Choosing A Power Distribution Unit (PDU) For Your Server Closet Or Server Room

Whether you like to call your physical server location a "server closet" or a "server room", it's important to choose the right power distribution unit (PDU), and here's why:

In server environments, a power distribution unit is typically used for remote reboot applications. The next time one of your servers freezes, locks up, hangs or otherwise fails, you'll be able to correct the problem without having to manually power cycle that server.

The ability to remotely reboot servers and other gear valuable at any company. It's especially important when you have a long distance between your workspace and your server room/closet.

Look for Rack-Mount Power Distribution Units.
Power distribution units come in many shapes and sizes, but the best ones for server room applications are rack-mountable. This is simply because your PDUs belong on your server rack - right next to servers that they'll be controlling.

This PDU is AC-powered
An AC Power Distribution Unit example - This is the front-panel of an AC Remote Power Controller 100.

While some people might be concerned with the physical space consumed by a rack-mounted PDU, you can minimize the rack space by choosing a one RU power distribution unit. You can most likely get plenty of power outputs (about 8) on the back of a single-rack-unit PDU.

Before You Choose a PDU - Take a Look at your Redundant Server Power Inputs.
One of the defining characteristics that separates great PDUs from the rest is the ability to handle servers with redundant power supplies. Just because your server has two or three redundant power inputs you shouldn't have to struggle to reboot it. Think about it.

Issuing a remote reboot command is simple if your server only has one power supply. You press one button in the PDU's web interface or other interface, and a power relay turns off. It then waits about a second and turns back on to reboot your server.

Now think about the same scenario with a redundantly powered server instead. Killing power to just one power input won't cause a reboot - you have to hit all of them at once. With an automated power cycle time of just 1 second, timing is going to be tricky.

What you'll likely end up doing, of course, is issuing a manual "power off" command to each server power supply. Then wait a moment, and empowering each server power supply back on. But there has to be a better way, and (fortunately) there is.

If you have servers with redundant power supplies, you really need to find a power distribution unit that understands this fact. You should be able to configure your PDU to "link" several power outputs together in its software. This will allow you to issue a single remote reboot command for your servers - no matter how many power supplies they may have.

Understand the value of a convenient web interface for accessing your power distribution units.
The better PDUs out there on the market include convenient web interfaces for issuing power commands. You'll be able to log into this web interface from any PC on your network with nothing but a web browser. If you've ever accessed the web interface on a home network router, you know exactly what we're talking about here.

Even more important than ease-of-use, a web interface means there's no software to install. This is a big plus in organizations where every software installation involves getting special permission from the IT department.

Don't skimp when you're looking at PDUs for your valuable servers.
Everyone likes to save money, and that's a fantastic instinct to have. What you need to watch out for, though, is a $1 savings today that ends up costing you $10 in the future.

How much money do you have invested in your server room or server closet already? Take a minute to get a rough total in your head. It's likely a big number.

Your existing investment in your servers is big, so you need to protect it with a high-quality power distribution unit.

When you're shopping for PDUs, look for a sturdy, powder-coated metal chassis. Also, look for power outputs that have a high enough amperage rating to meet your needs (10 amps is usually a good number for each output).

Another ingredient for a quality power distribution unit is a manufacturer who has been in business for at least 10 to 20 years. This ensures that you're buying not only from someone whose business is stable, but also someone whose products have been successfully deployed in networks around the world. Don't trust your valuable servers to a power distribution unit vendor that doesn't have a proven technology.

Who doesn't like a bonus? Get alarm monitoring included with your PDU.
You can get a simple, no-frills PDU from many different manufacturers, but choosing the right vendor can get you a lot more functionality in the same box.

Consider the case of the Remote Power Controller 100, a power distribution unit that also includes network alarm monitoring. This is an excellent way to get double duty out of your investment in a PDU. Not only will you be able to control power and reboot your servers remotely, you'll also be able to monitor their status with discrete inputs (contact closures) and analog inputs.

Now, keep in mind that the Remote Power Controller 100 is also available without alarm monitoring functionality if you decide that you really don't need it. Still, most people find after looking at their server room or server closet environment that they can benefit from adding alarm monitoring at such a small incremental cost to their PDUs.