Power · Hardware
PDU
Also known as: Power Distribution Unit, Rack PDU, Intelligent PDU
Distributes power from a single feed to multiple devices in a rack. The power strip for server infrastructure — built for the density, reliability, and monitoring requirements of production environments.
A rack PDU takes one input (from a UPS, breaker, or generator transfer switch) and distributes it across many output receptacles — typically C13 and C19 IEC outlets, the standard connectors on server and networking equipment.
PDU tiers
Basic PDU — passive distribution, no intelligence. Power comes in, power goes out. No monitoring. Appropriate only where cost is the dominant concern.
Metered PDU — displays total input current draw on a small display. Lets you see how loaded a circuit is without a clamp meter. Important for avoiding tripped breakers.
Monitored PDU — network-connected, reports per-PDU current, voltage, and power consumption to a management system. Lets you track load trends, receive alerts before a circuit trips, and correlate power consumption with equipment.
Switched (intelligent) PDU — everything in monitored plus per-outlet remote on/off and reboot. Allows you to remotely power cycle a hung device without physically accessing the rack. Per-outlet current monitoring shows exactly what each device draws. The right choice for production server rooms where remote management matters.
Input configuration
Single-phase input — standard for small deployments. A NEMA L5-20 or L5-30 input (120V) or L6-20/L6-30 (208V) is typical.
Three-phase input — for high-density racks. A single three-phase PDU can distribute 10kW or more across balanced phases. A three-phase NEMA L15-30 or L21-30 input connects to the breaker panel or transfer switch.
Dual PDU / A-B redundancy
Production racks typically have two PDUs — PDU A and PDU B — fed from independent circuits or separate UPS units. Each server with dual power supplies connects one PSU to PDU A, the other to PDU B. If any single PDU, circuit, or UPS fails, every device continues running on its remaining power supply.
This A-B redundancy model is the standard for any environment where uptime matters. Don't share both PSUs of a critical server on the same PDU.
Zero-U mounting
PDUs are often mounted vertically in the side channels of a rack rather than occupying rack units. This "zero-U" mounting preserves full rack unit capacity for equipment while keeping power distribution organized and accessible.