A Hybrid Approach to Live Migration of Virtual Machines

Abstract

We present, discuss and evaluate a hybrid approach of live migrating a virtual machine across hosts in a Gigabit LAN. Our hybrid approach takes the best of both the traditional methods of live migration - pre and post-copy. In pre-copy, the cpu state and memory is transferred before spawning the VM on destination host whereas the latter is exactly opposite and spawns the VM on destination right after transferring processor state. In our approach, in addition to processor state, we bundle a lot of useful state information. This includes devices and frequently accessed pages of the VM, aka the working set. This drastically reduces the number of page faults over network while we actively transfer memory. Additionally, on every page fault over the network we transfer a set of pages in its locality in addition to the page itself. We propose a prototype design on KVM/Qemu and present a comparative analysis of pre-copy, post-copy and our hybrid approach.