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Adaptive Adjustment of the Minimum Fan Level System Behavior in Response to Sensor Events
AXP1406/AXP1600 Subsystem IPMI Programmer’s Reference (6806800B66C)
143
The following graph illustrates the behavior of the above cooling algorithm in finding a stable
fan level in real shelf, in the presence of a substantial thermal load in the shelf. The
configuration parameter NORMAL_STABLE_TIME* is set to 30 minutes. The graph presents
the fan speed changes over a period of 70 minutes. The horizontal axis has time scaled from 0
to 70 minutes.
The fan speed is initially lowered to 3. This causes a thermal alert and after a single increase
in fan speed, during the subsequent fan speed reduction, the level stabilizes at 4. After the
expiration of a period defined by the parameter NORMAL_STABLE_TIME* (which is equal to
30 minutes) the level is lowered to 3 which again causes a thermal alert, an increase in fan
speed with subsequent reductions, and the fan level again stabilizes at 4.
* These are configurable options in /etc/shelfman.conf. If these values are not defined in
shelfman.conf, default levels are used.
Figure A-1 Cooling Algorithm