1. A tape storage system comprising: a single physical control unit (CU); a plurality of model types L of tape drives, each said model type being a different generation, and a number of tape drives QL for each model type; a host communicating with the plurality of model types L of tape drives via the single physical control unit; the single physical CU configured to: in response to obtaining feature codes for a plurality N of logical control units (LCUs) for a customer for the single physical CU, support N LCUs, each LCU supporting communication with a single model type and a maximum of M tape drives; based on the number of model types L and the number of tape drives for each model type QL, map the model types to the N LCUs with priority given in the mapping to the newer generation model types and the model types where QL is greater than M; and assign individual tape drives to the LCUs based on model type.