Performance of Dynamic Replication Schemes for an Internet Hosting Service

The paper explores schemes for dynamic replication and migration of web objects in the context of an Internet hosting service. It describes a replica placement algorithm for deciding the location and number of replicas of an object as well as request distribution schemes for choosing among currently available replicas. We compare two classes of request distribution algorithms – namely feedback and non-feedback based. Further, we compare dynamic replication to a static replication scheme. We have simulated the algorithms using synthetic workloads as well as a real trace from a hosting service. Measurement and analysis show that dynamic replication significantly reduces bandwidth consumption and latency, removes hot spots from the network and smooths out bursts in bandwidth demand while imposing only a low network traffic overhead. For example, on the trace, our algorithm reduces bandwidth consumption by as much as 52%while imposing a traffic overhead of only about 5%. Results of the simulation also demonstrate that at high loads, the ability to predict the effect of a migration or replication is important for any system that takes dynamic replica placement decisions.