I've actually seen entire companies and universities run on two physical machines, for sufficiently large values of two physical machines.
When I was working there, the University of Oregon ran almost all of the routine computation and webpages on one big Sun box that was about as fast as my calculator, and one enormous Vax box that was about 8086 level speed.
When I was working there, the University of Oregon ran almost all of the routine computation and webpages on one big Sun box that was about as fast as my calculator, and one enormous Vax box that was about 8086 level speed.