Reiser4
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Reiser4 is a computer file system, a new "from scratch" version of the ReiserFS file system, developed by Namesys and sponsored by DARPA as well as Linspire.
As of June 2005, Reiser4 still has not been merged into the mainline Linux kernel and consequently is not supported on many Linux distributions; however, its predecessor has been much more widely adopted.
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Features
- efficient journaling through wandering logs
- efficient support of small files, in terms of disk space and speed
- fast handling of very large directories with hundreds of millions of files
- flexible plugin infrastructure (through which special metadata types, encryption and compression will be supported)
- atomic file system modification
- dynamically optimized disk-layout through allocate-on-flush (also called delayed allocation in XFS)
- an online repacker (similar to the defragmentation utilities provided with other filesystems)
- 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.
Performance
Reiser4 uses dancing trees, a version of B*-trees in which underpopulated nodes won't 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, Benchmarks performed by Namesys show that Reiser4 is 10 to 15 times faster than Ext3 working on files smaller than 1Kb.
See also
External links
- Reiser4 homepage (http://www.namesys.com/v4/v4.html)
- introduction to Reiser4 on kuro5hin (http://www.kuro5hin.org/story/2003/8/9/172159/7912)
- Getting started with Reiser4 (http://www.namesys.com/install_v4.html) from Namesys.com
- How to install Reiser4 on Gentoo (http://gentoo-wiki.com/HOWTO_ReiserFS_4)de:Reiser4