Optimizing Live Migration of Multiple Virtual Machines

The Cloud computing paradigm is enabling innovative and disruptive services by allowing enterprises to lease computing, storage and network resources from physical infrastructure owners. This shift in infrastructure management responsibility has brought new revenue models and new challenges to Cloud providers. One of those challenges is to efficiently migrate multiple virtual machines (VMs) within the hosting infrastructure with minimum service interruptions. In this paper we first present a live-migration performance testing, captured on a production-level Linux-based virtualization platform, that motivates the need for a better multi-VM migration strategy. We then propose a geometric programming model whose goal is to optimize the bit rate allocation for the live-migration of multiple VMs and minimize the total migration time, defined as a tradeoff cost function between user-perceived downtime and resource utilization time. By solving our geometric program we gained qualitative and quantitative insights on the design of more efficient solutions for multi-VM live migrations. We found that merely few transferring rounds of dirty memory pages are enough to significantly lower the total migration time. We also demonstrated that, under realistic settings, the proposed method converges sharply to an optimal bit rate assignment, making our approach a viable solution for improving current live-migration implementations.