The ZS5-4 controller connects to external storage through a 4-port (4x4) SAS HBA. You can attach from one to forty-eight disk shelves to the controller, including disk shelf configurations with fully populated flash-based SSD data devices. To improve read performance, the ZS5-4 controller does not contain read cache devices, and such devices can be included externally in disk shelves. For disk shelf configuration details, see Disk Shelf Configurations. The ZS5-4 does not support the Sun Disk Shelf.