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 an older version of AFS, a similar but in some aspects 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 interoperable with among others Kerberos
- Well-defined semantics of sharing, even with network failures
- Native support in the Linux 2.6 kernel (as opposed to AFS)
Major misfeatures of the standard CMU implementation:
- The server software maps its metadata to virtual memory, limiting its size to about 1GB, resulting in a maximum number of files per server being in the order of 10^6 (a realm can consist of up to 253 servers).
The emphasis of the Coda development appears to be on moving from a very good research project to a filesystem ready for production use.