computer science

Network File System

Network File System is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Network File System rather than just read about it. In short: Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems (Sun) in 1984, allowing a user on a client computer to access files over a computer network much like local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system.

Key takeaways

Network File System belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Network File System to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Network File System from memory before moving on to harder problems.

Reference excerpt

Network File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems (Sun) in 1984, allowing a user on a client computer to access files over a computer network much like local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. NFS is an open IETF standard. After the first experimental version developed in house at Sun Microsystems, all subsequent versions of the protocol are defined in a series of Request for Comments i.e. RFCs, allowing anyone to implement the protocol.

Versions and variations 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 only over User Datagram Protocol (UDP). Its designers meant to keep the server side stateless, with locking (for example) implemented outside of the core protocol. People involved in the creation of NFS version 2 include Russel Sandberg, Bob Lyon, Bill Joy, Steve Kleiman, and others. The Virtual File System interface allows a modular implementation, reflected in a simple protocol. By February 1986, implementations were demonstrated for operating systems such as System V release 2, DOS, and VAX/VMS using Eunice. NFSv2 only allows the first 2 GB of a file to be read due to 32-bit limitations.

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. The first NFS Version 3 proposal within Sun Microsystems was created not long after the release of NFS Version 2. The principal motivation was an attempt to mitigate the performance issue of the synchronous write operation in NFS Version 2. By July 1992, implementation practice had solved many shortcomings of NFS Version 2, leaving only lack of large file support (64-bit file sizes and offsets) a pressing issue. 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 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 more feasible, and allowed the use of larger read and write transfer sizes beyond the 8 KB limit imposed by User Datagram Protocol.

YANFS/WebNFS

YANFS (Yet Another NFS), formerly WebNFS, is an extension to NFSv2 and NFSv3 allowing it to function behind restrictive firewalls without the complexity of Portmap and MOUNT protocols. YANFS/WebNFS has a fixed TCP/UDP port number (2049), and instead of requiring the client to contact the MOUNT RPC service to determine the initial filehandle of every filesystem, it introduced the concept of a public filehandle (null for NFSv2, zero-length for NFSv3) which could be used as the starting point. Both of those changes were later incorporated into NFSv4. YANFS's post-WebNFS development has also included server-side integration.

NFSv4 Version 4 (RFC 3010, December 2000; revised in RFC 3530, April 2003 and again in RFC 7530, March 2015), influenced by Andrew File System (AFS) and Server Message Block (SMB), 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 Microsystems handed over the development of the NFS protocols. NFS version 4.1 (RFC 5661, January 2010; revised in RFC 8881, August 2020) 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). Version 4.1 includes Session trunking mechanism (Also known as NFS Multipathing) and is available in some enterprise solutions as VMware ESXi. NFS version 4.2 (RFC 7862) was published in November 2016 with new features including: server-side clone and copy, application I/O advise, sparse files, space reservation, application data block (ADB), labeled NFS with sec_label that accommodates any MAC security system, and two new operations for pNFS (LAYOUTERROR and LAYOUTSTATS). One big advantage of NFSv4 over its predecessors is that only one UDP or TCP port, 2049, is used to run the service, which simplifies using the protocol across firewalls.

Other extensions WebNFS, 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. Note:

the byte-range advisory Network Lock Manager (NLM) protocol (added to support UNIX System V file locking APIs) the remote quota-reporting (RQUOTAD) protocol, which allows NFS users to view their data-storage quotas on NFS servers NFS over RDMA, an adaptation of NFS that uses remote direct memory access (RDMA) as a transport NFS-Ganesha, an NFS server, running in user-space and supporting various file systems like GPFS/Spectrum Scale, CephFS via respective FSAL (File System Abstraction Layer) modules. The CephFS FSAL is supported using libcephfs Trusted NFS (TNFS)

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Network File System

Start with the simplest possible case. Write down what Network File System claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Network File System before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Network File System ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Network File System

In research: Network File System appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Network File System in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Network File System is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1984 software, Application layer protocols, Distributed file systems, so understanding it makes those chapters shorter.
In everyday life: Look for Network File System outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Network File System in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Network File System means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Network File System out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Network File System in simple terms?

Why does Network File System matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Network File System?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Network File System.