A host is a physical machine whose resources would be used by your OpenStack cloud.
All OpenStack resources are virtual and they function atop hosts. In OpenStack, you must configure hosts to perform specific functions.
Platform9 supports the Linux-based operating systems Ubuntu and CentOS with KVM as the hypervisor for OpenStack deployment.
Apart from Linux-based operating systems, Platform9 supports the VMware virtualization platform.
In order to use OpenStack and create OpenStack resources, you must designate one or more hosts as hosts for hypervisor, block storage, image library, and/or DNS functions.
One host can perform multiple functions.