Rack configurations provide increased storage device density without compromising cooling or immediate device availability. A device rack has a frame including posts which define an interior containing system board(s) with electronic device connectors. The system board is fixed relative to the frame, and the rack is devoid of sliding rails and cable management arms for the devices, thereby reducing rack weight and mechanical complexity. A vertical plenum within the rack between loaded system boards carries cooling air for the devices and may also permit use of a service robot to install or replace hot-pluggable hard disk drives or other devices, which can be arranged in columns. As one objective measure of the increased density provided, a connector density is at least a specified number of hundreds of mechanically and electronically releasably connectable electronic device connectors per cubic meter within the rack.