Query about vCenter Upgrade 5.0 to 5.5

I am doing a project on vCenter upgrade from 5.0 to 5.5 and we have a vcenter in linked mode so as we all know that 5.0 does not have the SSO and Inventory Service enabled and configured so while upgrading how do we deal with this , should i install the both components on the same server where the Vcenter Database is configured or any another place. My vcenter database is configured as a SQL one and its on different machine.(separate server).

Thanks