1. A computer-implemented method for selecting a target design for a tier of an architecture of components based on a set of established criteria, comprising: evaluating, by a computer, a plurality of designs satisfying a first criterion based on a number of spare components for satisfying a downtime criterion for the tier and anticipated performance of the components in the tier, wherein each of the spare components is a redundant component that is useable for failover from another component, and wherein the downtime criterion relates to an allowed downtime over a predefined time period; selecting, by the computer, a lowest cost design from the plurality of designs; and establishing, by the computer, the lowest cost design as the target design.