Analytic Performance Modeling and Optimization of Live VM Migration

Earlier virtual machine (VM) migration techniques consisted of stop-and-copy: the VM was stopped, its address space was copied to a different physical machine, and the VM was restarted at that machine. Recent VM hypervisors support live VM migration, which allows pages to be copied while the VM is running. If any copied page is dirtied (i.e., modified), it has to be copied again. The process stops when a fraction α of the pages need to be copied. Then, the VM is stopped and the remaining pages are copied. This paper derives a model to compute the downtime, total number of pages copied, and network utilization due to VM migration, as a function of α and other parameters under uniform and non-uniform dirtying rates. The paper also presents a non-linear optimization model to find the value of α that minimizes the downtime subject to network utilization constraints.