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 April 24, 2006 , Reiser4 still has not been merged into the mainline
Linux Kernel due to
Coding Style issues and consequently is not supported on many
Linux Distribution s; however, its predecessor Reiser3 has been much more widely adopted. Namesys has made inclusion into the mainline Linux kernel its first priority.
- 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 )
- 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), or the capability of resizing existing file systems, (common in Linux file systems, including ReiserFS version 3); the creators of Reiser4 say they will implement these if someone pays them to do so.
- -tree" class="copylinks">B
tree s 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 its most serious competitor
Ext3 working on files smaller than 1Kb. It is typically twice the performance of ext3 for general purpose filesystem usage patterns,
