Optimal reconfiguration strategy for a degradable multimodule computing system

A new quantitative approach to the problem of reconfiguring a degradable multimodule system is presented. The approach is concerned with both assigning some modules for computation and arranging others for reliability. Conventionally, a fault-tolerant system performs reconfiguration only upon a subsystem failure. Since there exists an inherent trade-off between the computation capacity and fault tolerance of a multimodule computing system, the conventional approach is a passive action and does not yield a configuration that provides an optimal compromise for the trade-off. By using the expected total reward as the optimal criterion, the need and existence of an active reconfiguration strategy, in which the system reconfigures itself on the basis of not only the occurrence of a failure but also the progression of the mission, are shown. Following the problem formulation, some important properties of an optimal reconfiguration strategy, which specify (i) the times at which the system should undergo reconfiguration and (ii) the configurations to which the system should change, are investigated. Then, the optimal reconfiguration problem is converted to integer nonlinear knapsack and fractional programming problems. The algorithms for solving these problems and a demonstrative example are given. Extensions of the optimal reconfiguration problem are also discussed.