Tag: Data center


It’s cool and wet tonight, the perfect conditions for the creation of steam in our cooling plant. Below are a photos of the two cooling towers putting out steam and mist.

This equipment uses outside air to cool and compress freon, which is then piped inside to large air handlers in the data center. See our cooling system video for an overview.

Each of the cooling towers has 200 tons of cooling capacity, for a total of 400 RT (refrigeration tons) in the system. Either of the two towers can accommodate our current data center cooling requirement, so we have redundant capacity, allowing for failure or maintenance.

What’s 200 tons of cooling capacity mean? From Wikipedia:

The unit ton is used in refrigeration and air conditioning to measure heat absorption. Prior to the introduction of mechanical refrigeration, cooling was accomplished by delivering ice. Installing one ton of refrigeration replaced the daily delivery of one ton of ice.

In North America, a standard ton of refrigeration is 12,000 BTU/h = 200 BTU/min ≈ 3,517 W. This is approximately the power required to melt one short ton (2,000 lb) of ice at 0 °C in 24 hours, thus representing the delivery of 1 ton of ice per day.

So, if I’m doing my math right, with both towers at full capacity we could chill the equivalent of about one point four million watts. That would be an awful lot of trucks full of ice!

Rewinding power costs

Efficient datacenter cooling results

Efficient datacenter cooling results in reduced costs

Our green datacenter cooling system has established a great track record since deployment. Our 2008 total utility costs are projected to come in very near 2006 levels, despite huge growth of equipment in the datacenter.

So, more servers in 2008, but far less power used to cool them. That is green and cost effective! Our growth in power consumption is ongoing, but the trend line has taken a nice step downward due to the investment in efficiency.

For more info on the innovative Bell Products Core4 system at Sonic.net, see this article.

Critical systems: Power backup

Crossed wires shorting out, Troy, Illinois. Af...Image via Wikipedia

Obviously, an ISP doesn’t function without electricity, so we’ve got big investments in redundant power here.

A datacenter power system consists of multiple inputs which are arbitrated by a transfer switch, and multiple loads such as UPS systems and air conditioners (CRACs).

The primary input is PG&E, and the transfer switch monitors the quality of this input. If the utility power goes offline or fades, the transfer switch sends a signal to the starter on the generator, which powers up automatically. Once the generator power output is online and stable, which typically takes twenty to thirty seconds, the transfer switch physically swings a huge set of contacts over to the new input, transferring the load.

The UPS systems and their batteries carry the datacenter computing load during this startup and transfer, while CRAC loads are dropped during the transition. A datacenter can’t function for long without cooling, so the entire generator and transfer switch system must function as designed in order to stay online.

The generator itself is the really cool bit of this whole setup. For those who are into engines, it’s a 24 liter V-12 Detroit Diesel, with twin turbochargers. That’s a full two liters of per cylinder – imagine a piston and cylinder the size of a 2 liter soda bottle. Now, gang up twelve of them. It’s a huge engine. At full throttle it generates over one thousand horsepower, and three quarters of a megawatt of power.

In our five years at our Apollo Way location, the generator has only been called on to respond to a power outage twice. PG&E has done a great job for us, delivering quite reliable power. But, we still must test fire the generator once every week, top up it’s fuel every few months, and trade out old fuel for new periodically. It’s full generating capacity is totally load tested every few years by hooking it up to a massive resistor/heater bank. The maintenance and load testing is critical to assure that the power will be there when we do need it.

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