At this point in time there is not enough data to completely construct analytical models to determine optimal implementation.
However, the discussions in this paper can serve as a guide for evaluating available alternatives. Initially,an application needs to be studied to develop specifications in terms of computational requirements (processing, memory,I/O) and RTO. Both common as well as relatively rare disasters need to be considered in order to estimate their impact. RPO may depend on the nature of the arriving transactions. Some cloud service providers provide calculators or pricing guides that permit estimation of costs. There exists some literature that provides examples of such computations. Several feasible alternatives should be identified and evaluated.