Effects of Dynamic Cloud Cluster Load on Differentiated Service Availability.

Accredited to the diverse nature of cloud services, there is a need for cloud providers to offer differentiated availability for different service types in their SLAs. This can be achieved by using different redundancy strategies and fault-tolerance techniques. The availability resulting from these techniques is highly dependent upon the load on cloud datacenters and their clusters. This load is dynamic, caused by both variations in demand and failures in servers, network, and other cloud infrastructure. In this paper, the effect of dynamic load in a cloud cluster on the service availability is studied, using analytical models and simulations. The results are thus obtained for different loads and compared among different service classes. The analytical models are not able to grasp the interaction between different classes, and hence a simulation is performed. The results show that the cluster load has a quantifiable effect on service availability, and it increases with decreasing level of priority assigned to a service class.