The first (that I know of) Xserve cluster, done by our friends at NASA:
http://daugerresearch.com/fractaldemos/JPLXServes/JPLXServeClusterBenchmark.html
P.S - Don't forget ot look at the link at the bottom comparing this 33 node cluster to the 76 node cluster of older powermacs - very impressive!
http://daugerresearch.com/fractaldemos/JPLXServes/JPLXServeClusterBenchmark.html
P.S - Don't forget ot look at the link at the bottom comparing this 33 node cluster to the 76 node cluster of older powermacs - very impressive!