PRACTI Replication for Large-Scale Systems

Many replication mechanisms for large scale distributed systems exist, but they require a designer to compromise a system’s replication policy (e.g., by requiring full replication of all data to all nodes), consistency policy (e.g., by supporting per-object coherence but not multiobject consistency), or topology policy (e.g., by assuming a hierarchical organization of nodes.) In this paper, we present the first PRACTI (Partial Replication, Arbitrary Consistency, and Topology Independence) mechanisms for replication in large scale systems. These new mechanisms allow construction of systems that replicate or cache any data on any node, that provide a broad range of consistency and coherence guarantees, and that permit any node to communicate with any other node at any time. Our evaluation of a prototype suggests that by disentangling mechanism from policy, PRACTI replication enables better trade-offs for system designers than possible with existing mechanisms. For example, for one workload we study, PRACTI’s partial replication reduces bandwidth requirements by over an order of magnitude compared to full replication for nodes that only care about a subset of the system’s data.