1. A computer program product for predicting performance of a system comprising a plurality of server tiers, the computer program product comprising: a storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: collecting, for a base allocation of computing resources across multiple server tiers in the plurality of sever tiers, a first set of performance information associated with the multiple server tiers for a set of workloads; generating, on a tier-by-tier basis, a set of experimental allocations of the computing resources, wherein each of the set of experimental allocations varies the computing resources allocated by the base allocation for a single server tier of the multiple server tiers; collecting, for each of the set of experimental allocations, a second set of performance information associated with the single server tier for a plurality of workloads; and predicting at least one performance characteristic of one or more candidate allocations of computing resources across the multiple server tiers for a given workload based on the first set of performance information and the second set of performance information.