Raspberry Pi is already very famous in the market of the Single Board Computers. Raspberry PI is already acceptable computer in the Do It Yourself (DIY) community. People are using it for IoT products, embedded system products and so on. It also has capability to work as server and running full grade linux. But using multiple Raspberry PI boards many people tried to develop Parallel computing models for different purposes like Machine Learning, Crypt-currency mining or even to run complex numerical analysis like the Supercomputer does.
Recently Oracle developed a Model supercomputer which has 1060 numbers of Raspberry PI connected with it. In recent OpenWorld event Oracle has presented that. This runs proprietary Linux from Oracle itself. They have connected the RPi Boards to a series of switches which is from Ubiquiti UniFi Switch 48s. And the power supply comes from USB based series of power supply to bring up the whole unit.
Oracle engineers mentions that often the Raspberry PI cluster setup are not for performance enhancement but this leads lot of different algorithm to try on a 35$ computer. This may not a professional grade or commercial product but this can give clear image what we can do in terms of innovation with having 35$ computer in hand.