Brandon Van Ryswyk and Daniel Chin have just finished building a 32-node DataStax Enterprise cluster running on Raspberry Pis. It’s being used to demonstrate the fault-tolerant nature of Cassandra by letting visitors to their lobby take down a ‘data centre’ with a touch of a big red button. Cassandra is a database platform used in a lot of ‘big data’ applications. You can read a lot more detail about the project on their website.