Setting up an OpenMPI cluster within a LAN

We have purchased several DELL PowerEdge R640 servers several months ago as computation nodes. What we want to have is to build a small computational cluster so that they can run users’ programmes in parallel. Users prefer to work on Linux and most of the programmes will be written in C / C++ / Fortran. Therefore we are going to build a Beowulf cluster with a head node, or server node, and several computation nodes.