With this optional feature, the IBM TotalStorage DS4300 Midrange Disk System with turbo option is capable of supporting concurrent attachment of DS4000 EXP700 and DS4000 EXP100 Storage Expansion Units. Specialized applications may benefit from a mixed drive system, for example, high-access data on Fiber Channel and near-line or low IOPS data on SATA. Sites with budget restrictions may require a mixed system to save the cost of a second controller module. SATA could be used for internal high-speed backups via Volume Copy or backup software.