The Raspberry Pi is an amazing, cheap single board computer designed to hook up to a TV and help with teaching programming.
I was inspired by a story from Southampton University in the UK to build my own (but rather more modestly sized) Raspberry Pi cluster. The cluster has 4 worker nodes (Rev 2 model Bs with 512Mb RAM), and 1 head node (Rev 1 model B with 256Mb RAM). Each of the nodes run Raspbian.
The cluster also contains a 5-port ethernet hub, an excellent (raspberry-shaped) pihub to power the 4 worker nodes, and another small USB hub to power both the head node and a Wi-Pi wi-fi dongle that lets the cluster communicate with my wi-fi router and the wider interent.
The following system diagram should hopefully make it clearer how the nodes in the system are connected.
I know lego is more trendy but I happened to have some meccano handy (preserved from my childhood). Each of the components is bolted onto a pre-cut 3mm X 68mm x 110mm red fluorescent acrylic sheet supplied by sheetplastics.co.uk (The dimensions were chosen to be in proportion to the Golden ratio). The sheets are then bolted onto meccano supporting struts, in four stacks arranged in a cross formation.
The obligatory shot of the cluster running in the dark, with twinkly lights:
What worked: I was able to cut up an old ethernet cable into sections that are just long enough to connect each node to the router.
What didn't work: I tried to make my own short micro USB cables and PSU arrangements but soldering onto tiny micro USB plugs was very awkward. I wasted a lot of time before I simply ordered the pihub and (from e-bay) 4 short 30mm USB charger cables.
Next steps - in part 2 I describe more about how the networking for the cluster is configured.