ROLL-FORWARD AND ROLLBACK RECOVERY - PERFORMANCE-RELIABILITY TRADE-OFF

Performance and reliability trade-offs depend on the recovery scheme u sed in any fault-tolerant system. Gain in performance, using comparabl e resources, typically requires sacrifice in reliability, and vice-ver sa. Roll-forward schemes for duplex systems achieve better performance than rollback schemes, without a significant increase in hardware res ource requirements. This paper compares two roll-forward schemes with two roll-back schemes. It is shown that the roll-forward schemes impro ve performance with only a small loss in reliability as compared to ro llback schemes.