D3: discarding dispensable data for efficient live migration of virtual machines

Virtualization, one of the most actively adopted technologies today in computer systems, is increasingly widening its range of applications. As multiple virtual machines are concurrently executed on a physical machine, they compete for physical resources such as CPU, DRAM, HDD and NIC. In large scale data centers or cluster systems, therefore, it is required to balance each physical machine's load by migrating a virtual machine to another physical machine. Since system performance is significantly hindered during migration, a technique that can reduce the migration overheads is required. Interestingly, we notice that virtual machines' memory contain numerous dispensable data. Therefore, in this paper, we propose an efficient virtual machine migration technique called D3 (Discarding Dispensable Data). The basic idea is simple but effective: finding indispensable page frames, and then, transferring only those page frames. In D3, simple metadata is handed over for the dispensable page frames, instead of actual data transmission, and the discarded page frames are reconstructed appropriately after the migration process. One issue is that checking whether a page frame is dispensable or not based on comparing the entire content yields excessive overhead. To overcome this problem, we devise a novel sampling based dispensable page frame detection technique. D3 have implemented in Xen virtualization software and evaluated on a realistic environment with relevant workloads. We show that D3 can efficiently reduce migration time up to 64.2% and size of memory required for completing a migration up to 94.8%. We also present that D3 is very useful to provide a certain level of QoS and better performance.