The 3U storage server consists of a dx340 system-board tray, a dx360 M2 system-board tray, or a dx360 M3 system-board tray and up to twelve 3.5-inch hot-swap SAS or SATA hard disk drives installed in a 3U chassis.
This example shows one dx340 system-board tray and twelve 3.5-inch
hot-swap hard disk drives installed in a 3U chassis. 
Note: The system-board
tray drive bay is not used in the 3U storage server configuration.