The Difference Between Active and Passive Exhaust - and What it Means to Your Data Center

The Difference Between Active and Passive Exhaust - and What it Means to Your Data Center

Maintaining allowable temperatures accounts for 40 percent of all the energy used in a data center.

Data center operators must therefore take every measure to ensure that cooling and airflow within a facility is optimized. A good starting point is understanding the difference between active and passive systems, and knowing which is right for your facility.

Passive Cooling

  • Relies on server fans to draw cool air into equipment, and expels hot exhaust through containment chambers connected to the return plenum.
  • Works well in low-density cabinets
  • Helps realize energy efficiency since no additional cooling infrastructure is required for airflow management
  • Requires completely unrestricted airflow, which means orderly cable arrangements

Active Cooling

  • Relies on fanst integrated at the rear and/or tops of cabinets
  • Automatically adjusts fan speeds according to server load, thereby
    • Eliminating hot spots caused by distance from the cool air source
    • Lessening wear on servers over time
    • Ensuring temperatures stay within an allowable range
  • Is connected to the UPS, and will continue to function in an outage
  • Expels hot exhaust through containment chambers connected to the return plenum
  • Works well in high-density cabinets, but is not energy-efficient for low-density cabinets
  • Completely unrestricted server airflow is ideal, but can fasibly function without it

Which is Right for You?

Every situation is unique, but for low-density cabinets, passive air is generally the way to go. It uses less energy, but is effective enough to optimize cooling efficiency.

For high-density cabinets, or in any situation where airflow is restricted, use and active system like Geist ActiveAir™. It will preclude having to increase the CRAC output as a result of poor airflow.

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