SATA/SAS backplane for mounting of up to four 3.5" hard drives, that for instance are combined into a RAID array. The use of a backplane allows an easy replacement of hard drives - also during operation if a hotswap-supporting controller is used. The drives are mounted directly into the trayless chassis and locked in place.
Furthermore there's a saving of space as up to three hard disks are put in an area of two 5.25" hard disk bays. Each tray can be locked individually.
The disks are cooled by an integrated 70mm fan that can operate at two different speeds.