Data storage apparatus comprising a main housing containing an electric power supply, a panel supporting a plurality of electric connectors for connecting the power supply to other component parts of the apparatus and a plurality of units. Each of the units comprises a plurality of data storage elements and is mounted to slide from within the main housing to provide access to its data storage elements.The apparatus also comprises a plurality of cable modules each comprising a cable having a first connector at a first end connected to one of the units and a second connector at a second end connected to an electric connector on the panel. The cable modules also include a moveable rigid structure providing a barrier preventing manual access to the panel. The second connector is attached to the rigid structure such that movement of the rigid structure causes the second connector to be disconnected.