Fujitsu Laboratories has developed a technology that reduces the number of network switches used in a cluster supercomputer by 40%.
Instead of using a conventional, "fat tree" network topology, in which, for example, 6,000 servers would require about 800 switches, or possibly more than 2,000 switches, Fujitsu Labs is using a multi-layer full mesh topology in combination with a newly developed communications algorithm that controls transmission sequences to avoid data collisions.
Fujitsu said its approach can accommodate a large number of servers with relatively few switches by considering what would be an optimized data-exchange process, then connecting the cluster in a new way. By using scheduling, servers connected to the various apex switches (A through F) will divert to a different apex, and also by avoid collisions within paths that traverse different layers (a1 through d3).
http://www.fujitsu.com/global/about/resources/news/press-releases/2014/0715-02.html
