Virtual Performance Won't Do: Capacity Planning for Virtual Systems

The history of computing is a history of virtualization. Each increase in the number of abstraction layers separating the end user from the hardware makes life easier for the user but harder for the system capacity planner who must understand the relationship between logical and physical configurations to guarantee performance. In this paper we discuss possible architectures for virtual systems and show how naïve interpretations of traditional metrics like “utilization” may lead planners astray. Then we propose some simple generic prediction guidelines that can help planners manage those systems. We close with a benchmark study that reveals a part of the architecture of VMware.