Systems Manual

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=====Limulus Fan Control=====

There are two fans that pull air from under the case. The fans are directly under the blades and ensure there is adequate airflow to the blade CPUs.

The fans are connected to a single main motherboard auxiliary fan connector using a "Y" power splitter. A daemon, called ''limfanctl'' reads the blade temperatures and adjusts the fan speeds (based on the highest blade temperature) using a specifically configured ''fancontrol'' daemon (part of the the lm_sensors package). The ''limfanctl'' daemon is managed by ''systemd'' and will automatically start and stop the ''fancontrol'' daemon.

In addition, the ''limfanctl'' will monitor individual node CPU temperatures and if they exceed a user defined threshold (see below), the processor turbo-mode is turned off until the temperature goes below the threshold. 

Individual processor fan speeds are controlled by the node motherboard BIOS. 

The file ''/etc/limfanctl/limfanctl.conf'' can be uses to set the turbo-mode throttling. The settings are described in the ''limfanctl.conf'' file reproduced below. A debug log can be enabled by setting the ''DEBUG'' variable. 

<code>
# Parameters for Limulus Fan Control Daemon
# Changes in these settings may cause the worker nodes to overheat.
# Messages from limfanctl are placed in the system log file
# See /var/log/messages

# Set the worker node turbo control to automatic.
# If the THRESHOLD temperature is exceeded, the turbo mode on
# the worker nodes is disabled. Turbo mode is turned back on
# when the temperature goes below THRESHOLD.
# Note, this setting will override the node-turbo-on
# and node-turbo-off commands.
# Acceptable options "off" and "on." The default is "on."
AUTO="on"

# Set the threshold for when turbo mode is turned off on the
# worker nodes. Note, this does not ensure that overheating
# will not occur, it does help keep the temperatures more stable.
# Also, temperature values are in degrees C and multiplied by 1000
# Acceptable values must be a number, the default is 68000 (68 C).
THRESHOLD=78000

# To enable the debug log, change to DEBUG="1"
# The debug log location: /var/warewulf/Limulus/node-temp-debug.log
DEBUG=""
</code>
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