Models for Dependability Analysis of Cloud Computing Architectures for Eucalyptus Platform

High availability in cloud computing services is essential for maintaining customer confidence and avoiding revenue losses due to SLA violation penalties. Since the software and hardware components of cloud infrastructures may have limited reliability, fault tolerance mechanisms are means of achieving the necessary dependability requirements. This paper investigates the benefits of a warm-standy replication mechanism in three architectures based on Eucalyptus cloud computing as well as the required acquisition cost. A heterogeneous hierarchical modeling approach is used to represent the redundancy strategy and to compare the availability for the architectures presented. Both hardware and software failures are considered in the proposed analytical models. The results highlight the improvements on the availability for the redundant architectures, the respective impact on the annual downtime and the related respective costs.