Computers support hotswapping so that a user can replace a harddrive while the system is running. Is that mostly software just powering off the harddrive or is it some special hardware involved? If there were not special hardware then I suppose that you could hotswap any drive but it seems that the drive must support it in hardware.
Electronic – How do hotswapping computer parts work
It requires several features, some of which put the cost up.
These include additional transient suppression on signals, which may put additional capacitance on bus signals thus requiring additional engineering/testing and may reduce performance below what's otherwise possible.
Also, connectors which longer and shorter pins that ensure that some pins mate before others and disconnect after others. This is to guarantee that signals are connected and disconnected while power and ground are already connected. In some cases, a control pin can be made to connect last and disconnect first, and this pin will tri-state all other signal pins.