T. Kashiwagi, M. Suetake , K. Kourai (Kyushu Institute of Technology) Migration of Virtual Machines Running across 　Multiple Hosts T. Kashiwagi, M. Suetake , K. Kourai (Kyushu Institute of Technology) Background Host 1 Host 2 IaaS clouds provide virtual machines (VMs) with a large amount of memory E.g., Amazon EC2 provides VMs with 4TB memory Migrating large-memory VMs is difficult VM migration needs sufficient free memory at the destination host VM VM memory memory migrate Issues Split Migration [Suetake et al.’18] Migrate one VM to multiple hosts Main host : VM’s core and memory likely to be accessed Sub-hosts : Rest of the memory Run it as split-memory VM Exchange memory data between multiple hosts with remote paging Issue 1: Remote paging causes performance degradation Up to 70% for in-memory DB Issue 2: Maintenance of several hosts needs to stop the entire VM 　　　Main host VM memory Host 1 Main host migrate VM VM Memory 2TB memory 1TB memory memory 1TB 　　Sub-host Sub-host Unified Migration Partial Migration Merge a VM across multiple hosts into one host again Acceleration by parallel transfer of memory data Improve memory access performance No remote paging Migrate only part of a split-memory VM Main host only, sub-host only, etc. Enable maintaining several hosts Without stopping the VM Main host 1 Main host 2 Main host Host VM migrate VM memory memory メモリ migrate メモリ VM memory VM memory remote paging memory memory Sub-host Sub-host Experimental Results migration time throughput Unified migration was 2x faster than traditional one Thanks to parallel transfer The performance of in-memory DB was improved by 11% Compared with before unified migration