OpenStack Nova also uses real servers as if they were virtualized guest machines. Users can be given real server and virtual machines as guest machines in a transparent manner. This allows you to use real machines for some tasks you already know will be heavy loaded and could have an impact the performance of your cluster.

Until the Icehouse release, it was possible to use baremetal machine by using the Nova-Baremetal backend, but since the Juno release, the current right way is by using OpenStack Ironic.

This option can even be considered for security reasons, since if you use Ironic (or Nova-Baremetal) you'll end up having a single virtual machine on the physical server. This means that this server will not share computing resources (RAM, CPU, and so on) with other virtual machines, preventing any consequence of a possible hypervisor breakout.