A host group is a vSphere host DRS group. A vSphere administrator must create host DRS groups in a resource pool mapped to a vCloud Director Provider VDC before they can be used in vCloud Director VM-Host affinity rules.
vSphere host DRS groups created in resource pools that are mapped to a Provider VDC appear in those resource pools and can be named in VM-Host affinity rules. For more information about host DRS groups, see the VMware vSphere ESXi and vCenter Server Documentation.
Host DRS groups in the resource pool are listed on its Host Groups tab.