|Автор: Rich Miller|
Earlier this month the NetApp Data Center in Research Triangle Park (RTP) in North Carolina became the first facility to earn the Energy Star for Data Centers rating from the U.S. Environmental Protection Agency. The NetApp facility achieved a near perfect mark by scoring a 99 on the 100-point scale used by the Energy Star program.
The RTP facility allowed NetApp to expand its data center capacity to meet its needs through 2019. The 132,000-square-foot building houses a 36,000-square-foot dynamic data center with a designed power load of nearly 25 megawatts. The facility can house 277 terabytes of storage, or enough to hold 28,000 copies of the entire contents of the Library of Congress, or about 15.8 million HD movies.
The NetApp data center is distinctive in its focus on airflow management, with a design that completely separates hot and cold air and provides granular control over air pressure throughout the facility. “We were able to start from the inside out and build around the air handlers,” said Joe Miller, NetApp’s Manager of Facilities Operation at the Research Triangle data center, who provided an overview of the facility at the Silicon Valley Leadership Group’s Data Center Energy Efficiency Summit last fall.
The following pages provide a closer look at the infrastructure of the NetApp facility, and the design that helped it earn the exceptional rating from the Energy Star for Data Centers program.
This diagram shows the airflow design of the NetApp data center, which is optimized to control airflow and pressure to achieve maximum efficiency in the cooling system, which can use fresh air (free cooling), chillers, or a combination of the two
The NetApp RTP data center is a two-story building that employs a top-down cooling system that uses fresh air from outside of the building to cool the server rooms, a process also known as air-side economization or simply “free cooling.” Fresh air is used to cool the data center whenever the outside air is cooler than the return air, which is 97 percent of the year under the operating parameters used by NetApp, which uses only outside air for 67 percent of the year, and a combination of free cooling and chillers for 30 percent of the year. The chilled water plant is the sole provider of cooling only 3 percent of the year.
“A big key is the ability to turn off the chillers,” said Miller. “That’s where we get a huge savings on electricity.”
The air flow management begins on the roof of the building, where air inlets (pictured below) bring outside air into the building.
A look at the air inlet units at the NetApp data center in Research Trianlge Park
Following The Airflow
The second floor of the NetApp data center manages the mix and flow of air through the building. Fresh outside air enters the floor from the rooftop air inlets. When the temperature is cool enough, the air handler units (pictured above) will move the air into the first floor data halls. The air handlers are each located directly above a data hall so the cool air can be dropped directly into the cold aisle. Pressure sensors provide data that allow the velocity of the air handlers to be adjusted in response to changes.
How much air moves through this facility? NetApp says that if all the air-handling units in the RTP data center were turned on full speed, it could inflate the MetLife blimp in about one second. Its capacity is equivalent to that of a 100-story office building.
The temperature in the second floor is controlled through relief dampers (shown below) that access a side air corridor for waste heat emerging from the first-floor hot aisle. As the hot air rises, it can either exit the building or be introduced into the second floor through the relief dampers.
The Aisle of Data Halls
Each door of this central hallway leads to a server room
The first floor of the NetApp data center houses the server area. Rather than an open floor, NetApp’s design features a series of enclosed data rooms that are accessible through a center entrance hallway (pictured above). Each data room uses cold-aisle containment and overhead air distribution. Instead of pumping cold air up through raised floors, overhead air distribution takes advantage of cold/hot air buoyancy and eliminates ductwork, which reduces energy needed for fans. This also reduces construction costs as raised floors are expensive to build.
The cold aisle in the server rooms of the NetApp data center in Research Triangle Park
The NetApp Research Triangle data center houses 36,000 square feet of data center space supporting 2,166 racks of equipment with a designed power load of nearly 25megawatts. That includes 1,800 racks for NetApp’s engineering labs running at loads of 12 kilowatts per rack, another 360 racks supporting the company’s IT operations and operating at 6 kilowatts a cabinet, and 30 network racks at 3 kilowatts per rack.
NetApp uses cold aisle containment, which separates the cold supply air from hot waste heat to maximize the benefits of free cooling. The system is designed to control the pressure of the supply air to ensure that it flows through the equipment and into the hot aisle.
The air supply temperature for the racks is set to 74 degrees. Elevating the temperature of the supply air allows NetApp to also raise the temperature set point for its chillers, saving energy and creating a cascading benefit. Air from the hot aisle is channeled to a side plenum where it can either be used to warm other parts of the building or vented to the outside.
The hot aisle in the NetApp data center