Reiser4
From Wikipedia, the free encyclopedia
| Developer | Namesys |
|---|---|
| Full name | Reiser4 |
| Introduced | 2004 (Linux) |
| Partition identifier | Apple_UNIX_SVR2 (Apple Partition Map) 0x83 (MBR) |
| Structures | |
| Directory contents | Dancing B*-tree |
| Limits | |
| Max file size | 8 TiB on x86 |
| Max filename length | 3976 bytes |
| Allowed characters in filenames | All bytes except NUL and '/' |
| Features | |
| Dates recorded | modification (mtime), metadata change (ctime), access (atime) |
| Date range | 64-bit timestamps[1] |
| Forks | Extended attributes |
| File system permissions | Unix permissions, ACLs and arbitrary security attributes |
| Transparent compression | Yes |
| Transparent encryption | Yes |
| Single Instance Storage | No |
| Supported operating systems | Linux |
Reiser4 is a computer file system, successor to the ReiserFS file system, developed from scratch by Namesys and sponsored by DARPA as well as Linspire. It is named after its creator Hans Reiser.
Contents |
[edit] Features
Some of the goals of the Reiser4 file system are:
- More efficient journaling through wandering logs
- More efficient support of small files, in terms of disk space and speed through block suballocation
- Faster handling of directories with large numbers of files
- Flexible plugin infrastructure (through which special metadata types, encryption and compression will be supported)
- Dynamically optimized disk-layout through allocate-on-flush (also called delayed allocation in XFS)
- Transaction support
Some of the more advanced Reiser4 features (such as user-defined transactions) are also not available because of a lack of a VFS API for them.
At present Reiser4 lacks a few standard file system features, such as an online repacker (similar to the defragmentation utilities provided with other file systems). The creators of Reiser4 say they will implement these later, or sooner if someone pays them to do so.[2]
[edit] Performance
Reiser4 uses B*-trees in conjunction with the dancing tree balancing approach, in which underpopulated nodes will not get merged until a flush to disk except under memory pressure or when a transaction completes. Such a system also allows Reiser4 to create files and directories without having to waste time and space through fixed blocks.
As of 2004[update], synthetic benchmarks performed by Namesys show that Reiser4 is 10 to 15 times faster than its most serious competitor ext3 working on files smaller than 1 KiB. Namesys's benchmarks suggest it is typically twice the performance of ext3 for general-purpose filesystem usage patterns.[3] Other benchmarks show results of Reiser4 being slower on many operations.[4]
[edit] Integration with Linux
As of 2009[update], Reiser4 has not yet been merged into the mainline Linux kernel and consequently is still not supported on many Linux distributions; however, its predecessor ReiserFS v3 has been widely adopted. Reiser4 is also available from Andrew Morton's -mm kernel sources. Linux kernel developers claim that Reiser4 does not follow Linux coding standards,[5] but Hans Reiser suggests political reasons.[6]
[edit] Future of Reiser4
Hans Reiser was convicted of murder on April 28th, 2008, leaving the future of Reiser4 uncertain. After his arrest, employees of Namesys assured they would continue to work and that the events would not slow down the software development in the immediate future. In order to afford increasing legal fees, Hans Reiser announced on December 21, 2006 that he was going to sell Namesys;[7] as of March 26, 2008, it has not been sold, although the website is unavailable. In January 2008, Edward Shishkin, an employee of and programmer for Namesys, was quoted in a CNET interview saying that "Commercial activity of Namesys has stopped." Shishkin and others continued the development of Reiser4,[8] making source code available from Shishkin's web site,[9] later relocated to kernel.org.[10]
As of August 2008[update], Reiser4 development still continues without Namesys. However, kernel developer Theodore Ts'o has suggested btrfs as an alternative for those interested in the design ideas of Reiser4.[11]
[edit] See also
[edit] References
- ^ Documentation/filesystems/reiser4.txt from a reiser4-patched kernel source, "By default file in reiser4 have 64-bit timestamps."
- ^ Reiser, Hans (2004-09-16). "Re: Benchmark: ext3 vs reiser4 and effects of fragmentation.". Namesys, ReiserFS mailing list. http://www.xy1.org/reiserfs-list@namesys.com/msg04018.html. Retrieved on 2006-10-13.
- ^ Hans Reiser (November 20, 2003). "Benchmarks Of ReiserFS Version 4". Namesys. http://www.namesys.com/benchmarks.html. Retrieved on 2006-11-28.
- ^ Justin Piszcz (January 2006). "Benchmarking Filesystems Part II". http://linuxgazette.net/122/TWDT.html#piszcz. Retrieved on 2006-04-23.
- ^ "Linux: Why Reiser4 Is Not in the Kernel". Kerneltrap. September 19, 2005. http://kerneltrap.org/node/6844.
- ^ Reiser, Hans (21 July 2006). "The "'official' point of view" expressed by kernelnewbies.org regarding reiser4 inclusion". http://lkml.org/lkml/2006/7/21/109. Retrieved on 2008-03-01.
- ^ "Murder Suspect Selling Namesys". Wired News. 2006-12-21. http://www.wired.com/news/technology/0,72342-0.html?tw=wn_technology_1. Retrieved on 2006-12-30.
- ^ Namesys vanishes, but ReiserFS project lives on. http://www.news.com/8301-13580_3-9851703-39.html CNet (January 16, 2008). Retrieved on 2008-01-26.
- ^ http://chichkin_i.zelnet.ru/namesys/
- ^ New location of Namesys software Linux Kernel Mailing List post, 2008-08-04
- ^ Kernel Trap: Reiser4 Update. August 6, 2008.
[edit] External links
- Current Reiserfs4 patches as Namesys' website is down
- Reiserfs v4 utilities and Reiserfs v3 utilities source code repository
- Compiling a new kernel with Reiser4
- Reiser4 homepage (Archive copy at the Internet Archive) is now offline but try a cached version (without figures).
- Introduction to Reiser4 on kuro5hin
- Reiser4 transaction design document
- Trees in the Reiser4 Filesystem, Part I from Linux Journal
- Trees in the Reiser4 Filesystem, Part II from Linux Journal
- Hans Reiser: The Reiser4 Filesystem Hans Reiser's lecture at Google
- Why Reiser4 is not in the Linux Kernel at kernelnewbies.org and Hans Reiser's response to Kernelnewbies' criticism
- Reiser4 and the Politics of the Kernel by Bruce Byfield on Linux.com
