The cost of reconfiguration in a cloud.

ABSTRACTEmerging clouds promise enterprises the ability to increase or decrease their resource allocation on demand using virtual machine resizing and migration. These dynamic reconfiguration actions lead to performance impact during the reconfiguration duration. In this paper, we study the cost of reconfiguring a cloud-based IT infrastructure in response to workload variations. We observe that live migration requires a significant amount of spare CPU on the source server (but not on the target server). If spare CPU is not available, it impacts both the duration of migration and the performance of the application being migrated. Further, the amount of CPU required for live migration varies with the active memory of the VM being migrated. Finally, we show that live migration may impact any co-located VMs based on the cache usage pattern of the co-located VM. We distill all our observations to present a list of practical recommendations to cloud providers for minimizing the impact of reconfiguration during dynamic resource allocation.