Optimizing Live Migration for Virtual Desktop Clouds

Live migration of virtual machines (VM) from one physical host to another is a key enabler for virtual desktop clouds (VDC). The prevalent algorithm, pre-copy, suffers from long migration times and a high data transfer volume for non-idle VMs which hinders effective use of live migration in VDC environments. In this paper, we present an optimization to the pre-copy method which is able to cut the total migration time in half. The key idea is to load memory pages duplicated on non-volatile storage directly and in parallel from the attached storage device. To keep the downtime short, outstanding data is fetched by a background process after the VM has been restarted on the target host. The proposed method has been implemented in the Xen hyper visor. A thorough performance analysis of the technique demonstrates that the proposed method significantly improves the performance of live migration: the total migration time is reduced up to 90% for certain benchmarks and by 50% on average at an equal or shorter downtime of the migrated VM with no or only minimal side-effects on co-located VMs.