It's all the way the cookie crumbles. (Score 0)

Fault-tolerent servers are the way to go for critical applications. Obviously critical applications need quite a bit of computational power too, so I'd consider the best approach to a situation like this would to go with a small cluster of servers, each being redundant. For example, say we have 6 servers to get this operation up and running, what in my opinion will be most reliable would be to do what was mentioned either and do both. It covers all bases, and really makes for a stable networking enviroment. There is an application built into OpenBSD used for making two servers act much like one, I believe it was called CARP. In principle, it can be used to make two servers allocate the primary functions, while the other is on constant standby to take over operations in case of an incident. It might seem like a waste of CPU cycles, but it works out very well, esspecially if you turn 3 pairs of them into one Beowulf cluster.