Hot air exiting from the rear of the chassis is recirculated in the inlet air at the front of the chassis. High Temperature: [arg1], Low Temperature: [arg2].
The front of this chassis has multiple node and chassis ambient air temperature sensors. If the inlet air temperature range across all
these sensors becomes greater than the preset acceptable limit then this warning is triggered. This large inlet air temperature range
indicates that some components will become warmer which in turn will request for more cooling, consuming more fan power than necessary.
Alert Category
Chassis/System Management (Warning)
Chassis LED that is Lit
None
CIM Information
Prefix:CMM
and ID:0862
SNMP Trap ID
mmTrapChassisN
Automatically Notify Support
No
User Response
- First check to ensure the rack's sill-plate/rack-skirt/tilt-plate/baffle is installed at the front edge of the rack bottom. Common causes
for this event are due to either cold or hot air escaping from under the rack and reaching the bottom-most ambient temperature sensors.
If it is cold air that is the root cause, see last item.
- To pinpoint the area that is creating this large ambient air temperature range, access the CMM's web browser to view and record each node
and chassis ambient temperature readings. Note the physical locations of both the hottest and coldest ambient temperature readings.
These are the two areas that need to be more closely studied.Look for any openings that permit rack's hot exhaust air to recirculate to the rack front.
This can range from possible cable raceway caps being removed to missing filler/blank panels between servers and switches. In some cases, it was
observed that the current rack was properly sealed but the adjacent rack had openings allowing hot air from the exhaust aisle to
recirculate to rack front.
- Once the opening has been pinpointed, plug it to verify the event recovers by observing system health and the CMM event log. If the rack
configuration or datacenter layout does not permit the hot air from recirculating, then disable this event for the short term until a long term fix is implemented.
To disable this hot air recirculating event, select the "Chassis management" in the CMM's web browser. Select "Chassis" then choose
the "Temperature" tab followed by selecting the "Hot Air Recirculation" tab. Un-check the box and click "apply."
- Regarding the cold air escaping from under the rack situation, this condition will not drive fans to higher speeds. Instead this condition
reflects less than ideal sealing from the raised floor and rack cabling. Its recommended that the sealing is improved. However, if this
is not realistic, one can revert to simply turning off the hot air recirculation detection event as described above on the bottom-most chassis in the rack
to prevent this event. However, its still recommended to leave the hot air recirculation detection event enabled on the chassis above the bottom
chassis to monitor for other possible hot air recirculating causes.