Abstract: An enclosure system for receiving a number of plug in computer peripheral devices, such as hard disk drives in a disk array, utilizes front and rear cages or enclosures that are separated by a vertical backplane having internal circuit interconnections and multi-pin docking connectors on each face. A front bezel provides access to the backplane through the front cage enclosure, so that trays containing the drives can be inserted and plugged into the connectors. The vertical spacing is arranged to be modifiable, so that different numbers of higher profile and lower profile devices can be used. Power supplies, battery back up units and a cooling fan device, all arranged in sub-modules insertable through the rear open face of the power supply enclosure, interconnect with connectors on the back face of the backplane, and cooling air is circulated throughout from front to rear, via apertures in the backplane.