The Lab posted The Hardware Issues Behind Recent Region Restarts yesterday.
This is an excellent description of the problem. If you are unfamiliar with how rack servers are setup you may want a little more explanation.
The image above shows a classy looking rack server. If you have ever used a docking station with a laptop, you have an idea of the way they can work. Not all servers are so easy installed or removed from the ‘rack’.
The image above show a smaller more common rack of servers. The wiring is more typical of what I see in small businesses.
In your computer you have all your connections; power, network (may be wireless), sound, video, keyboard, mouse.
In a rack server there is no need for a monitor/screen. There is no need for a keyboard and mouse as operators connect to the computer via a remote desktop that uses the network. The power supply is also redundant. Rack servers tend toward the highly efficient on the power consumption side. A single medium size power supply can serve numerous rack servers, saving lots of space.
In general rack servers only need a couple of connections. It is easy to build the connectors into a ‘backplane’ for the rack. This is sort of a socket and plug type setup like a docking station. I doubt this is the type of backplane they are referring to.
When one has thousands of computers it is common to move toward micro or blade servers. These are very efficient space saving servers. With rack servers more than one server is often built into the box that goes into the rack. This later type configuration is probably more like what the Lab is using. I suspect their ‘backplane’ is more the component-set shared by four computers built into a single rack unit.