Over the weekend I sat down and built a small Raspberry Pi cluster consisting of 4 nodes. I used three Raspberry Pi 2 boards for compute nodes and an original Model B for the head node. I wanted the cluster — more commonly known as a ‘bramble’ — to be as compact as possible, with just two cables coming out, one for power and the other for network. I made use of a USB hub to power the boards, and a small Ethernet switch which I could hack to be also be powered from the USB hub rather from a separate wall wart.