Analysis of the effects of delays on load sharing

The authors study the performance characteristics of simple load-sharing algorithms for distributed systems. In the systems under consideration, it is assumed that nonnegligible delays are encountered in transferring tasks from one node to another and in gathering remote state information. Because of these delays, the state information gathered by the load-sharing algorithms is out of date by the time the load-sharing decisions are taken. The authors analyze the effects of these delays on the performance of three algorithms, called forward, reverse, and symmetric. They formulate queueing-theoretic models for each of the algorithms operating in a homogeneous system under the assumption that the task arrival process at each node is Poisson and the service times and task transfer times are exponentially distributed. Each of the models is solved using the matrix-geometric solution technique, and the important performance metrics are derived and studied