1. A method for communication between a host and a plurality of tape drives of different types via a single physical control unit (CU), said method comprising: providing a plurality of model types L of tape drives, each said model type being of a different generation, and a number of tape drives Q L for each model type; issuing feature codes for a plurality N of logical control units (LCUs) for a customer for the single physical CU; entering the feature codes into the physical CU to enable configuration of N LCUs; configuring the physical CU to 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 Q L , mapping the model types to the N LCUs with priority given in the mapping to the newer generation model types and the model types where Q L is greater than M; and assigning individual tape drives to the LCUs based on model type.