An approach is provided for determining availabilities of servers in multiple tiers of a workload. Based on (1) a required availability of the workload, (2) resource requirements for redundancy groups (RGs) in the workload, (3) sets of server sizes, and (4) sets of availability categories, numbers of server(s) included in respective RGs are determined, allocations to the server(s) of one or more server sizes from a selected set of server sizes are determined, and allocations to the server(s) of one or more categories of availability from a selected set of categories is determined, so that a cost of achieving the required availability of the workload is minimized.