Although many algorithms and implementations of replicated services have been developed, most have embedded aspects of the replication management in the invocation protocol. This makes it extremely difficult to modify the replication protocol without changing the protocol used by the clients, and causes an undesirable violation of both transparency and modularity. The GRIP protocol supports the fault-tolerant remote invocation of replicated services, providing not only the usual location transparency but also transparency of replication semantics. Our approach is independent of the details of the replica control protocol used to maintain the consistency of server replicas. We use a lightweight remote invocation protocol in order to minimize the impact on the client of issues such as scale and replication consistency maintenance. Furthermore, unlike most previous systems we provide explicit support for weakly consistent replication protocols. GRIP is designed as a collection of modular services, which can be configured according to the needs of the application.>

The design and implementation of Coda, a file system for a large-scale distributed computing environment composed of Unix workstations, is described. It provides resiliency to server and network failures through the use of two distinct but complementary mechanisms. One mechanism, server replication, stores copies of a file at multiple servers. The other mechanism, disconnected operation, is a mode of execution in which a caching site temporarily assumes the role of a replication site. The design of Coda optimizes for availability and performance and strives to provide the highest degree of consistency attainable in the light of these objectives. Measurements from a prototype show that the performance cost of providing high availability in Coda is reasonable.>

The evolution of MultiRPC, a parallel remote procedure call mechanism implemented in Unix is described. Parallelism is obtained from the concurrency of processing on servers and from the overlapping of retransmissions and timeouts. Each of the parallel calls retains the semantics and functionality of the standard remote procedure calls. The underlying communication medium need not support multicast or broadcast transmissions. An analytic model of the system is derived and validated. The experimental observations demonstrate the feasibility of using MultiRPC to contact up to 100 servers in parallel.>