The quad-core i7 model Mac mini was previously available in a server variant with redundant disk drives and either the Server version of OS X (up until OS X 10.7) or a copy of the macOS Server application in versions 10.8 and newer. macOS Server can be purchased from the App Store.
However, Apple removed the server model from the product offering with the Mac mini update in late 2014. We still offer subscriptions of the quad-core i7 Mac mini with redundant hard drives or with a SSD. For CPU-intensive tasks, the i7 Mac mini is the best value. You are free to colocate any model of Mac mini at MacStadium. See related articles for more details about colocation.