First of all, I'm not arguing against mainframes or anything! I'm just trying to clarify/explain terms and remove confusion. Just to get that out of the way. >

First of all, I'm not arguing against mainframes or anything! I'm just trying to clarify/explain terms and remove confusion. Just to get that out of the way. > One, quite commonly known, is that two separate mainframes can run completely in lock-step if they are less than ≈ 50 km / 30 mi apart Since they are 50km apart, they are connected to each other by one or multiple cables. I assume that they are also both connected to the internet (or something else that matters) so that if one burns down the other can take over. Correct so far? If so, then please answer this questions: how does the system behave if all the cables between the two machines are severed, for an unknown time?