Deceit: a flexible distributed file system

Deceit, a distributed file system that provides flexibility in the fault-tolerance and availability of files, is described. Deceit provides many capabilities to the user: file replication with concurrent reads and writes, a range of update propagation strategies, automatic disk load balancing and the ability to have multiple versions of a file. Deceit provides Sun Network File Server (NFS) protocol compatibility; no change in NFS client software is necessary in order to use Deceit. The purpose of Deceit is to replace large collections of NFS servers. NFS suffers from several problems in an environment where most clients mount most servers. First, if any one server crashes, clients will block or fail when they try to access that server, and, as the number of servers increases, this problem becomes more likely. Second, servers have a (roughly) fixed capacity, yet it is difficult to move files from one NFS server to another without disrupting clients. Third, replicating a file to increase its availability must be managed by the user. Deceit addresses these three problems