System management to comply with SLA availability guarantees in cloud computing

SLAs are common means to define specifications and requirements of cloud computing services in business relationships. The terms that define the guaranteed availability for a given period are fundamental to these contracts. In this context, a natural question for cloud providers is: How to guarantee the availability promised? This paper studies the level of availability offered to a virtual machine during an SLA period in clouds with different: size, redundancy, and fault tolerance techniques. Finally, this paper proposes the use of the SLA -budget for the implementation of smart policies in: i) the assignment of spare servers when virtual machines are restored. ii) the dynamic use of different fault tolerance licenses. Using such policies results in a considerable reduction of the probability of breaching the SLA guarantee, by making an efficient use of the cloud resources available. This paper is a first step in the design of SLA-aware cloud architectures.