Fan control from http://lime-technology.com/forum/index.php?topic=5548.105

unraid-fan-speed.sh

#!/bin/bash
# unraid_array_fan.sh v0.5 
# v0.1: By xamindar: First try at it.
# v0.2: Made a small change so the fan speed on low doesn't fluctuate every time the script is run.
# v0.3: It will now enable fan speed change before trying to change it. I missed 
#        it at first because pwmconfig was doing it for me while I was testing the fan.
# v0.4: Corrected temp reading to "Temperature_Celsius" as my new Seagate drive
#        was returning two numbers with just "Temperature".
# v0.5: By Pauven:  Added linear PWM logic to slowly ramp speed when fan is between HIGH and OFF.
# A simple script to check for the highest hard disk temperatures in an array
# or backplane and then set the fan to an apropriate speed. Fan needs to be connected
# to motherboard with pwm support, not array.
# DEPENDS ON:grep,awk,smartctl,hdparm

### VARIABLES FOR USER TO SET ###
# Amount of drives in the array. Make sure it matches the amount you filled out below.
NUM_OF_DRIVES=15

# unRAID drives that are in the array/backplane of the fan we need to control
HD[1]=/dev/sdb
HD[2]=/dev/sdc
HD[3]=/dev/sdd
HD[4]=/dev/sde
HD[5]=/dev/sdf
HD[6]=/dev/sdg
HD[7]=/dev/sdh
HD[8]=/dev/sdi
HD[9]=/dev/sdj
HD[10]=/dev/sdk
HD[11]=/dev/sdl
HD[12]=/dev/sdm
HD[13]=/dev/sdn
HD[14]=/dev/sdo
HD[15]=/dev/sdp
#HD[16]=/dev/sdq
#HD[17]=/dev/sdr
#HD[18]=/dev/sds
#HD[19]=/dev/sdt
#HD[20]=/dev/sdu
#HD[21]=/dev/sdv
#HD[22]=/dev/sdw
#HD[23]=/dev/sdx
#HD[24]=/dev/sdy

# Temperatures to change fan speed at
# Any temp between OFF and HIGH will cause fan to run on low speed setting 
FAN_OFF_TEMP=30     # Anything this number and below - fan is off
FAN_HIGH_TEMP=40    # Anything this number or above - fan is high speed

# Fan speed settings. Run pwmconfig (part of the lm_sensors package) to determine 
# what numbers you want to use for your fan pwm settings. Should not need to
# change the OFF variable, only the LOW and maybe also HIGH to what you desire.
# Any real number between 0 and 255.
#
# FAN_OFF_PWM=100
# FAN_LOW_PWM=150
# FAN_HIGH_PWM=255
FAN_OFF_PWM=70
FAN_LOW_PWM=80
FAN_HIGH_PWM=255


# Fan device. Depends on your system. pwmconfig can help with finding this out. 
# pwm1 is usually the cpu fan. You can "cat /sys/class/hwmon/hwmon0/device/fan1_input"
# or fan2_input and so on to see the current rpm of the fan. If 0 then fan is off or 
# there is no fan connected or motherboard can't read rpm of fan.
# ARRAY_FAN=/sys/class/hwmon/hwmon1/device/pwm2
ARRAY_FAN=/sys/class/hwmon/hwmon1/device/pwm2

### END USER SET VARIABLES ###


# Program variables - do not modify
HIGHEST_TEMP=0
CURRENT_DRIVE=1
CURRENT_TEMP=0

# Linear PWM Logic Variables - do not modify
NUM_STEPS=$((FAN_HIGH_TEMP - FAN_OFF_TEMP - 1))
PWM_INCREMENT=$(( (FAN_HIGH_PWM - FAN_LOW_PWM) / NUM_STEPS))
echo "Linear PWM Range is "$FAN_LOW_PWM" to "$FAN_HIGH_PWM" in "$NUM_STEPS" increments of "$PWM_INCREMENT


# while loop to get the highest temperature of active drives. 
# If all are spun down then high temp will be set to 0.
while [ "$CURRENT_DRIVE" -le "$NUM_OF_DRIVES" ]
do
  SLEEPING=`hdparm -C ${HD[$CURRENT_DRIVE]} | grep -c standby`
  if [ "$SLEEPING" == "0" ]; then
    CURRENT_TEMP=`smartctl -d ata -A ${HD[$CURRENT_DRIVE]} | grep -m 1 -i Temperature_Celsius | awk '{print $10}'`
    if [ "$HIGHEST_TEMP" -le "$CURRENT_TEMP" ]; then
      HIGHEST_TEMP=$CURRENT_TEMP
    fi
  fi
#echo $CURRENT_TEMP
  let "CURRENT_DRIVE+=1"
done
echo "Highest temp is: "$HIGHEST_TEMP

# Enable speed change on this fan if not already
if [ "$ARRAY_FAN" != "1" ]; then
  echo 1 > "${ARRAY_FAN}_enable"
fi

# Set the fan speed based on highest temperature
if [ "$HIGHEST_TEMP" -le "$FAN_OFF_TEMP" ]; then
  # set fan to off
  echo $FAN_OFF_PWM  > $ARRAY_FAN
  echo "Setting pwm to: "$FAN_OFF_PWM
  elif [ "$HIGHEST_TEMP" -ge "$FAN_HIGH_TEMP" ]; then
    # set fan to full speed
    echo $FAN_HIGH_PWM > $ARRAY_FAN
    echo "Setting pwm to: "$FAN_HIGH_PWM
  else
    CURRENT_SPEED=`cat $ARRAY_FAN`
    # set fan to full speed first to make sure it spins up then change it to low setting.
    if [ "$CURRENT_SPEED" -lt "$FAN_LOW_PWM" ]; then
      echo $FAN_HIGH_PWM > $ARRAY_FAN
      sleep 2
    fi
    # Calculate target fan PWM speed as a linear value between FAN_HIGH_PWM and FAN_LOW_PWM
    FAN_LINEAR_PWM=$(( ((HIGHEST_TEMP - FAN_OFF_TEMP - 1) * PWM_INCREMENT) + FAN_LOW_PWM))
    echo $FAN_LINEAR_PWM > $ARRAY_FAN
    echo "Setting pwm to: "$FAN_LINEAR_PWM
fi