Fast Live Migration with Small IO Performance Penalty by Exploiting SAN in Parallel

Virtualization techniques greatly benefit cloud computing. Live migration enables a datacenter to dynamically replace virtual machines (VMs) without disrupting services running on them. Efficient live migration is the key to improve the energy efficiency and resource utilization of a datacenter through dynamic placement of VMs. Recent studies have achieved efficient live migration by deleting the page cache of the guest OS to shrink the memory size of it before a migration. However, these studies do not solve the problem of IO performance penalty after a migration due to the loss of page cache. We propose an advanced memory transfer mechanism for live migration, which skips transferring the page cache to shorten total migration time while restoring it transparently from the guest OS via the SAN to prevent IO performance penalty. To start a migration, our mechanism collects the mapping information between page cache and disk blocks. During a migration, the source host skips transferring the page cache but transfers other memory content, while the destination host transfers the same data as the page cache from the disk blocks via the SAN. Experiments with web server and database workloads showed that our mechanism reduced total migration time with significantly small IO performance penalty.