Load Balancing Schemes for High-Throughput Distributed Fault-TolerantServers

Clusters of workstations, connected by a fast network, are emerging as a viable architecture for building high-throughput fault-tolerant servers. This type of architecture is more scaleable and more cost-effective than a tightly coupled multiprocessor and may achieve as good a throughput. Two of the most important issues that a designer of such clustered servers must consider in order for the system to meet its fault-tolerance and throughput goals are the load balancing scheme and the fault-tolerance scheme that the system will use. This paper explores several combinations of such fault tolerance and load-balancing schemes, and compare their impact on the maximum throughout achievable by the system, and on its survivability. In particular, we show that a fault-tolerance scheme may have an effect on the throughput of the system, while a load-balancing scheme may affect the ability of the system to override failures. We study the scaleability of the different schemes under different loads and failure conditions. The validation of our schemes is done using data taken from emulations of an intelligent networking coprocessor of a telephone switch, which follows, for example, the SS7 signaling protocol