  We present our ongoing work building a Raspberry Pi cluster consisting of 300
nodes. The unique characteristics of this single board computer pose several
challenges, but also offer a number of interesting opportunities. On the one
hand, a single Raspberry Pi can be purchased cheaply and has a low power
consumption, which makes it possible to create an affordable and
energy-efficient cluster. On the other hand, it lacks in computing power, which
makes it difficult to run computationally intensive software on it.
Nevertheless, by combining a large number of Raspberries into a cluster, this
drawback can be (partially) offset. Here we report on the first important steps
of creating our cluster: how to set up and configure the hardware and the
system software, and how to monitor and maintain the system. We also discuss
potential use cases for our cluster, the two most important being an
inexpensive and green test bed for cloud computing research and a robust and
mobile data center for operating in adverse environments.
