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BLOG: Be green with higher ambient temperature

Kenny Sng | Aug. 5, 2011
Data centres are over-cooled. Clearly, a paradigm shift is needed.

I recall a conversation, not too long back, with my program manager who had embarked on his maiden LEAN - 6 Sigma certification, evangelising the omission of waste from a given process cycle.

This prompted me to think about organisational IT functions and what this currently entails. What in the process isn't useful? Without impacting deliverables, what can be reduced without compromising deliverables?

Today's cloud environment is hosted in mega data centres and many companies host their private cloud in their enterprise data centres. Power efficiency is at the heart of every leading company. Are our data centres designed correctly?

Walk into any data centre and you will find that it is running at 21 deg C to 22 deg C. Data centres are over-cooled, designed to run at maximum cooling temperatures. ASHRAE (American Society of Heating, Refrigeration and Air-conditioning Engineers) recommends temperatures in the high 30s Centigrade range for different classes.  Since 2006, ASHRAE operating guidelines advise running data centres at a temperature of 27 deg C (81 deg F). However, few data centre operators adhere to these guidelines as evidenced by service-level agreements (SLA) that state operating temperatures of 22 deg C. Clearly, a paradigm shift must precede any technical corrections.

Get the basics right

For now, let's get the basics right, starting with 27 deg C operations.  

What does running at 27 deg C actually mean? It refers to the supply temperature of the server intake cold aisle.

So is the solution as simple as increasing the operating temperature? Is that all that is necessary?

It is a misnomer that allowing the room to heat up will save on cooling costs.  Proper equipment cooling requires an engineered solution that adheres to Delta T specifications in terms of cooling tonnage and airflow. Data centres must be designed with proper cooling capacity for high density racks.  Air flow needs to be segregated properly - hot air in the hot aisle and cold air in the cold aisle - for a closed loop cooling path. It is essential to ensure sufficient airflow velocity to cool the equipment racks.

The Computer Room Air Conditioning (CRAC) must match the equipment heat load and, ensuring the Delta T temperature is met. Exceeding the Delta T specs has operational consequences so understanding the specs and how your DC performs is crucial in this respect.

What is the next step?

Once you've ensured your data centre is designed in accordance with basic cooling principles and IT equipment has cooled effectively, the next step is to raise the temperature from 21 deg C to 27 deg C.  This should be done progressively, raising the temperature one degree at a time.  You can change the sensor settings or switch off the Computer Fluid Dynamic (CFD) of the Computer Room Air Conditioning (CRAC).


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