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AXP1406/AXP1600 Subsystem IPMI Programmer’s Reference (6806800B66C)
141
A System Behavior in Response to
Sensor Events
A.1 Introduction
This chapter introduces important information for those who are developing their own
applications code, based on how the Centellis 3406 and 3600 system behaves to different
events.
A.2 Cooling Management in Normal Operation Mode
The Shelf Manager operates in normal mode with respect to cooling if no temperature sensor
in the shelf reports crossing of one of the upper thresholds (noncritical, critical or
nonrecoverable). In that case, there is no need to accelerate the fan speed.
On the contrary, the Shelf Manager in normal mode periodically reduces the fan speed by
FAN_LEVEL_STEP_DOWN* levels (once per COOLING_FAN_DECREASE_TIMEOUT*
seconds) until the fan speed reaches the minimum fan level or the shelf goes to abnormal mode
(with at least one of the temperature sensors reporting one of its upper thresholds crossed).
The minimum fan level is initially specified as a configuration parameter, but its value is
adjusted if the transition to the abnormal mode happens, in order to prevent subsequent
recurrence of the thermal alert.
A.3 Cooling Management in Abnormal Operation
Mode
The Shelf Manager operates in abnormal mode with respect to cooling if at least one
temperature sensor in the shelf reports crossing of one of the upper thresholds (noncritical,
critical or nonrecoverable). In that case, the Shelf Manager takes over the control of all fan
trays, including those that support local control mode, but excluding any fans for which the Get
Fan Level command reports that the fan is in 'Emergency Shut Down' mode. The Shelf
Manager raises the fan speed by FAN_LEVEL_STEP_UP* levels for every fan tray every
COOLING_FAN_INCREASE_TIMEOUT* seconds until the temperature reported by all
temperature sensors falls below the thresholds.
Additionally, when at least one critical temperature threshold has been exceeded, the Shelf
Manager starts reducing the power level of FRUs one level each COOLING_POLL_TIMEOUT*
seconds, if possible. FRUs are not powered down in that case, for example, SetPowerLevel(0)
is not issued. In that state, the Shelf Manager also immediately raises the level of all fans to the
maximum level and keeps it at maximum.