Log-structured File System - Implementations

Implementations

  • 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 (http://logfs.sourceforge.net/) 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.
  • ULFS is a User-Level Log-structured File System (http://ulfs.sf.net) using FUSE (http://fuse.sf.net).
  • CASL is a proprietary log-structured filesystem that uses Solid State Devices to cache traditional hard drives (http://www.nimblestorage.com/products/architecture/).
  • SISL is a log-structured filesystem with deduplication and was designed by DataDomain (http://www.datadomain.com/products/SISL.html).

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.

Read more about this topic:  Log-structured File System