Disk drive enhancements for the IBM System Storage DS4000 series midrange disk systems are designed to increase the storage capacity and flexibility of the DS4000 series. The high-speed, higher-capacity, 4 Gbps, 450 GB/15,000 rpm Fiber Channel (FC) Enhanced Disk Drive Module (E-DDM) option increases the physical storage capacity of the DS4700 and DS4000 EXP810 Storage Expansion Unit to 1 terabyte (TB).