Quality of service modeling for green scheduling in Clouds

Best known Cloud providers propose services under constraints of Service Level Agreement (SLA) definitions. The SLAs are composed of different Quality of Service (QoS) rules promised by the provider. Thus, the QoS in Clouds becomes more and more important. Precise definitions and metrics have to be explained. This article proposes an overview of Cloud QoS parameters as well as their classification, but also it defines usable metrics to evaluate QoS parameters. Moreover, the defined QoS metrics are measurable and reusable in any scheduling approach for Clouds. Energy consumption is an inherent objective in Cloud Computing, thus, it is also considered. For evaluation purposes, two uncommon QoS parameters: Dynamism and Robustness are taken into account in different Cloud virtual machines scheduling approaches. Validation is done through comparison of common scheduling algorithms, including a genetic algorithm (GA), in terms of QoS parameters evolution in time. Simulation results have shown that including various QoS parameters allows a deeper scheduling algorithms analysis.