Being able to withstand a data center going down is not just an edge case, it is an absolute necessity for the highly available applications Cassandra powers. While the cloud is far more flexible for production use, nothing beats a big shiny hardware display for a demo.
Our main goal for this project was to take the abstract concept of fault tolerance and make it something you can see in action and interact with.
By pressing a big red button an Arduino cuts the power to a network switch which causes some of the Raspberry Pi nodes to drop out of the cluster. A monitor on the wall displays the health of the cluster and lets you watch as Cassandra recovers from the failed nodes in real time. Great idea to use the Raspberry Pi to demonstrate fault tolerance!