Power Distribution Unit (PDU) Basics

Power distribution unit (that's what PDU stands for) or sometimes also called a power strip is a device designed to distribute electric power through multiple outlets. It allows you to remotely turn on, turn off, and reboot gear running on AC and/or DC power. PDU technology is absolutely critical to minimize wasted driving out to remote sites. Instead of sending out a technician and burning time, fuel, and wages on the road, you can issue power control commands remotely via a simple LAN connection.

These pieces of equipment come in several forms but all serve the same basic function.

The term PDU can be linked to two major styles of hardware power devices.

Common uses for the PDU

PDUs are used in server rooms, data centers, remote telecom sites, and anywhere else that gear may need to be toggled on or off (including remote reboot) without someone physically being on-site. PDUs are used in telecom, transportation/transit, public utilities, government, military, education, and research environments worldwide.

Get the Right Power Distribution Unit for Your Site's Power

There are many different kinds of PDUs out there, so you need to make sure that you choose the right one. Your #1 concern is AC vs. DC power. Although internally they may be quite similar, an AC-powered PDU has very different connectors than a DC-powered PDU. If you don't have the right connectors, you're not going to get much use out of your PDU at all.

Some PDU Units Provide Remote Access

Common methods include a RS-232 serial connection or a LAN network-controller accessible through monitored protocols, SNMP, or a web page. This allows an administrator to access the PDU from a remote terminal and interface with it to turn outlets on or off, to schedule power shutdowns, to control load, etc. This can be helpful if a remote machine has gone into an unresponsive state and will not restart through normal means. An administrator can connect to the PDU the machine is plugged into to power-cycle the machine.

One of the challenges in selecting PDUs for a data-center application is to balance the cost of the rack-PDU in the context of an organization's energy-management goals. Inexpensive rack-PDUs may distribute power effectively, but they offer little if any understanding or control of that energy flow.

With energy costs rising over the past several years (circa 2010), IT professionals have begun to take a more comprehensive view of power management with rack-PDUs with more intelligence. The trend is more intelligence and higher-quality rack-PDU devices.

If you want your PDU to be more than an over-hyped surge protector, you need to choose one that has an integrated power management interface. A web interface is the best option for small PDU deployments, because you can access the PDU from any LAN-connected PC on your network. You'll simply type the PDU's IP address into your web browser. From there, you can toggle power on and off.

A web interface is also superior because it travels over reliable LAN transport. Older options include RS-232 serial connections, Telnet, and SSH.

Also, look for a PDU that allows you to switch on, switch off, and remotely reboot gear on a per-port basis. You shouldn't have to toggle the whole power strip all at once.

Your PDU Should Also Include Alarm Monitoring

Simple PDUs are available from many different manufacturers, but there are a few that include more functionality than the rest. As an example, the Remote Power Controller 100 is a PDU and RTU (Remote Telemetry Unit) in one box. The PDU functionality allows you to control power, while the RTU capabilities allow you to monitor discrete and analog alarm data from your important gear.

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