Creating Raspberry Pi clusters is a popular hacker activity. Bitscope has been commercializing these clusters for a bit now and last year they created a cluster of 750 Pis for Los Alamos National Labs. You might wonder what an institution know for supercomputers wants with a cluster of Raspberry Pis. Turns out it is tough to justify taking a real high-speed cluster down just to test software. Now developers can run small test programs with a large number of CPU cores without requiring time on the big iron.
On the face of it, this doesn’t sound too hard, but hooking up 750 of anything is going to have its challenges. You have to provide power and carry away heat. They all have to communicate, and you aren’t going to want to house the thing in a few hundred square feet which makes heat and power even more difficult.
The system is modular with each module holding 144 active nodes, 6 spares, and a single cluster manager. This all fits in a 6U rack enclosure. Bitscope points out that you could field 1,000 nodes in 42U and the power draw — including network fabric and cooling — would be about 6 kilowatts. That sounds like a lot, but for a 1,000 node device, that’s pretty economical. The cost isn’t bad, either, running about $150,000 for 1,000 nodes. Sure, that’s a lot too but not compared to the alternatives.