Cooling Efficiency in Data Centers Leads to Increased Temperature Sensor Density
by Jeff Fitch, SynapSense Director of Product Management
Why would data center cooling efficiency require more sensors than you might expect? Is it important how many sensors are monitoring temperature in a data center? The evolution of environmental monitoring in the data center tells us why. A decade ago, a single sensor at shoulder height per 10,000 square feet was considered sufficient. Thermal issues were solved by over-cooling. With cooling energy running at 30% to 50% of total data center energy, the most obvious place to save is the cooling energy.
As data center operators increase set points and reduce fans speeds to improve efficiency, concerns over thermal issues reappear. Now a single temperature sensor is no longer adequate. But how many sensors are needed? One every rack? One every aisle? The answer is, it depends. At SynapSense, our air flow analysts suggest the following characteristics of the data center are what it depends upon:
- Temperature threshold at which the system will run
- Dynamics of the IT load
- Sub-floor obstructions
- Mixed load IT equipment across the floor
- Highly concentrated IT load
- Equipment with unique air flow requirements
- Physical equipment layout – hot and cold aisles
Increased sensor density is necessary to mitigate risk. More risk factors equate to more sensors. Environmental monitoring systems, like SynapSense, provide a tool to enable data center operators to reduce their energy usage while maintaining the reliability margin that was once the purview of over-cooling. After deploying millions of square feet of data center environmental monitoring, SynapSense has caught highly localized thermal events using our recommended sensor density. Configurations range from every rack to several per aisle, and from three sensors on the rack intake (ASHRAE recommendation) to a single sensor at the top server inlet. Networks of dense sensors are replacing the former practice of over-cooling data centers, resulting in greater reliability. Monitoring replaces the over-cooling buffer that energy efficiency removes. The correct sensor density can be determined by a SynapSense air flow analyst and is required to restore the reliability that was once only available by over-cooling.