Cooling |
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Active vs . Passive ; what to look for and how to choose
While an active system offers greater functionality than a passive system , the superiority of one over the other is contextual . Just like every runner must find what works best for them individually , knowing when to use active or passive airflow management is a decision that must be influenced by the specific needs of the data centre .
An active system uses pressure sensors to discern how quickly server fans spin . If pressure is increased , the system ’ s fans automatically increase to match it . This helps maintain a zeropressure environment in the cabinet to reduce the workload of the server fans . The result is electrical efficiency of the servers and minimal wear on their cooling components . As the number of servers and power consumption increase in a cabinet , so does the likelihood that airflow will become restricted and an active cooling system will be required .
Since active systems scale based on server loads and their associated cold-air consumption , they also help maintain proper airflow regardless of how far the cabinet
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In both active and passive configurations , the goal is the same : To get cool air to pass through critical rack equipment and move hot air into a return plenum using air containment . |
is from the source of cool air . This prevents problem areas that tend to occur in a passive system as the distance from the return grows .
An active air system :
• Uses integrated fans at the top or rear of the cabinet
• Works well with in high-density cabinet applications
• Prefers unrestricted airflow ( which is ideal ), but can function without it
• Utilises automatic fan speed adjustment based on air pressure
• Should be connected to the backup power source to allow for air movement in a power outage
On the other hand , the primary benefit of a passive system is simplicity . Unlike an active system , there are no additional cooling components involved in airflow management because the system relies exclusively on server fans . Fewer equipment purchases are necessary resulting in lower upfront costs . The inner-workings of a passive system are straightforward : Server fans draw in cool air to cool the components within the server . The cool air is then expelled out of the server as hot air . The hot air flows and rises into the return duct
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or plenum of the rack , row or room where it is eventually treated by a cooling system .
A passive air system :
• Relies on server fans to pull air through rack equipment and push air into the return plenum
• Works well in low-density cabinets
• Requires unrestricted airflow from the cabinet to the plenum
• Can be more energy efficient , since no additional fans are required
Making sense of it all
Bottom line is that one system isn ’ t inherently superior to the other . Data centre managers should typically choose a passive chimney system in low-density cabinets . However , as the global consumption of digital resources continues to increase , so too will the stress that is placed on data centres . As this happens , data centre density will inevitably scale up , escalating the need for active chimney systems . Ultimately , the goal is to make each data centre a better version of itself . And , in case you ’ re wondering , all my incremental training adjustments paid off . I survived my marathon and am looking forward to the next one .
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20 | August 2017 |