having 4 computers running software (the same or different software, it doesn't really matter) is known to not give you fault tolerance. See http://sunnyday.mit

having 4 computers running software (the same or different software, it doesn't really matter) is known to not give you fault tolerance. See http://sunnyday.mit.edu/papers/nver-tse.pdf http://sunnyday.mit.edu/papers/nver-tse.pdf