Adaptive load sharing in heterogeneous systems

The performance characteristics of simple load-sharing algorithms are studied for heterogeneous distributed systems. It is assumed that non-negligible delays are encountered in transforming jobs from one node to another and in gathering remote state information. The effects of these delays on the performance of two algorithms called Forward and Reverse are analyzed. Queuing theoretic models are formulated for each of the algorithms operating in heterogeneous systems under the assumption that the job arrival process at each node is Poisson and the service times and job transfer time are exponentially distributed. The models are solved using the matrix-geometric solution technique. The models are tested with regard to the effects of varying thresholds, the impact of changing the probe limit, and the determination of the optimal response times over a large range of loads and delays. Wherever relevant, the results of the models are compared with M/M/1, random assignment, and the M/M/K models.<>