Reiser File System

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ReiserFS
Manufacturer Namesys ( Hans Reiser )
Full name Reiser File System
Technical implementation
Directories B⁺ tree (ReiserFS 1-3) B * tree (Reiser4)
Files bitmap
Maximum values
Size of a file 2 31 bytes (2 GiB ) (version 3.5)
2 60 bytes (1 EiB ) (version 3.6)
Number of all files 2 32 - 3
Length of the file name Block size - 64 (a block size of 4 KB results in 4032 bytes)
properties
Supporting operating systems Linux, BSD

ReiserFS is a multi-purpose file system that was developed and implemented in 2001 by a group of developers around Hans Reiser in the Namesys company, which he owns . The Reiser File System is subject to the General Public License . The development of version 3 was supported by MP3.com and SuSE Linux GmbH , version 4 mainly by DARPA and Linspire .

ReiserFS was the first journaling file system that was included as standard in the Linux kernel (from kernel version 2.4.1). It is mainly used for logical volumes or RAID systems.

Version 4 of ReiserFS is currently fully supported by the Linux kernel. There is experimental support for FreeBSD , so far only for read operations. Commercial drivers are also available for Microsoft's operating systems .

ReiserFS, versions 1 and 2

The ReiserFS is based on the data structure of the B + tree developed by Rudolf Bayer . This applies to versions 1 to 3.

ReiserFS, version 3

In version 3 a journal was added to the ReiserFS. Originally, a disadvantage of ReiserFS compared to some other journaling systems was that journaling was only available for the meta information , i. H. for the directories and management sectors, but not for the payload in the files themselves. This has been fixed in the 2.6 kernel.

Reiser4

Reiser4 is completely new and should not be confused with the old ReiserFS. Therefore it is not marketed as "ReiserFS 4". A modification of the B * tree structure is used, so-called dancing trees . The main difference is that underfilled nodes are not merged with every modification of the tree, but only when a write-back to permanent storage is required due to a shortage of memory or a transaction has been completed.

Reiser4 offers a speed advantage because it no longer writes the data twice on the hard drive - first in the journal and then in the file system. Instead, it saves the user data in a moving journal, which means that it is written directly to the intended location in the file system and the journal is placed on top of it until the process is complete.

Furthermore, a flexible plug-in structure has been added, through which special metadata types, encryption and compression can be implemented. On Reiser4, file metadata, such as the title and artist of a music file, can be stored in the file system rather than in applications. The difference to, for example, ID3 tags from MP3 files and comparable metadata systems is that a metadata system is integrated in the file system and not in the container format of the file, which could be the same for all files. If this approach were ever accomplished, there would be no need to worry about whether an application understands all of the types of metadata it might come into contact with. It could access the metadata transparently via a function of the file system. While this could improve application compatibility, it makes file system compatibility more difficult since the metadata cannot be copied to another file system without that metadata system, such as ext4 , XFS, or FAT32 . Also NTFS supports such alternatives streams .

Basic ReiserFS functions

Technical specifications
Version 3.5 Version 3.6
Max. Number of files per directory 518701895 (~ 2 29 ) 2 32 - 3
(limited by a hash function that
allows 1,200,000 file names without collisions)
Max. Number of hard links per file 2 16 2 32
Max. File system size 2 32 4k blocks

ReiserFS offers advantages over other file systems, especially when it comes to handling a large number of small files , as these can be stored in the management nodes (as with NTFS in the MFT). This means that the files take up less space in the file system and the space on the hard disk can be used more efficiently . These functions of the file system can be specified via the parameters when mounting . The best known parameters are:

notail Disables the storage of small files in the inodes of the directories in which they are located. This also eliminates one of the essential properties that ReiserFS recommends for small files.
nolog Deactivating journaling offers a small performance gain at the expense of security. Journaling is still carried out with this option, because this function is still under development.

There are also programs supplied by the developers for the management and administration of the file system, the reiserfsprogs :

mkreiserfs With this program a ReiserFS is created on a partition. For example, the following command creates /dev/hda1a ReiserFS on partition :
mkreiserfs / dev / hda1
During creation, parameters can be passed to this program in order to optimize the file system. However, most of them can always be changed later using some of the programs.
reiserfsck This program can be used to check the file allocation structure of the ReiserFS. Thanks to its nature as a journaling file system, checking the file system takes significantly less time than with a normal file system.
resize_reiserfs With this program, an existing ReiserFS can be subsequently varied in size. Normally, a file system always takes up the full size of the partition available to it . But this is not always desired.
reiserfstune This program can also be used to control various properties that help optimize special applications.
debugreiserfs This program is an analysis tool for debugging .

See also

Web links

Single receipts

  1. ↑ ReiserFS - Node Layout ( Memento from June 14, 2006 in the Internet Archive )
  2. ^ Reiser4 FS Wiki. Retrieved October 9, 2019 .
  3. ↑ Reiser4 file system for Linux OS - Browse /reiser4-for-linux-5.x at SourceForge.net. Retrieved October 9, 2019 .
  4. ^ Why a New Filesystem Matters. In: Kuro5hin. August 9, 2003, accessed October 4, 2010 .
  5. ↑ The Reiser4 Filesystem: Ways In Which Extra Rigor In Scientific Methodology Can Consume Years Of Your Life, And How The Result Can Be So Very Worthwhile, Abstract , Video ( Memento of August 13, 2010 in the Internet Archive ) - Lecture by Hans Reiser from Stanford University .
  6. ↑ blogs.technet.com: Jeff Hughes, The Four Stages of NTFS File Growth (2009)