Availability analysis for the design of distributed processing networks
This paper presents an analytical model for evaluating the availability of distributed processing systems. The model, which is based on a well-known probability formula, has been implemented in FORTRAN and used for the design of a real-time distributed processing system that requires high availability. It is applied to a sample distributed processing system to illustrate its usefulness and to provide good insight into the design of highly available distributed processing systems. Effects of homogeneous/heterogeneous clustering and standby spare are illustrated. The concept of availability threshold where the distributed system may gain or lose availability over the individual processor availability is introduced. It has proven to be a valuable tool for the tradeoffs in the allocation of system requirements. The concluding remarks summarize the lessons learned and suggest cost-effective ways to achieve higher availability for the design of distributed processing systems.