Scalability analysis in gracefully-degradable large systems

• Published in: IEEE transactions on reliability Vol. 40; no. 2; pp. 189 - 197
• Main Authors: Najjar, W.A., Gaudiot, J.-L.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.06.1991; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Availability; Computer networks; Degradation; Electronics; Exact sciences and technology; Hardware; Performance analysis; Performance evaluation; Power system reliability; Redundancy; Reliability; Reliability theory; Scalability; Time measurement; Degradation; Multiprocessor; Scale effect; Reliability; Performance; Fault tolerant system; Large scale system
• ISSN: 0018-9529; 1558-1721
• DOI: 10.1109/24.87126

The scalability of large degradable homogeneous multiprocessors is analyzed. The objective is to assess the limitations, imposed by reliability considerations, on the number of processors. The analysis of the mean-time-to-failure and the mission-time shows that, for a given value of the coverage factor, there exists a value of the number of processors at which these measures are maximal. As the system size is increased beyond this value, the reliability of the system becomes a rapidly decreasing function of the number of processors. For computations with linear speed-up, the amount of reliable computational work is constant for large system-sizes. When the speed-up is not linear, this amount is a decreasing function of the number of processors. Therefore, for large system-sizes and same technology, increasing the number of processors results in a decrease of the average amount of reliable computational work the system can deliver. Graceful degradation in large fault-tolerant systems is not scalable.< >