Replicated Rejuvenated Services. A Case Study

During testing, verification and validationof complex software it is difficult to detect all faults. Itis hard to anticipate run-time complex interactions inorder to design reactive fault tolerance mechanismscovering all situations. As such, proactive faulttolerance techniques are required. Softwarerejuvenation is a proactive fault tolerance techniquedesign to bring the system to a clear state whendegradation of functionality is detected. As defined atbeginning, software rejuvenation is considered only fora system (an application).Due to increase in quality-of-service requirements, theuser is the part assessing the availability of servicesdelivered. The user does not care about the systemdelivering the service. We defined replicatedrejuvenated services for modeling rejuvenation whenwe consider the availability of the services delivered.The model proposed considers the services delivered by an application, where replication can be used to improve availability.A case study is presented in this paper. The original model for software rejuvenation is compared with the model proposed for replicated rejuvenated services. Cost analysis is presented for both cost of downtime and const of unavailability.