Hybrid Cloud Management to Comply Efficiently with SLA Availability Guarantees

SLAs are common means to define specifications and requirements of cloud computing services, where the guaranteed availability is one of the most important parameters. Fulfilling the stipulated availability may be expensive, due to the cost of failure recovery software, and the amount of physical equipment needed to deploy the cloud services. Therefore, a relevant question for cloud providers is: How to guarantee the SLA availability in a cost efficient way? This paper studies different fault tolerance techniques available in the market, and it proposes the use of an hybrid management to have full control over the SLA risk, using only the necessary resources in order to keep a cost efficient operation. This paper shows how to model the probability distribution of the accumulated downtime, and how this can be used in the design of hybrid policies. Using specific case studies, this paper illustrates how to implement the proposed hybrid policies, and it shows the obtained cost saving by using them. This paper takes advantage of the cloud computing flexibility, and it opens the door to the use of dynamic management policies to reach specific performance objectives in ICT systems.