Traditional database systems have long been plagued by performance problems when there is either an increase in the mainframe usage or in the database applications. Solutions to these problems have been sought, first, by offloading the database system from the mainframe computer to a single, dedicated backend computer. The backend computer has its own disk storage, is used to perform all of the database operations, and interacts with the mainframe. However. database systems with this software single-backend approach still encounter the performance problems when either the backend usage or database applications increase. The software multiple-backend approach to database management and hardware upgrade is therefore proposed to overcome the performance-gains and capacity-growth problems of either traditional mainframe-based database systems or conventional software single-backend database systems. In this paper we specify the design requirements and issues of the software multi-backend database systems. We show how these requirements and issues affect the design and implementation of a multi-backend database system known as MBDS. Since MBDS is designed specifically for performance gains, capacity growth, and hardware upgrade, we benchmark MBDS in order to verify whether its design and implementation can indeed relate the gains and growth directly to the multiplicity of backends in terms of the response-time reduction and invariance.