State-of-the-Practice in Data Center Virtualization: Toward a Better Understanding of VM Usage

Hardware virtualization is the prevalent way to share data centers among different tenants. In this paper we present a large scale workload characterization study that aims to a better understanding of the state-of-the-practice, i.e., how data centers in the private cloud are used by their customers, how physical resources are shared among different tenants using virtualization, and how virtualization technologies are actually employed. Our study focuses on all corporate data centers of a major infrastructure provider that are geographically dispersed across the entire globe and reports on their observed usage across a 19-day period. We especially focus on how virtual machines are deployed across different physical resources with an emphasis on processors and memory, focusing on resource sharing and usage of physical resources, virtual machine life cycles, and migration patterns and frequencies. Our study illustrates that there is a huge tendency in over provisioning resources while being conservative to the several possibilities opened up by virtualization (e.g., migration and co-location), showing tremendous potential for the development of policies aiming to reduce data center operational costs.