Fuzzy control of sparing in disk arrays

The redundancy regeneration (sparing or rebuild) algorithms in disk arrays face the problem of balancing between the data recovery activity within the array and the user workload acting upon the array at the same time [1]. If the algorithm favors the user workload so the user requests can always preempt the internal data recovery, then the data sparing can stall in the presence of a sustained workload. But on the contrary, if the data recovery is favored over the user requests, the latency of the user requests can be so high to reach unacceptable levels for the data transactions. Using computationally intelligent techniques, like fuzzy logic, better algorithms to balance the level of user requests and the internal data recovery can be achieved. The disk array and data recovery process are modeled using the queue systems with vacations (QSV) [2]. A fuzzy algorithm to control the sparing is presented in this paper. The results indicate that by using fuzzy logic, a better balancing is achieved between the need to have an acceptable response time for the user requests and the data recovered as soon as possible.