DFS (Distributed File System) and AFS (Andrew File System)

AFS was developed in the 1980s at Carnegie Mellon University (CMU). It had several significant differences to Sun's NFS, which was the dominant remote file system at the time:

• AFS has a unified name space, where files and filesystems would have identical names wherever they are accessed ("mounted"). The convention was typically /afs/domain/... .
• AFS ran over TCP, a reliable byte-stream protocol, rather than UDP. This made AFS more suitable to use over wide-area network paths.
• AFS allows clients to cache files locally, which allows disconnected operation and has some performance benefits, but weakens consistency assurances compared to other distributed file systems.

A company called Transarc was spun off of CMU to turn AFS into a commercial product. It was further developed into DFS (Distributed File System), which was submitted to the OSF (Open Software Foundation) protocol suite. Therefore, many OSF participants, including Microsoft, have implemented DFS. Transarc was later acquired by IBM, which still supports AFS/DFS.

In addition to the Transarc/IBM implementation, there is an open source implementation called OpenAFS. This is supported on a wide range of operating systems including many versions of Unix and Windows.

References

• AFS article on Wikipedia
• OpenAFS article on Wikipedia

– Main.SimonLeinen - 25 May 2008