Amdahl's Law of Data Compression for Live Migration of Virtual Machines

Abstract

Data compression is usually perceived as a mean to help improve performance of live migration of Virtual Machines (VM). However, such perception may be wrong since there are many factors involved in the combination of live migration and data compression. This paper presents a novel performance model to describe the speedup of VM live migration when used in combination with data compression mechanisms, namely the Amdahl's Law of data compression for live migration of VMs. The speedup is calculated by dividing the total live migration time when the migration is performed in combination with data compression by that without data compression. This model introduces live migration bandwidth as a new factor in the speedup calculation. The live migration bandwidth is the data transmission rate of a live migration mechanism. According to our model, the speedup of live migration using data compression would approach zero as the live migration bandwidth increases toward infinity. A set of theorems derived from the model are presented. A number of experiments have been conducted to confirm these theorems. In the experiments, QEMU-KVM's pre-copy live migration is used to migrate VMs running several memory-intensive OpenMP NAS Parallel benchmarks with and without data compression. Live migrations are performed over 100 Mbps and 1 Gbps networks. Experimental results confirm the validity of the proposed Amdahl's Law of data compression model.