Reiser file system

Reiser file system
The Reiser file system was created by Hans Reiser. The design objectives were to increase performance over the ext2 file system, offer a space efficient file system, and to improve handling of large directories compared to existing file systems. Reiserfs uses balanced trees to store files and directories and it also offers journaling.

This document describes the on-disk structure of the Reiser file system version 3.6. This document does not describe how the file system tree is balanced, how the journaling is performed, or how files and directories are managed within an implementation of the file system.

Blocks
The reiserfs partition is divided into blocks of a fixed size. The blocks are numbered sequentially starting with block 0. There is a maximum number of 2^32 possible blocks in one partition.
The partition starts with the first 64k unused to leave enough room for partition labels or boot loaders. After that follows the superblock. The superblock contains important information about the partition such as the block size and the block numbers of the root and journal nodes. The superblock block number differs depending on the block size, but always starts at byte 65536 of the partition. The default block size for reiserfs under Linux is 4096 bytes. This makes the superblock block number 16. There is only one instance of the superblock for the entire partition.

Directly following the superblock is a block containing a bitmap of free blocks. The number of blocks mapped in the bitmap depends directly on the block size. If a bitmap can map k blocks, then every k-th block will be a new bitmap block
For more information about Reiser file system goto http://homes.cerias.purdue.edu/~florian/reiser/reiserfs.php