The cluster is controlled by a Raspberry Pi B+ that I had sitting in my drawer because I blew the serial UART on it working on another project, but the other GPIO's on it still worked so it seemed perfect. I decided to make the Raspberry Pi handle switching power to the nodes and providing a DHCP server. I was going to use it as a TFTP boot server too but in the end I just elected node-1 as a master with some 2.5" disks attached to it because that was already going to serve as NFS storage for the rest of the cluster.

The switch is just a cheap 5 port TP-Link gigabit switch that I picked up at my local computer store. I ripped its case off and designed a simple L shaped front panel that was 3D printed. Sadly I ran out of green filament so I used yellow as the next closest thing, but in the end the whole thing started to look like a bit of a clown costume.

The LED's are hooked up to two 74HC595 shift registers on a daughter board that connects to the Raspberry Pi GPIO header. Next the fun begins of wiring up the 12 LED anodes. I'll post some schematics of the control board and the ATX module soon.