Temporal costs of computing unit redundancy in steady and transient state

Abstract

Industrial real-time computer systems are designed to operate with high reliability level. It is most often achieved by the use of redundancy. Additional elements introduced to the system are supposed to make it invulnerable to failures of their redundant components. Implementation of redundancy entails significant extra costs. The financial costs are quite obvious and easy to estimate they are associated with the need to deliver, configure, program, service and maintain additional devices and communication interfaces. There are however another costs which are not so evident because they derive from the system operation and data processing. Those are the temporal costs of redundancy that influence the real-time systems characteristics and in the end may determine the system usability.