[stuxnet79]

The one factor that distinguishes a typical HPC installation from what we would typically call a 'cloud' system is the throughpout. HPC installations are designed to provide maximum throughput and this requires very specialized hardware and networking infrastructure (InfiniBand). Cloud installations in contrast make use of widely available commodity hardware (e.g. Raspberry Pis). Unless the tasks you want to do will require an enormous amount of throughput for inter-node messaging within your cluster, then I'd suggest orienting your plans towards the 'cloud' model aka using commodity hardware and taking advantage of an open source cloud platform like OpenStack.