  In the last ten years host virtualization has brought a revolution in the way
almost every activity related to information technology is thought of and
performed. The use of virtualization for HPC and HTC computing, while eagerly
desired, has probably been one of the last steps of this revolution, the
performance loss due to the hardware abstraction layer being the cause that
slowed down a process that has been much faster in other fields. Nowadays the
widespread diffusion of virtualization and of new virtualization techniques
seem to have helped breaking this last barrier and virtual host computing
infrastructures for HPC and HTC are found in many data centers. In this
document the approach adopted at the INFN "Laboratori Nazionali del Gran Sasso"
for providing computational resources via a virtual host based computing
facility is described. Particular evidence is given to the storage layout, to
the middleware architecture and to resource allocation strategies, as these are
issues for which a personalized solution was adopted. Other aspects may be
covered in the future within other documents.
