Each S11 or S31 Node base enclosure and each expansion enclosure in an S11, S31, or S32 Node has four rear fans that cool the main bay and two controller-bay fans that cool the controller bay. For effective cooling in each bay, the applicable cover must be on the enclosure. At any given time, an enclosure can tolerate at most a single fan failure in one bay or concurrent single fan failures in the main bay and controller bay. Fans can be replaced without interrupting service as long as at least one fan in the applicable bay remains running.
Each S32 Node base enclosure has two redundant power and cooling modules, each of which consists of a power supply and a fan. At any given time, an enclosure can tolerate at most a single power and cooling module failure. A single power and cooling module can be replaced without interrupting service.
The airflow in S11 and S31 Node base enclosures and in all expansion enclosures is from front to back in both the main bay and the controller bay. Similarly, the airflow in an S32 Node base enclosure is from front to back.
To ensure proper airflow, the air pressure at the front of an enclosure must be greater than the air pressure at the rear of the enclosure. The back pressure created by the rear rack door or other obstacles must not exceed 5 Pa (0.5mm H20).