vSphere 6.0 introduces vCenter Server with an external Platform Services Controller and vCenter Server with an embedded Platform Services Controller.
vCenter Server and the Platform Services Controller are deployed on a single virtual machine or physical host. vCenter Server with an embedded Platform Services Controller is suitable for smaller environments with eight or less product instances.

To provide the common services, such as vCenter Single Sign-On, across multiple products, you can connect multiple vCenter Server instances with embedded Platform Services Controllers. You can do this by replicating the vCenter Single Sign-On data from one of the embedded Platform Services Controllers to the other Platform Services Controllers.
This way, infrastructure data for each product is replicated to all of the Platform Services Controllers and each individual Platform Services Controller contains a copy of the data for all of the Platform Services Controllers.