Application Redundancy and Cloud Computing

This chapter considers how simplex, traditional (sequential) redundancy and nontraditional (concurrent) redundancy architectures mitigate the application service impacts of virtualized infrastructure impairments. It explains how virtualization technology can improve software restore times, and how virtualization and cloud computing can improve infrastructure restore times. Next, the chapter compares and contrasts sequential redundancy with concurrent redundancy arrangements. It then methodically considers the application service impact of virtualized infrastructure impairments on simplex, sequential redundant, concurrent redundant, and hybrid concurrent redundant architectures. The chapter also explains traditional hardware repair, automatic VM Repair-as-a-Service (RaaS), and discusses the implications of these mechanisms. Finally, the chapter summarizes the advantages and drawbacks of the four redundancy architectures across several dimensions: service quality impact; concurrency control; resource usage; and simplicity.