

2000s

By the 21st century, neither DFS nor AFS had achieved any major commercial success as compared to CIFS or NFS. IBM, which had previously acquired the primary commercial vendor of DFS and AFS, Transarc

Transarc

Transarc Corporation was a private Pittsburgh-based software company founded in 1989 by Jeffrey Eppinger, Michael Kazar, Alfred Spector, and Dean Thompson of Carnegie Mellon University...

, donated most of the AFS source code to the free software community

Free software community

The free-software community is an informal term that refers to the users and developers of free software as well as supporters of the free-software movement. The movement is sometimes referred to as the open-source software community or a subset thereof...

in 2000. The OpenAFS

OpenAFS

OpenAFS is an open source implementation of the Andrew distributed file system . AFS was originally developed at Carnegie Mellon University, and developed as a commercial product by the Transarc Corporation, which was subsequently acquired by IBM. At LinuxWorld on 15 August 2000, IBM their plans...

project lives on. In early 2005, IBM announced end of sales for AFS and DFS.

Present

NFSv4.1 adds the Parallel NFS pNFS capability, which enables data access parallelism. The NFSv4.1 protocol defines a method of separating the filesystem meta-data from the location of the file data; it goes beyond the simple name/data separation by striping the data amongst a set of data servers. This is different from the traditional NFS server which holds the names of files and their data under the single umbrella of the server. There exist products which are multi-node NFS servers, but the participation of the client in separation of meta-data and data is limited. The NFSv4.1 client can be enabled to be a direct participant in the exact location of file data and avoid solitary interaction with the single NFS server when moving data.

The NFSv4.1 pNFS server is a collection of server resources or components; these are assumed to be controlled by the meta-data server.

The pNFS client still accesses a single meta-data server for traversal or interaction with the namespace; when the client moves data to and from the server it may be directly interacting with the set of data servers belonging to the pNFS server collection.

In addition to pNFS, NFSv4.1 provides Sessions, Directory Delegation and Notifications, Multi-server Namespace, ACL/SACL/DACL, Retention Attributions, and SECINFO_NO_NAME.

External links

RFCs
- RFC 5661 - Network File System (NFS) Version 4 Minor Version 1 Protocol
- RFC 3530 - NFS Version 4 Protocol Specification
- RFC 2054 - WebNFS Specification
- RFC 2339 - Sun/ISOC NFS Change Control Agreement
- RFC 2203 - RPCSEC_GSS Specification
- RFC 1813 - NFS Version 3 Protocol Specification
- RFC 1790 - Sun/ISOC ONC RPC Change Control Agreement
- RFC 1094 - NFS Version 2 Protocol Specification
IETF: Network File System Version 4 (nfsv4) Charter
Linux NFS Overview, FAQ and HOWTO Documents
- - IBM: NFSv4 delivers seamless network access
  - NFS operation explained with sequence diagrams
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