Re: Fiendishly expensive
I've read Cormac's guide, and we have had extensive discussions on this. Any scale-out storage system has the same limitation. Even a traditional storage system with 2 controllers has the same problem... when you do maintenance on 1 controller than you are at risk. The statement here was that the minimum is 4, this is not the case. The minimum today is 2 with an external witness, or 3 full hosts. Yes if you do maintenance you will be at risk, if you want to mitigate that and can afford the associated cost I would always recommend to go with 4. I think I have been pretty clear about that on my blog in the past.
Same applies to HA / DRS by the way, more hosts is better.
PS: I seriously have no customer who has 4 nodes or more and does a full "data evac" during maintenance mode...