The ZS7-2 controller connects to external storage through 4-port (4x4) SAS HBAs. You can attach from 1 to 48 disk shelves to the ZS7-2 high-end controller, or 1 to 16 disk shelves to the ZS7-2 mid-range controller, including disk shelf configurations with fully populated flash-based SSD data devices. For ease of cable management, all connections from the ZS7-2 controller to DE3 disk shelves are made using active optical SAS cables (AOC). For disk shelf configuration details, see Disk Shelf Configurations.