UCS Central is the manager of managers (=UCSM).
In terms of scale, UCS Central is designed to manage 10,000 servers, corresponding to roughly 70 – 125 UCS Management domains, depending on domain size. UCS Central 1.2(1a) has been tested with 100 UCS Mini domains plus 70 classic UCS domains.
see eg. https://communities.cisco.com/servlet/JiveServlet/download/35264-5-73372/UCS%20Central%20Best%20Practices%20v2.3.1.pdf
