By Josh Simons on Jun 19, 2008
Here is a quick look under the covers of the new Sun Datacenter Switch 3x24, the new InfiniBand switch just announced by Sun at ISC 2008 in Dresden. First some photos and then an explanation of how this switch is used as a Sun Constellation System component to build clusters with up to 288 nodes.
First, the photos:
You might assume NanoMagnum is either a simple 24-port InfiniBand switch or, if you know that each connector actually carries three separate InfiniBand 4X connections, a simple 72-port switch. In fact, it is neither. NanoMagnum is a core switch and none of the three InfiniBand switch chips is connected to the others. Since it isn't intuitive how a box containing three unconnected switch chips can be used to create single, fully-connected clusters, let's look in detail at how this is done. I've created two diagrams that I hope will make the wiring configurations clear.
Before getting into cluster details, I should explain that a NEM, or Network Express Module, is an assembly that plugs into the back of each of the four shelves in a Sun Blade 6048 chassis. In the case of an InfiniBand NEM, it contains the InfiniBand HCA logic needed for each blade as well as two InfiniBand leaf switch elements that are used to tie the shelves into cluster configurations. You can see a photo of a NEM above.
The first diagram (below) illustrates how any blade in a shelf can reach any blade in any other shelf connected to a NanoMagnum switch. There are a few important points to note. First, all three switch chips in the NanoMagnum are connected to every switch port, which means that regardless of which switch chip your signal enters, it can be routed to any other port in the switch. Second, you will notice that only one switch chip in the NEM is being used. The second is used only for creating redundant configurations and the cool thing about that is that from an incremental cost perspective, one need only buy additional cables and additional switches--the leaf switching elements are already included in the configuration.
If the above convinced you that any blade can reach any other blade connected to the same switch, the rest is easy. The diagram below shows the components and connections needed to build a 288-node Sun Constellation System using four NanoMagnums.
Clusters of smaller size can be built in a similar way, as can clusters that are over-subscribed (i.e. not non-blocking.)