Using group communication to implement a fault-tolerant directory service

Group communication is an important paradigm for building distributed applications. The authors discuss a fault-tolerant distributed directory service based on group communication, and compare it with the previous design and implementation based on remote procedure call (RPC). The group directory service uses an active replication scheme and, when triplicated, can handle 627 lookup operations per second and 88 update operations per second (using nonvolatile RAM). This performance is better than the performance for the RPC implementation and it is even better than the performance for directory operations under SunOS, which does not provide any fault tolerance at all. The conclusion is that the implementation using group communication is simpler and has better performance than the one based on remote procedure call, supporting the claim that a distributed operating system should provide both remote procedure call and group communication