Fault Tolerance Directed by Service Level Agreement in Cloud Computing Environments

The CloudComputing environments are susceptible to frequent failures as a result of theirdynamic and unstable nature. Failures have a significant effect on cloudperformance and on the benefits that customers and providers expect. Therefore,fault tolerance is necessary to mitigate the impact of failures and preventingrevenue losses due to service level agreements (SLA) violation penalties. Inthis paper, we propose a fault tolerance directed by the SLA contractsestablished between cloud providers and customers. The proposed fault toleranceincludes two phases, the first is based on the use of idles VMs according toselection strategies. The second phase is based on both advanced operation ofdegradation of quality of service and on VMs selection strategies. The advancedoperation of degradation consists of beneficial combinations of VMs deallocationand allocation between customers leading to avoid SLA violation penalties.According to the experimental results, our proposed fault tolerance decreasesthe considered SLA violations