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'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.
As of 2007, 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 much more widely adopted. Reiser4 is also available from Andrew Morton's -mm kernel sources. Linux kernel developers claim that Reiser4 breaks Linux coding standards,^[1] but Hans Reiser suggests political reasons.

Contents

Features

Performance

References

See also

External links

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 tail packing

★ 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; sooner if someone pays them to do so. Re: Benchmark : ext3 vs reiser4 and effects of fragmentation.

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.^[2] Other benchmarks show results of Reiser4 being slower on many operations.^[3]

References

1. Linux: Why Reiser4 Is Not in the Kernel
2. Benchmarks Of ReiserFS Version 4 Hans Reiser
3. Benchmarking Filesystems Part II Justin Piszcz

See also

★ ReiserFS

★ List of file systems

★ Comparison of file systems

External links

★ Reiser4 homepage

★ Introduction to Reiser4 on kuro5hin

★ Getting started with Reiser4 from Namesys.com

★ Programmer's Guide to Reiser4

★ 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 on Linux.com