Granularity and semantic level of replication in the Echo distributed file system

The choices for semantic level and granularity that have been made in the Echo distributed file system are examined. The primary goals of Echo are to explore issues of scaling, availability, and performance. For scaling and uniformity of access, Echo provides a global, hierarchical name space. Replication is used for availability. Performance is achieved by distributed caching on clients and by using a log on the file server to reduce disk seeks. The log also records information about updates that are in progress, and this information is used during crash recovery to bring all replicas into agreement. The Echo hierarchical name space is structured as a collection of subtrees, called echo volumes, that are glued together to form a single name space. Each echo volume may be implemented by a different service, for example, a name service or a file service. The file service component of Echo is discussed