PDUs can be mounted inside your server rack wherever you need a source of power for your equipment. You can mount them vertically along the side rails or in the back of the enclosure, or horizontally within the rack, in the same space as a server. Each rack must safely deliver stable electrical power to dozens of servers, switches, and storage devices while maintaining reliability, airflow efficiency, and electrical safety. Modern infrastructures. Power distribution units come in two form factors: floor standing or cabinet PDU s and rackmount PDU s.