Containing the Hype

Containers, or OS-based virtualization, have seen a recent resurgence in deployment. The term "container" is nearly synonymous with "lightweight virtualization", despite a remarkable dearth of careful measurements supporting this notion. This paper contributes comparative measurements and analysis of both containers and hardware virtual machines where the functionality of both technologies intersects. This paper focuses on two important issues for cloud computing: density (guests per physical host) and start-up latency (for responding to load spikes). We conclude that the overall density is highly dependent on the most demanded resource. In many dimensions there are no significant differences, and in other dimensions VMs have significantly higher overheads. A particular contribution is the first detailed analysis of the biggest difference---memory footprint---and opportunities to significantly reduce this overhead.