Cisco MDS 9148V-K9 Hardware Installation Manual page 18

Power Supplies
Figure 5: PSU
To facilitate different data center cooling configurations of hot or cold aisles and racks, there are two models
of PSUs. The first type has airflow with port-side intake and exhaust at the rear of the chassis. The second
type has airflow in the opposite direction, that is, rear-chassis intake and port-side exhaust. The airflow direction
is denoted on each PSU as follows:
• Red—Port-side intake airflow
• Blue—Port-side exhaust airflow
The switch supports PSUs of only one airflow type at a time. Both PSUs have to be either port-side exhaust,
or port-side intake PSUs.
Note The direction of PSU airflow must match the direction of the fan module airflow.
For more information on installing and removing PSUs, see
Cisco MDS 9148V-K9 Switch Hardware Installation Guide
12
Overview of Cisco MDS 9148V-K9 Switch
Installing and Removing Power Supply Units.