Performance Evaluation of HARP: a Hierarchical Asynchronous Replication Protocol for Large Scale Systems

This report evaluates the performance of HARP, a hierarchical replication protocol based on nodes organised into a logical hierarchy. The scheme is based on communication with nearby replicas and scales well for thousands of replicas. It proposes a new service interface that provides different levels of asynchrony, allowing strong consistency and weak consistency to be integrated into the same framework. Further, it provides the ability to ooer diierent levels of staleness, by querying from diierent levels of the hierarchy. We present results from a detailed simulation analysis evaluating the beneets and losses in performance resulting from using synchronous versus asynchronous operations within HARP under diierent system conngurations and load mixes. Further, the performance is evaluated on diierent network topologies. An analytical solution based on the Open Queueing Network Model with Multiple Job Classes is carried out for the veriication of the simulation model and the results are presented.