computer science

List of log-structured file systems

List of log-structured file systems 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 List of log-structured file systems rather than just read about it. In short: This is an incomplete list of log-structured file system implementations. James T, Brady while in IBM Poughkeepsie Lab conceived a log structured paging file system in 1979 which was implemented in MVS SP2 in 1980.

Key takeaways

List of log-structured file systems 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 List of log-structured file systems to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of List of log-structured file systems from memory before moving on to harder problems.

Reference excerpt

This is an incomplete list of log-structured file system implementations.

James T, Brady while in IBM Poughkeepsie Lab conceived a log structured paging file system in 1979 which was implemented in MVS SP2 in 1980. John K. Ousterhout and Mendel Rosenblum implemented the first log-structured file system for the Sprite operating system in 1992. BSD-LFS, an implementation by Margo Seltzer was added to 4.4BSD, and was later ported to 386BSD. It lacked support for snapshots. It was removed from FreeBSD and OpenBSD, but still lives on in NetBSD. Plan 9's Fossil file system is also log-structured and supports snapshots. NILFS is a log-structured file system implementation for Linux by NTT/Verio which supports snapshots. LinLogFS (formerly dtfs) and LFS are log-structured file system implementations for Linux. The latter was part of Google Summer of Code 2005. Both projects have been abandoned. LFS is another log-structured file system for Linux developed by Charles University, Prague. It was to include support for snapshots and indexed directories, but development has since ceased. Write Anywhere File Layout (WAFL) by NetApp is a file layout that supports large, high-performance RAID arrays, quick restarts without lengthy consistency checks in the event of a crash or power failure, and growing the filesystems size quickly. Built using log-structured file system concept, snapshots and off-line data deduplication. LSFS is a log-structured file system with writable snapshots and inline data deduplication created by StarWind Software. Cache Accelerated Sequential Layout (CASL) is a proprietary log-structured filesystem developed by Nimble Storage that uses Solid State Devices to cache traditional hard drives. ZeroFS is a OpenSource log-structured filesystem that presents S3-compatible object storage as traditional file and block interfaces via NFS, 9P, and NBD servers, with built-in XChaCha20-Poly1305 encryption and LZ4/Zstd compression. ObjectiveFS is a log-structured FUSE filesystem that uses cloud object stores (e.g. Amazon S3, Google Cloud Storage and private cloud object store). NOVA for byte-addressable persistent memory (for example non-volatile dual in-line memory module (NVDIMM) and 3D XPoint) for Linux developed at the University of California, San Diego, US. Spiralog was a log-structured filesystem created by Digital Equipment Corporation for the OpenVMS operating system. Spiralog was an optional product, and was discontinued due to a variety of problems, including issues with handling full volumes. Some kinds of storage media, such as flash memory and CD-RW, slowly degrade as they are written to and have a limited number of erase/write cycles at any one location. Log-structured file systems are sometimes used on these media because they make fewer in-place writes and thus prolong the life of the device by wear leveling. The more common such file systems include:

UDF is a file system commonly used on optical discs. JFFS and its successor JFFS2 are simple Linux file systems intended for raw flash-based devices. UBIFS is a filesystem for raw NAND flash media and also intended to replace JFFS2. LogFS is a scalable flash filesystem for Linux that works on both raw flash media and block devices, intended to replace JFFS2. YAFFS is a raw NAND flash-specific file system for many operating systems (including Linux). F2FS is a new file system designed for the NAND flash memory-based storage devices on Linux.

Worked examples

Example 1 — a first encounter with List of log-structured file systems

Start with the simplest possible case. Write down what List of log-structured file systems 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 List of log-structured file systems 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 List of log-structured file systems 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 List of log-structured file systems

In research: List of log-structured file systems 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 List of log-structured file systems 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: List of log-structured file systems is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer file systems, Computing-related lists, Lists of software, so understanding it makes those chapters shorter.
In everyday life: Look for List of log-structured file systems 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 List of log-structured file systems in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what List of log-structured file systems 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 List of log-structured file systems out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is List of log-structured file systems in simple terms?

This is an incomplete list of log-structured file system implementations. James T, Brady while in IBM Poughkeepsie Lab conceived a log structured paging file system in 1979 which was implemented in MVS SP2 in 1980.

Why does List of log-structured file systems 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 List of log-structured file systems?

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 List of log-structured file systems.