Breaking free from Internet hosting standards and pragmatism are the key to energy efficiency
After power, cooling servers are usually the most important cost center, electricity-wise, for hosting providers. But, at OVH.com, the cooling system only uses variable frequency fans and water pumps. In the RBX4 datacenter, which has been running for more than a year, the PUE (from the 20,000 V high-tension entry point to the servers’ control panels) varies between 1.16 and 1.09, which means that OVH.com is saving up to 50% on its total electricity bill (including the servers’ consumption), compared to traditional datacenters.
It is not free cooling, in the commonly used sense, but directly cooling servers with outside air.
In this optimal management of airflow, the construction of the datacenter itself plays a crucial part. The building is shaped like a tower, hollow in its center, with servers lined against the four interior walls. The n, air comes in through the face-walls, and is then discharged in the center of the tower, creating a chimney effect.
No piping is necessary to conduct the air. Because of the tower concept, cool air comes in directly to the servers’ face-walls, therefore regulating the fans’and the machines air inlets’ temperature.
The geographical location of the datacenters is also a very important aspect because regions north of the 45th parallel offer more temperate summers. So, even during summer, outside air can dissipate the heat of server’s components (hard drives, for instance). In case of temperatures reaching over 91°F, air atomizing can bring it back under 86°F.
On top of optimizing the flow, the tower concept is also very economical. No air conditioning equipment is required in the tower for the temperate climate in Beauharnois and North of France. The temperature inside the tower is always maintained at, at least, 68°F.
The industrialization of liquid cooling
This outside air-cooling system can only reach optimal performance levels when paired with the servers’ liquid cooling system. One of the key elements of OVH.com’s strategy for energy efficiency is the industrial development of water-cooling systems.
This idea, conceptualized in 2003 and a novelty in this industry at the time, consists of using liquid at the very center of the servers to cool down the processors. Each server is equipped of at least two tubes, one for the input and the other for the liquid output. That liquid is brought in heat exchangers, on top of processors and other components that generate a lot of heat (like motherboard chipsets). These heat exchangers, called “water-block”, essentially replace the usual air coolers. 70% of the heat generated by a server is then absorbed by the liquid, which has a coolant capacity far superior than air.
Depending on the location of the datacenters, the liquid can be cooled down by air through the use of cooling towers (similar to a car radiator system), or by thermal exchange with the water of a ground water table (as is the case of the P19 datacenter in Paris). The average temperature of the liquid is 95°F. Made of de-mineralized water, which is filtered and chemically controlled to prevent bacterial spread, the liquid runs through a closed circuit.
This liquid cooling system by itself divides by two the need in air conditioning (PUE below 1.5), which translates in huge savings on electricity.
In addition of lowering the energy costs and being environmentally friendly, the absence of air conditioners in our data centers considerably reduces the investment costs to build our infrastructures. In the end, this has favorable repercussions on the service prices we offer to our clients.
Finally, in an environmentally conscious effort, the BHS datacenter’s electricity is supplied by Beauharnois’ hydroelectric power plant, a clean and renewable energy source, located 300 meters away.