ReiserFS

The ReiserFS is a general-purpose computer file system designed and implemented by a team at Namesys led by Hans Reiser, who is referred to as the project's Benevolent Dictator for Life. It is currently supported by Linux and may be included in other operating systems in the future. Introduced with version 2.4.1 of the Linux kernel, it was the first journaling file system to be included in the standard kernel.

The most-publicised advantage over what was the stock Linux file system at the time, ext2, is that it uses a transaction journal to record changes to filesystem structures. The journal allows the filesystem to quickly return to a consistent state after an unscheduled system shutdown caused by a hard reboot or a system crash. This feature greatly reduces the risk of filesystem corruption (and the need for lengthy file system checks). ReiserFS uses a balanced tree (B+ Tree) structure, which allows for storing directories containing huge numbers of small files very efficiently both in terms of speed and disk space used. Compared to ext2 and ext3 when dealing with files under 4k, ReiserFS is often faster by a factor of 10–15. This is important, for example, when handling Usenet news spools.

Unfortunately, converting to a ReiserFS file system commonly requires users of ext2 to completely reformat their disks, which is a disadvantage not shared by its main competitor ext3. It is more challenging, but there are several utilities that can be used to convert the filesystem without the need to reformat.

Due to its advantages, many Linux distributions (e.g., SuSE, Xandros, Yoper, Linspire/Lindows, FTOSX and Libranet) have made it the default file system.

With the introduction of the Reiser4 filesystem, ReiserFS is occasionally referred to as Reiser3.

Bad block handling

ReiserFS had no bad block handling prior to release 3.6.12. The bad block handling is still restricted to bad blocks in the data area. Bad blocks in the system area - super block, journal and bitmap areas cannot be handled, and may result in an unusable filesystem. The bad block handling in ReiserFS is described more in detail here.

See also

• Comparison of file systems

External links

• ReiserFS homepage
• ReiserFS dangerous on commodity PC hardware