SAHAYOG: A test bed for evaluating dynamic load-sharing policies

This paper describes the implementation of a test bed called SAHAYOG, for evaluating dynamic load-sharing policies in which job-transfer decisions are based on the state of the system. The test bed is implemented on a network of AT&T 3B2 minicomputers. It provides an interactive user interface for conducting load-sharing experiments. Based on user-specified parameters it creates independent job streams at different nodes in the network. Jobs are transferred among the nodes by the load-sharing algorithm being evaluated. Each node collects data about the jobs, which are used to generate statistics about the experiment. Five load-sharing algorithms are implemented and evaluated using the test bed under different load conditions and for various parameter values. These experiments confirm some earlier results about load sharing and also provide some new insights. SAHAYOG also contains an optional fault-tolerance feature to handle single-node failures, and evaluates the effect of fault tolerance on the performance of different policies.