Energy Best Practices

A Contrarian Consensus
The greenest data center is the one that you don't build; the greenest server or storage device is the one that you don't buy; and the greenest watt of electricity is the one that you don't use.

Planning the Work, Working the Plan
Fewer than half of organizations monitor the energy consumption of their data centers, according to a 2007 study by the Economist Intelligence Unit. The co-location of data centers in dual-use buildings often makes it difficult to meter IT energy consumption separately. As a first step, uninterrupted power supply systems can act as a surrogate in monitoring power consumption by mission-critical gear. What is a data center operator to do?

Draw on Best Practices

• Assess and plan.
• Consolidate and ladder refreshes with energy-efficient replacement servers.

Get Dense

• If you must own, share.
• If you must operate your own, then consolidate, modularize, virtualize and rethink floor space.
• If you go after your own servers, go after storage too.

Data centers were the original shared service where multiple public entities could avoid duplicate investments in raised floor space, uninterrupted power supply and environmental costs. Looking ahead, systems will consume available power supplies much faster than floor space, and the cost of power is more volatile than real estate.

In one manufacturer's assessment of what it characterizes as a typical data center, 15 percent of power is consumed by storage, 26 percent by computing servers and fully 59 percent is consumed by cooling.

Consolidation and virtualization matters because low server utilization rates waste energy and virtualization increases utilization. Finally modular design lets systems run at load - where energy performance is at its peak - or alternatively, to turn off when not at capacity.

Cool Running, not Cold
Data centers should not be mitten- or sweater-cold, yet data center employees often sport the layered look to be comfortable at work. There is sometimes historic or cultural resistance to the idea of raising temperatures in the data center out of concern for the operating temperatures of mission-critical machines. Yet the American Society of Heating, Refrigerating, and Air-Conditioning Engineers may expand its recommended specifications for server temperature by as much as 80 percent and humidity ranges by 60 percent, suggesting there might be operating tolerances to be exploited.

To those ends:

• Aggregate high-demand systems and use rack- or row-based cooling systems to do what room-based air conditioning cannot.
• Make sure heating, ventilation and air conditioning systems are working for you, not against you. Lukewarm isn't a solution. Separate the hot aisle from the cold aisle.
• Run chillers at off-peak hours and use stored energy during peak loads.
• The installation of blanking panels - pieces of metal that prevent air recirculation - can reduce energy loss through unused vertical space in open-frame racks and rack enclosures, which creates unrestricted hot air recycling and causes equipment to heat up unnecessarily.
• Lawrence Berkeley National Laboratory suggests that data centers can tap cooler seasonal weather to economize by using air-side economizers, which typically sense and filter outside air and allow it to enter the data center when conditions, such as temperature and humidity, are within acceptable engineering parameters.