SURFsara (previously SARA) operates a High Performance Computing Cloud as a service for Dutch academic use since October 2011. The cloud is offered as IAAS, so the users of the OpenNebula web-interface are academics who control their own virtual clusters, without being IT professionals. We operate a hybrid cloud with 29 nodes totaling 688 cores and 400TB storage. The High Performance and Big Data requirements caused non-obvious design choices and unexpected system behavior. We would like to share our challenges, solutions and user experiences with OpenNebula 3.x and look ahead to the possibilities in OpenNebula 4.0.