In a server infrastructure, the power supply is often the forgotten link. However, a poor choice of PDU (Power Distribution Unit) can jeopardize an entire rack cabinet. This guide explains everything you need to know to choose the right PDU.
What is a PDU?
A PDU, or Power Distribution Unit, is a rack-mounted device that distributes electrical power to multiple servers, switches, and equipment from a single source. Unlike a standard power strip, a PDU is designed to:
- Fit into a standard 19" rack (0U vertical or 1U horizontal format)
- Support high loads (16A, 32A, or more)
- Handle industrial connectors (IEC C13, C19, IEC60309)
- Ensure the electrical safety of the entire rack
The 4 types of PDU
1. Basic PDU (Passive)
The simplest type: it distributes power without any monitoring functions. Ideal for small setups or tight budgets. Reliable and requires no configuration.
2. Metered PDU
Includes a display or interface to measure total power consumption. Allows monitoring of overall load without switching or controlling individual outlets.
3. Switched PDU
Allows turning each outlet on or off individually, remotely via the network. Perfect for remotely rebooting equipment without physical access to the server room.
4. Smart PDU (Intelligent)
The most advanced level: per-outlet measurement, alerts, SNMP, web interface, DCIM integration. This is the category of the Raritan PX3-1292R, a smart 32A / 7.4 kVA PDU with 12 C13 outlets and IEC60309 input, perfect for high-density racks.
Choosing your PDU: essential criteria
Amperage and power
Calculate the total consumption of all your rack equipment (servers, switches, NAS, etc.). Add a safety margin of 20 to 30%. For a rack filled with HP ProLiant Gen8 / Gen9 servers, a minimum 32A PDU is generally recommended.
Number and type of outlets
1U / 2U servers almost all use C13 connectors (for PSUs up to 10A) or C19 (high-power PSUs). A PDU with 12 to 24 C13 outlets covers most standard configurations.
Rack format: 0U vs 1U
- 0U vertical: mounts on the side of the rack, does not consume rack units.
- 1U horizontal: installs like a standard device, easier to access.
Single-phase vs Three-phase
For a small server room or a single rack, single-phase is sufficient (230V / 16A or 32A). Three-phase is reserved for data centers and multi-rack installations.
PDU and HP ProLiant servers: best practices
HP ProLiant servers (generations G1 to G10) generally have redundant Hot-Plug power supplies. To fully benefit from this, connect the two PSUs of each server to two different PDUs, each powered by separate electrical circuits. This ensures total electrical fault tolerance and maximum uptime.
Used PDUs: a reliable economical alternative
Professional PDUs (Raritan, APC, Eaton) are robust devices designed to last 10 to 15 years. Buying a refurbished or used PDU can cut costs by 2 to 3 times without compromising reliability if the equipment has been tested and inspected. At IT & Office, all our PDUs are tested for functionality before shipping.
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