Linux and Technology blog

August 7, 2006

Reiser4 and the politics of the kernel

Filed under: Kernel, News, Reviews — rakeshvk @ 6:31 pm

Why is the Reiser4 filesystem not in the Linux kernel? Recently, the question has been discussed on the kernel mailing list, and it’s not a pretty sight; anyone who imagines that kernel development is a rational discourse only needs to look at the exchange to be disillusioned. While both sides claim to be arguing technical merits, the discussion spills over into a debate about the advantages of established procedures and policies. It’s also turned into a clash of personalities.

Reiser4 is the successor to ReiserFS (a.k.a. Reiser3), a journaled filesystem that has been in the kernel since version 2.4.1, and that also faced a rocky road to inclusion. Both are developed by Namesys, a company fronted by Hans Reiser, with sponsorship from Linspire and the Defense Advance Research Projects Agency. According to Namesys, Reiser4 offers twice the speed of other filesystems, as well as greater efficiency in file allocation and military-grade security. It has attracted a loyal group of users, and, while not in the official kernel, is included in Andrew Morton’s experimental -mm kernel sources. >>>>

Reasons why Reiser4 is great for you:

  • Reiser4 is the fastest filesystem, and here are the benchmarks.
  • Reiser4 is an atomic filesystem, which means that your filesystem operations either entirely occur, or they entirely don’t, and they don’t corrupt due to half occuring. We do this without significant performance losses, because we invented algorithms to do it without copying the data twice.
  • Reiser4 uses dancing trees, which obsolete the balanced tree algorithms used in databases (see farther down). This makes Reiser4 more space efficient than other filesystems because we squish small files together rather than wasting space due to block alignment like they do. It also means that Reiser4 scales better than any other filesystem. Do you want a million files in a directory, and want to create them fast? No problem.
  • Reiser4 is based on plugins, which means that it will attract many outside contributors, and you’ll be able to upgrade to their innovations without reformatting your disk. If you like to code, you’ll really like plugins….
  • Reiser4 is architected for military grade security. You’ll find it is easy to audit the code, and that assertions guard the entrance to every function.

V3 of reiserfs is used as the default filesystem for SuSE, Lindows, FTOSX, Libranet, Xandros and Yoper. We don’t touch the V3 code except to fix a bug, and as a result we don’t get bug reports for the current mainstream kernel version. It shipped before the other journaling filesystems for Linux, and is the most stable of them as a result of having been out the longest. We must caution that just as Linux 2.6 is not yet as stable as Linux 2.4, it will also be some substantial time before V4 is as stable as V3.


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