KLAT2's Flat Neighborhood Network

KLAT2, Kentucky Linux Athlon Testbed 2, is a cluster of 64 (plus two ``hot spare'') 700MHz AMD Athlon PCs. The raw compute speed of the processors justifies calling the system a supercomputer, but these fast nodes must be mated with a high-performance network in order to achieve the balance needed to obtain speed-up on real applications. Usually, cluster networks are built by combining the fastest available NICs and switching fabric, making the network expensive. Instead, KLAT2 uses a novel ``Flat Neighborhood'' network topology that was designed by a genetic algorithm (GA). A total of about $8,100 worth of 100Mb/s Fast Ethernet NICs, switches, and Cat5 cable, allows KLAT2's network to deliver both single-switch latency for any point-to-point communication and up to 25.6Gb/s bisection bandwidth. This paper describes how this new network architecture was derived, how it is used, and how it performs.