Server Consolidation in Cloud Computing

Minimizing service-level agreement (SLA) violations and energy consumption through server consolidation is of paramount importance for the sustainability of cloud environments. In this paper, we propose an online method to reduce cloud SLA violations by taking into account: (a) the energy consumption of migrating virtual machines and (b) server consolidation techniques to minimize the energy consumption within the system. Rigorous mathematical competitive analysis shows that the proposed method achieves a 2.4 competitive ratio against a cognitive adversary. Our solution is superior compared to the current state of the art algorithms, such as UP-VMC, KMI, MBFD, both theoretically (competitive ratios of other alternatives are unbounded) and empirically through simulations using CloudSim. More specifically, the competitive ratios of state of the art algorithms are unbounded and our proposed methodology reduces the VM migrations and energy consumption by 85% and 45%, respectively. The aforementioned improvement comes at an expense of a small increase in terms of SLA violations. The above results are achieved without the a priori knowledge of VM utilization patterns.