Replication is key to achieving performance and fault tolerance in widely distributed systems. Conservative replica management schemes do not scale well, yet optimistic approaches depend in complex ways on workload, architecture, topology, and failure modes of the system. This research captures the design space for optimistically replicated systems in a flexible, object-oriented, simulation model, allowing alternative architectures to be evaluated on a `level playing field.` The object-oriented nature allows specialization of model components, permitting experimentation with alternative designs, communications bandwidths, failure distributions, workload models, etc. A flexible workload generation tool which can be tuned to produce synthetic traces matching the statistical properties of various anticipated environments is also produced. The simulation and synthetic trace generator are validated by comparison with analytical models and measurements of real systems. This reqearch will enable designers of a broad range of distributed database and filing systems to assess the impact of an optimistic app roach to achieving high performance and availability in large scale systems. The educational plan seeks to add a `hands-on`, experimental component to the operating systems curriculum. Synchronization, scheduling, and concurrency control simulation labs are constructed and piloted using the same object-oriented simulation methodology as in the research plan. This provides a balance to the current theoretical approach to teaching operating systems to both undergraduate and graduate students.
