Enhanced Linked Mode connects multiple vCenter Server systems together by using one or more Platform Services Controllers.
Enhanced Linked Mode lets you view and search across all linked vCenter Server systems and replicate roles, permissions, licenses, policies, and tags.
When you install vCenter Server or deploy the vCenter Server Appliance with an external Platform Services Controller, you must first install the Platform Services Controller. During installation of the Platform Services Controller, you can select whether to create a new vCenter Single Sign-On domain or join an existing domain. You can select to join an existing vCenter Single Sign-On domain if you have already installed or deployed a Platform Services Controller, and have created a vCenter Single Sign-On domain. When you join an existing vCenter Single Sign-On domain, the data between the existing Platform Services Controller and the new Platform Services Controller is replicated, and the infrastructure data is replicated between the two Platform Services Controllers.
With Enhanced Linked Mode, you can connect not only vCenter Server systems running on Windows but also many vCenter Server Appliances. You can also have an environment where multiple vCenter Server systems and vCenter Server Appliances are linked together.
If you install vCenter Server with an external Platform Services Controller, you first must deploy the Platform Services Controller on one virtual machines or physical server and then deploy vCenter Server on another virtual machines or physical server. While installing vCenter Server, you must select the external Platform Services Controller. Make sure that the Platform Services Controller you select is an external standalone Platform Services Controller. Selecting an existing Platform Services Controller that is a part of an embedded installation is not supported and cannot be reconfigured after the deployment. For information about the recommended topologies, see http://kb.vmware.com/kb/2108548.