I'm not talking about an IBM mainframe. The definition Google gives me for mainframe is `a large high-speed computer, especially one supporting numerous workstations or peripherals`, which is exactly what my machine is.
* hot-swap power & CPUs
* RAS (Reliability, Availability, Serviceability)
* vendor SLAs
* fault containment
* designed uptime vs achieved uptime
mainframe (noun)
main· frame ˈmān-ˌfrām
1: a large, powerful computer that can handle many tasks concurrently and is usually used commercially
2: (dated): a computer with its cabinet and internal circuits especially when considered separately from any peripherals connected to the computer
The features you list are great to have, but my setup fits the first definition of mainframe as described. If you feel this definition is not specific enough, email Merriam-Webster and don't bother me about it.