Techniques for Building Highly Available Distributed File Systems

This paper analyzes recent research in the field of distributed file systems, with a particular emphasis on the problem of high availability. Several of the techniques involved in building such a system are discussed individually: naming, replication, multiple versions, caching, stashing, and logging. These techniques range from extensions of ideas used in centralized file systems, through new notions already in use, to radical ideas that have not yet been implemented. A number of working and proposed systems are described in conjunction with the analysis of each technique. The paper concludes that a low degree of replication, a liberal use of client and server caching, and optimistic behavior in the face of network failure are all necessary to ensure high availability.