Leili Salimian - Islamic Azad University Najafabad Branch,
Faramarz Safi - Faculty of computer Islamic Azad University of Najafabad,

The rapid growing demand for computational power by modern applications in Cloud Computing has led to the creation of large-scale data centers. Such data centers consume huge amount of electrical energy, emitting a great deal of CO2 in our environment. One effective way so as to reduce energy consumption is consolidating the vms using dynamic migration on minimum number of nodes and switching idle nodes to the sleep or hibernate modes which can cause better resource usage. But, due to the varying workloads in applications, consolidating the vms can cause SLA violation specially in cases that resource usage exceeds upper threshold defined for such nodes including consolidated vms. On the one hand, due to the necessity of providing the high QoS for customers which is negotiated in terms of SLA in cloud computing and on the other hand, importance of energy consumption as a critical problem, there is the necessity in addressing performance-energy trade off - the minimization of energy consumption, at the same time to take into account QoS. In this paper, related works regarding energy efficient datacentres have been conducted and in the end they have been compared with each other

Cloud computing, Data center, Energy Efficiency, Consolidating of VMs