It's a cluster, made out of commodity computers and network equipment, that wasn't designed specifically to be part of a cluster. "Beowulf" was just the name o

It's a cluster, made out of commodity computers and network equipment, that wasn't designed specifically to be part of a cluster. "Beowulf" was just the name of an early machine built that way at NASA in the 90s. The approach is not unusual now; many "low-end" supercomputers are just a few racks of commodity servers. But it was very unconventional in the early 90s, which is why the Beowulf term existed, to distinguish it from "real" clusters. Hardware Ethernet switches -- able to stream from port to port at full speed -- were the revolutionary component. Before Ethernet, clusters required specialized hardware implementing a crossbar-like switched fabric, so that all the nodes could communicate at high speed with each other, with a minimum of hops. These were solutions for clustering mainframes and minicomputers, horribly expensive and proprietary.