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  Name Reiser4
  Full Name Reiser4
  Developer Namesys
  Introduction Os Linux
  OS Linux
  Introduction Date 2004
  Directory Struct Dancing B-tree
  Max Filename Size 3976 bytes
  Max File Size 8 TiB on x86
  Filename Character Set All bytes except NUL and '/'
  Dates Recorded modification (mtime), metadata change (ctime), access (atime)
  Date Range 64-bit timestampsDocumentation/filesystems/reiser4txt from a reiser4-patched kernel source, "By default file in reiser4 have 64 bit timestamps"
  Forks Streams Extended attributes
  File System Permissions Unix permissions, ACL s and arbitrary security attributes
  Compression Version 41 (beta)
  Encryption Version 41 (beta)


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 Distribution s; 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.


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


PERFORMANCE

  • -tree" class="copylinks">B
    tree s 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.