Reiser4

From Wikipedia, the free encyclopedia

Reiser4
Developer Namesys
Full name Reiser4
Introduced 2004 (Linux)
Partition identifier Apple_UNIX_SVR2 (Apple Partition Map)

0x83 (MBR)
EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 (GPT)
Structures
Directory contents Dancing B*-tree
File allocation
Bad blocks
Limits
Max file size 8 TiB on x86
Max number of files
Max filename length 3976 bytes
Max volume size
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]
Date resolution
Forks Extended attributes
Attributes
File system permissions Unix permissions, ACLs and arbitrary security attributes
Transparent compression Version 4
Transparent encryption Version 4
Supported operating systems Linux

Reiser4 is a computer file system, a new "from scratch" successor to the ReiserFS file system, developed by Namesys and sponsored by DARPA as well as Linspire.

Contents

[edit] Features

Some of the goals of the Reiser4 file system are:

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; 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, 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 2008, 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] After Hans Reiser's imprisonment, some hard-to-spot bugs introduced by kernel developers have been found to corrupt key elements of Reiser4. [7]

[edit] Future of ReiserFS

Hans Reiser was convicted of murder on April 28th, 2008, leaving uncertainty over the future of Reiser4. 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[8]; 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 continue development of Reiser4 and source code is available from Shishkin's Web site.[9]

[edit] See also

[edit] References

  1. ^ Documentation/filesystems/reiser4.txt from a reiser4-patched kernel source, "By default file in reiser4 have 64 bit timestamps."
  2. ^ Reiser, Hans (2004-09-16). Re: Benchmark : ext3 vs reiser4 and effects of fragmentation.. Namesys, ReiserFS mailing list. Retrieved on 2006-10-13.
  3. ^ Hans Reiser (November 20, 2003). Benchmarks Of ReiserFS Version 4. Namesys. Retrieved on 2006-11-28.
  4. ^ Justin Piszcz (January 2006). Benchmarking Filesystems Part II. Retrieved on 2006-04-23.
  5. ^ Linux: Why Reiser4 Is Not in the Kernel. Kerneltrap (September 19, 2005).
  6. ^ Reiser, Hans (21 July 2006). The "'official' point of view" expressed by kernelnewbies.org regarding reiser4 inclusion. Retrieved on 2008-03-01.
  7. ^ Phoronix forums: Possible sabotage of Reiser4
  8. ^ Murder Suspect Selling Namesys. Wired News (2006-12-21). Retrieved on 2006-12-30.
  9. ^ 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.

[edit] External links