Wednesday, June 20, 2012
3 essentials for energy-efficient data centers
By Padma Nagappan
Published June 18, 2012
When it comes to data centers and energy efficiency, companies prefer to take their own unique approach. Google has its custom servers and built-in batteries, Facebook has opted for an evaporative cooling and proprietary uninterruptible power supply and Yahoo has selected an outdoor air-cooled "chicken coop" design.
Large data center operators have an inherent advantage when implementing energy-efficient strategies as they can shift operations to another facility in the event of a failure or changing circumstances, according to Michael Fluegeman, a principal and engineer with PlanNet Consulting. PlanNet is a Brea, Calif.-based IT consulting firm focused on providing support for critical infrastructure, including data centers.
"Large centers can operate at a higher risk of failure with the offset, but smaller data centers can't do that as easily," said Fluegeman, who specializes in facilities, power and cooling.
"It's following the sun or the moon, because they can very easily shift their traffic to different locations depending on whether it's night or day in a particular location," he said. "Especially if you're using outside air and free cooling or air-side economy as it's called, this is a concept that's used to some degree by larger companies with data centers worldwide, where they shift traffic."
So how can data centers lacking the resources of their larger counterparts achieve increased energy efficiency while reducing costs?
According to Fluegeman, there are three essentials that smaller data centers should follow.
Essential #1: Start with the IT architecture: Fluegeman suggests starting with how you structure all the different components for a network or data center, as there are ways to create a design that will work more efficiently with certain tasks such as file duplication.
"There are ways to architect your system to deal with duplication and keep things lean and mean and trim with good housekeeping,” he said. “This allows data centers to be smaller and greener by using as little power as possible."
As an example, Fluegeman referred to how many have moved away from Microsoft Outlook email in preference of cloud-based email such as Gmail. With Outlook, the same file can get stored hundreds of times, taking up valuable server space. Email in the cloud saves and stores a file only once.
Tiered storage is another way to lower energy usage.
Using this method, older data is stored in a way that takes up very little energy by archiving them on a storage device that goes to sleep or can be pulled up as needed.
Photo of Facebook's data center in Prineville, Ore. provided by Tom Raftery via Wikimedia Commons
Essential #2: Rethink the cooling strategy: Even for smaller data centers, the current trend is to use either a hot aisle containment method or a cold aisle containment method, which arranges the equipment so that hot air is isolated from the cold air.
Containing the hot air and cold air separately and preventing them from mixing can create a 30-degree difference in temperature, according to Fluegeman. The big difference is easier for the A/C system to sense, which results in less power needed to cool the area.
But how do you keep the two from mixing?
Hot air comes out the back, so you line up the servers so all the fronts face one direction and all the backs face the reverse direction. This creates a hot aisle and a cold aisle.
If a center has several parallel rows of servers, alternate hot and cold aisles can be set up by arranging the rows so the fronts face each other and back up to another line of servers, like houses on parallel streets.
Essential #3: Reduce power used with offline uninterrupted power supply, fewer transformers and higher voltage: A radical transformation in data centers is to use an offline uninterrupted power supply, or UPS. The UPS -- which acts as an emergency power supply in the case of a power failure -- also enables the center to operate more efficiently, according to Fluegeman, because it remains in a sleep mode and only wakes up if the power fails.
"It’s controversial -- some won't do it, but we encourage our clients to do it," Fluegeman said.
The lag between power outage and the UPS turning back on is so minimal that the equipment does not pick up on the drop in power, he said.
How the users operate the system will also impact efficiency. The high efficiency or economy mode carries a risk where as the low efficiency mode is considered more reliable, which Fluegeman characterizes as the classic compromise between cautious safety and efficiency.
In the same vein, reducing the number of transformers used will lower the amount of UPS used, which some engineers believe increases risk. Fluegeman, however, said that he thinks the risk is miniscule. A transformer provides isolation between input and output, which can be achieved with circuit breakers and other tools, he said.
Switching to higher voltage equipment can deliver significant energy savings, since it's more efficient and the physical conductors are smaller, something the U.S. is realizing now. While the rest of the world uses 240 volt power, U.S. equipment runs at 120 volts.
"If you look at power lines on big poles on the hill side, those wires are small -- they're far apart, but the power voltage is very high,” he said. “This is being applied to data centers now. Higher voltage is slightly more dangerous and in the U.S we have a lot more attorneys. That's what keeps voltage lower, in my personal opinion."