Energy cost savings were increased from to 54 percent from 27 percent by targeting UPS and cooling systems. Click image for full-sized view.
During tests conducted recently by the CRN Test Center of Dell's C6145 PowerEdge server, which packs two server nodes, 96 processor cores and 1 TB of memory into a single 2U cabinet, we began to think about how such server density might compare with cutbacks in a public transportation system. As more and more people cram into fewer and fewer buses and trains, each vehicle must consume more energy to bring riders from Point A to Point B.
Aside from the obvious issues -- longer lines, fewer seats and other innocuous problems that are borne by hapless riders, increased energy consumption and its associated costs are often overlooked by the central planners, who argue over how best to spend new-found cost savings gained from cutting public transportation by half.
The same thing can happen in the data center in a number of ways, and can occur even if you're paying close attention to the efficiency and power usage of devices that you're deploying. "Typically, data centers were built years ago and were not designed for today's efficiencies," says Philip Fischer, data center business development manager at APC by Schneider Electric. Simply adding modern, efficient equipment to an existing data center can reduce or limit overall efficiency if it's not managed properly.
Fischer described a case study in which one company consolidated and virtualized the servers in its data center by a ratio of about 20 to 1, which alone reduced power consumption cost by about 27 percent (see Figure 1). "It's interesting to note, however, that their PUE went from 2.04 to 2.56," said Fischer, referring to the power usage efficiency figure that results from dividing a facility's total power usage by the energy used by just the IT equipment. Lower PUE numbers indicate higher efficiency.
"Their PUE declined because they had a higher ratio of wasted energy to the actual energy used by the IT equipment," he said. After modernizing some infrastructure equipment and right-sizing some others, the company brought its PUE down to 1.61. Google is considered an industry leader in data center energy efficiency with a PUE of 1.21. "After they went one step further to optimize the power and cooling with close-coupled systems, they were able to increase savings and efficiency much more."
The measurements were performed using APC's TradeOff Tools (tools.apc.com), a set of free calculators that the company offers resellers and end-users for figuring out power usage, UPS requirements, carbon footprint size, and myriad other power-related functions.