When you add an ESX/ESXi host to a vSphere cluster that vCloud Director uses, you must prepare the host before a provider vDC can use its resources. You can unprepare a host to make it unavailable for use in the vCloud Director environment.
For information about moving virtual machines from one host to another, see Move Virtual Machines from one ESX/ESXi Host to Another.
You cannot prepare a host that is in lockdown mode. After you prepare a host, you can enable lockdown mode.