Redundancy for Highly Available Systems - Design and Analysis

Availability is a key aspect during the design and operation of industrial automation systems. Failures not only result in unanticipated problems but also often cause high costs. Therefore redundancy is often applied in industrial applications and systems. Drawing on hierarchically structured design elements, this article provides guidelines for requirement elicitation as well as for decision support and design of a suitable redundancy pattern. This allows for a well-directed and informed redundancy design as well as efficient and effective redundancy implementation according to system specific requirements. Furthermore, an overview is presented of implementation alternatives for software-based standby redundancy, with an analytical evaluation and comparison of these techniques. Guidelines are derived for selecting an appropriate alternative.