It would be a bit odd to build capacity for spot instances. The whole point of low priority, preemptable instances is to fill up the capacity that you have avai

It would be a bit odd to build capacity for spot instances. The whole point of low priority, preemptable instances is to fill up the capacity that you have available, but have earmarked for scheduling big jobs or handling failures (say a power domain or decent chunk of the network goes down). Otherwise they would be no different from any other instance type.