OpenNebula is a simple yet powerful turnkey solution to build clouds and manage data center virtualization. It includes all the features needed to provide an on-premises (private) cloud offering, as well as public cloud services, and it has a sandbox on Azure.
"What we can say up to now: We use OpenNebula; that's it. No big issues, no big efforts in performance-tuning. The infrastructure runs and runs and runs," said Armin Deliomini, IT Systems Engineer at Runtastic.