The basic unit of the cluster is a set of eight networked Pis, called an "OctaPi" — one thing you have to admit is that the Raspberry Pi name lends itself to silly variations. Each OctaPi can be used standalone or hooked up to make a bigger cluster. In the case of the Bramble a total of eight OctaPis makes the cluster 64 processors strong. In addition there are two head control nodes, which couple the cluster to the outside world. Each head node has one Pi, a wired and WiFi connection, realtime clock, a touch screen and a camera.
This is where the story becomes really interesting. Rather than just adopt a standard cluster application like Hadoop, OctaPi's creators decided to develop their own. After three iterations, the software to manage the cluster is now based on Node.js, Bootstrap and Angular.
So what is it all for?
The press release says that:
"The initial aim for the cluster was as a teaching tool for GCHQ’s software engineering community."
and then goes on to say:
"The ultimate aim is to use the OctaPi concept in schools to help teach efficient and effective programming. Watch this space for more details!"
The second point seems a bit unlikely.
Is it going to be open source?
Given that this is a GCHQ creation it seems unlikely, but we can hope.