Coda (file system)

Coda is a distributed filesystem, developed at Carnegie Mellon University since 1987, under the direction of Mahadev Satyanarayanan. It is based on the older AFS, a similar but less advanced distributed file system.

Major features include:

Disconnected operation – Disconnect from the file server and carry on working
Client-side caching – Improves performance by reducing the need to fetch data from the server
Replication – Store and manipulate the same data on multiple servers, to improve reliability and scalability
Security – Uses a security system derived from Kerberos
Well-defined semantics of sharing, even with network failures
Native support in the Linux 2.6 kernel (as opposed to AFS or NFS3)

Major misfeatures of the standard CMU implementation:

The server software maps its RVM metadata to memory, meaning it occupies about 4% of the maximum served disk space in memory (!). Also, RVM metadata is limited to about 300MB, resulting in a maximum volume size of about 8GB.

The emphasis of the Coda development appears to be on moving from a very good research project to a filesystem ready for production use.

External links