Best Practices for Saving Energy In Data Centers – Facilities Management Data Centers Feature
Data centers’ enormous energy consumption — 2 percent of U.S. electricity use — has gained national attention the last few years. Through the U.S. Environmental Protection Agency’s Energy Star Buildings program, more than 60 large enterprise data centers, run by the most prominent companies in the world, have been certified as energy efficient. In contrast, mid-tier and small data centers (under 20,000 square feet of white space) often do not prioritize energy efficiency, but devote their limited resources to data center uptime and security. Numbering in the millions and located in almost every commercial building, these smaller facilities actually account for most of the data center power draw in the U.S. To help close the energy-efficiency knowledge gap in smaller data centers, Energy Star has identified 12 common data center efficiency opportunities. Often implemented at Energy Star-certified data centers, these best practices include:
1. Hot aisle/cold aisle: Server racks should be oriented so that the fronts of the servers (where the cool air is drawn into the server) always face each other. This orientation creates alternating “hot aisle/cold aisle” rows of server racks, thus separating the cool air from the hot air and allowing air conditioning units to work more efficiently.
2. Containment: Various physical barriers should be installed to further eliminate hot and cold air mixing. Even with a hot aisle/cold aisle configuration, hot and cold air can still mix. Mixing can be minimized by using flexible strip curtains, similar to plastic supermarket refrigeration covers. Two Energy Star-certified data centers — BNY Mellon and RagingWire — employed hot aisle containment during their efficiency upgrades that led to higher chilled water temperatures and energy savings.
3. Variable speed fan drives (VSDs): Computer room air conditioners (CRACs) with VSDs can vary their fan speed with the data center server load. Because fan power varies roughly with the cube of fan speed, one half the fan speed will lead to one-eighth the fan power draw. Four Energy Star-certified data centers — BNY Mellon, Kaiser Permanente, RagingWire, and Target — employed VSDs to save hundreds of thousands of dollars annually, with paybacks ranging from 0.54 to 1.7 years.
4. Other airflow management devices are also worth considering: Blanking panels are thin plastic panels installed in unused rack space so that hot air does not flow directly from the hot aisle to the cold aisle. Staff at Kaiser Permanente used boat covers, underfloor baffles, and blanking panels to eliminate nearly 70,000 cubic feet per minute of bypass air.
Structured cabling systems can eliminate disorderly cables that might constrain exhaust airflow from rack-mounted equipment.
Floor grommets improve cooling efficiency by sealing open areas where cables enter and exit plenums (such as a raised floor). QTS’ enormous 990,000-square-foot Atlanta Metro data center installed vented tiles and grommets and sealed gaps around its raised floor to save over $30,000 per month.
Here are eight more best practices from Energy Star that provide energy efficiency opportunities for smaller data centers. They include temperature and humidity adjustments, air- and water-side economizers, and the elimination of unused servers.
5. Server inlet temperatures and humidity adjustment: ASHRAE has expanded the recommended server inlet temperature to range from 65 to 80 degrees F and expanded recommended humidity ranges to include 42 to 59 degrees F dew point. Many data centers continue to set their thermostats at temperatures that are too low or their allowable humidity ranges too tight. BNY Mellon raised the temperature of its supply air from 72 to 78 degrees F, which allowed it to increase its chilled water temperature from 44 to 47 degrees F, thus lowering cooling costs.
6. Air-side economizer: Because data centers must be cooled 24 hours a day, 365 days per year, cooler evening or winter air can be used to cool a data center even in warmer climates through an air-side economizer. NetApp’s global dynamic laboratory, the first data center to earn the Energy Star certification, owes much of its savings to air-side economizers. Using outside air allows that data center to operate without a chilled water plant for more than 75 percent of the year.
7. Water-side economizer: For data centers with chilled water plants, a water-side economizer uses the evaporative cooling capacity of a cooling tower (instead of the chiller) to cool the data center. This measure is best suited for a large expansion or new construction, as water-side economizer retrofits may have long paybacks.
8. Comatose server retirement: Surveys indicate that 8 to 10 percent of servers are actually not doing anything. Sun Microsystems cut 8 to 10 percent of IT equipment load and 11 to 14 percent of total load by retiring or decommissioning unused servers.
9. Server consolidation: Data center managers can reduce the total number of servers by putting more applications on fewer machines. For example, two or three lightly used file servers can be consolidated onto one machine.
10. Server virtualization: A type of server consolidation, server virtualization allows multiple virtual servers to work simultaneously on one physical host server. Server virtualization has revolutionized data center management — improving scalability, reducing downtime, and enabling faster deployments — and is commonplace in large data centers but much less common in smaller data centers. Southwestern Illinois College performed a detailed three-year total cost of ownership analysis of placing 35 virtual servers on four physical host servers; it showed $280,000 in total savings in direct and indirect costs.
11. Data storage best practices: Automated storage provisioning (right-sizing, re-allocating unused storage, and improving use of existing storage), data compression, deduplication (removing duplicate copies), and tiered storage lead to less storage use and hence, less energy consumption.
12. More efficient IT equipment: Energy Star-certified servers, storage equipment, and uninterruptible power supplies (UPS) consume power more efficiently. Tests conducted jointly by EPA, Hewlett-Packard, and Microsoft demonstrated that a new Energy Star server at low loads consumed 54 percent less power than older, non-certified server models.
These 12 energy-efficiency measures are not cutting-edge technologies that only giant tech companies with high margins can afford. (For example, Google cools one of its data centers with seawater, and Facebook uses direct, not alternating, current to power its custom-built servers.) Rather, these solutions provide a facility manager at a commercial building a viable starting point to begin examining data center efficiency and implementing cost-effective strategies to cut energy savings and associated costs.