Hardware Today: Keeping the Server Room Juiced Page 2
Getting in Condition
Getting the power to the servers is one problem. Another is making sure it is noise-free and at the right voltage. While UPSes and surge suppressors take care of the large spikes that can damage the equipment, one must also address the small voltage fluctuations. According to a study by Bell Labs, blackouts and surges higher than 200 volts caused only 3.8 percent of power-related issues, while voltage sags and voltage surges less than 200 volts accounted for 96.2 percent of the problems.
But power is not a stand-alone characteristic more power means more heat. Concentrating power usage concentrates the heat and raises problems getting the airflow where it is needed. The resulting extra cooling costs may then exceed any savings from using less space.
Surge protectors do a good job against lightning strikes and UPSes prevent blackout losses, but neither is designed to guard against these smaller, more common fluctuations. Isolation transformers filter out the smaller variations, but they are large and expensive. SmartPower has a newer alternative called transformer-based filtering (TBF), which uses transistors, thyristors, capacitors, and relays, together with a small transformer, to condition the power. The devices weigh 17 ounces and cost about $100, making them affordable for even the smallest server closets. Although SmartPower sells UPSes, surge protectors, and isolation transformers, according to Mechanic, "servers, workstations and networking gear can best be protected by using transformer-based filters."
New power products make it easier to support the growing popularity of rack-dense servers. But power is not a stand-alone characteristic more power means more heat. Concentrating power usage concentrates the heat and raises problems getting the airflow where it is needed. The resulting extra cooling costs may then exceed any savings from using less space. So being overzealous is counterproductive.
"We recommend that clients keep their power standards in area of 50 W/ft to 100 W/ft and strive to have an average of 4 kW per rack, including 60 percent for cooling," says Gartner Research Vice President Mike Bell. "When they get over 100 W per foot they start getting into a dysfunctional situation where the heat output is so intense that they see their power costs go vertical."