AtheOS File System

The AtheOS file system (AFS) was originally used in the AtheOS operating system, and is now a part of the Syllable operating system. It is an extension of the Be File System used in BeOS. AFS started with exactly the same data structures as BFS, and extended the feature set of BFS in many ways. As such, AFS is a 64-bit journaled file system with support for file attributes. File indexing and soft deletions are also partially supported.

A few definitions:

• Journaled -- All file system transactions are first written to a journal before they are carried out. The file system replays everything in the journal when mounted. So, if something catastrophic occurs while data's being written to the file system, the file system can recover.
• File Attributes -- Name/value pairs tacked on to a file. For example, an MP3 file might have attributes for Artist, Title, and Album. This allows the file system to search files in intelligent and flexible ways (such as a search for all songs by Elton John that exist on the hard drive).
• File Indexing -- A persistent and up-to-date list of all files that have a particular attribute, and the value of that attribute. So, the system may have an index for the Artist attribute on MP3 files. This speeds up searching, but slows down system performance when large numbers of files are created.
• Soft Deletions -- When the file system is told to delete a file, the file is actually hidden, and removed later by other means. In AFS, files are moved to an invisible directory and only deleted when the file system is next mounted.

Links

http://www.atheos.cx/ http://www.myelin.co.nz/atheos/ http://atheos.s5.com/ http://www.azaka.org/