PUE Limbo, what exactly does this title imply? Readers can apply one of two definitions to this title:

1. It's about data center power usage stuck in some in-between phase a' la Canto IV of Dante's Inferno describing the in-between realm known as Limbo. 
2. The traditional and popular dance contest that originated on the Island of Trinidad.

The simple answer is each definition is applicable for PUE Limbo. Every data center manager knows that PUE is a metric that compares a facility's total power usage to the amount of power used by its IT equipment. It's also common knowledge for these same folks that lower PUE can be achieved by implementing industry best practices such as retrofitting older facilities with off-the-shelf equipment for more efficient power distribution.

As our first title definition implies, some data center managers are stuck “in-between,” leveraging the most efficient power distribution devices and those that continue to use more energy than necessary. However, as our second title definition implies, it's a virtual dance to see how low you can actually go. In terms of PUE, a perfect number is 1.0 meaning all the power drawn by the facility is put to use. So unless you are Google and can build servers below $1,500 apiece, with no enclosures so the motherboards go straight into the racks, you need a good plan for achieving a low PUE ratio.

If you’re building a new data center, achieving a lower PUE can be derived by simply picking a better location. For example, Prince Edward Island in Canada offers a much cooler climate over Prince Edward Islands in South Africa. Cooler climates come with less energy consumed to keep servers running at optimal conditions. And isolating hot and cold air to maintain proper airflow, while increasing the ambient temperature by just a few degrees is a no-brainer option. But other methods of achieving a low PUE are a bit more elusive--including optimization at the rack level. After all, server-rack designs have a direct impact on a data center’s PUE.

Think Small for Big Results

The truth is, data center managers don't need to bend over backward to lower their PUE ratios. In many cases, they can reduce power loss by using high-efficiency UPS systems that improve power distribution and eliminate unnecessary voltage conversion.

Another “think small for big results” option is to use intelligent PDUs. Intelligent PDUs are often referred to as Network PDUs or IP power strips. They are usually vertically oriented and distribute power to multiple computing devices via outlets situated in a narrow metal casing.

Today, PDUs have evolved to become a more sophisticated means of power distribution. For example, 3-Phase rack PDUs are now used in a wide variety of power configurations. These intelligent devices contain interesting PUE-lowering characteristics such as providing the ability to:

• Meter the power input and output at the unit including usage, quality, and capacity
• Leverage DCIM software packages to receive and manage alerts as well as monitor and measure PDU devices
• Turn power on and off, both to the individual receptacles and groups of receptacles, at the unit — remotely
• Support environmental monitoring sensors

These intelligent devices truly help control costs and improve operational efficiencies at the power distribution level while allowing for greater capacity planning and better utilization of the overall electrical systems.

No longer should data center managers be stuck in that in-between phase once the electrical infrastructure is installed and energized — because the once inflexible PDU components have now become flexible. For example, inflexible PDUs have only static C20 plugs, if you need to change half the rack with new servers that arrived with C14 plugs — goodbye PDU!

Today's flexible PDUs are UL-tested and a hybrid of the C13 and C19 outlets in a single-phase receptacle. This new version allows data center managers to plug either a C20 or C14 into the same exact spot on the PDU — introducing a great deal of flexibility, while also providing the option to be outfitted with data center environmental sensors. And when intelligent PDUs are introduced, managers now have rack-based environmental monitoring at their fingertips to:

• Consolidate environmental and power system monitoring
• Help improve the operational efficiency of the data center cooling system
• Offer predictive trending of environmental data
• Alert managers of environmental issues on a rack-by-rack basis

So when it comes to looking at a data center’s PUE, don’t be stuck in limbo! Remember the options at the rack level are meant to break out those stagnant, power distribution options while enabling the energy monitoring flexibility that will positively impact the PUE ratio on that “how low can you go?” journey to 1.0.