Application-Managed Database Replication on Virtualized Cloud Environments

One among several patterns that are common for applications being deployed in cloud platforms is to take an existing application designed for a conventional data center, and then port it to the cloud with minimal changes. When this is done, the application tier can easily take advantage of the elasticity and scale provided by the cloud, but the data management layer, being stateful, faces more issues. In this paper, we explore experimentally the limits to scaling for an application that itself manages database replicas each placed in a virtual machine in the cloud (exactly following the design used when the application would be deployed on an in-house cluster). We characterize important limits in the load on the master copy, the workload imposed on each slave copy when processing updates from the master, and also from the increasing staleness of replicas.