Definitive RN314 cooling guide

Hi All,

I wanted to post this to assist anyone else who was/is in the same position as me, concerned over the high HDD temps in their 314 (or other Atom based) ReadyNAS and not quite understanding the relationship between the fan speed and temps.
I live in Singapore where the ambient temp is a pretty steady 27 Celsius (80F) so I’m already at a bit of a disadvantage when it comes to keeping things cool.

I have a combination of drives in my unit and was concerned that some of the drives were approaching 50c at idle. Specifically a 3TB WD Se and 3TB WD Red Pro. The max operating temp for these drives is 55c, so 50c is a bit too close to that for my liking
This paper from 2012 also provides support to the notion that higher HDD temperatures have a direct correlation to failure rates: http://www.cs.virginia.edu/~gurumurthi/ ... mtos13.pdf

What I did:
1) Using the instructions for the RN104 found here: viewtopic.php?f=11&t=76184&hilit=fan+control#p424296
I control the fan with this script instead of the internal logic. Credit to user Moseleypj for the original scripting

But I have updated the script to reference the different data sources. Use the instructions in the above link but replace with the code below in the fanoveride file

  
  #!/bin/bash

    ## Variables ##
    FANPWMPATH=/sys/devices/platform/it87.2560/pwm1
    FANSPEEDPATH=/sys/devices/platform/it87.2560/fan1_input
    CORETEMPPATH=/sys/devices/platform/coretemp.0/temp2_input
    MAXFAN=100   # Maximum operable speed
    MINFAN=0     # Minimum operable speed
    MINPWM=140   # PWM Limit
    MAXPWM=255   # PWM Limit
    MINTEMP=40000   # Min temp -> Fan slowest
    MAXTEMP=65000   # Max temp -> Fan fastest
    NEWSPEED=50  # Initial fan speed (%)

    ## Functions ##
    function getReadings {
        FANPWM=$(cat $FANPWMPATH)
        FANSPEED=$(cat $FANSPEEDPATH)
        CORETEMP=$(cat $CORETEMPPATH)
    }

    function setFanSpeed {
        if [ $NEWSPEED -lt $MINFAN ]; then
            NEWSPEED=$MINFAN
        fi
        if [ $NEWSPEED -gt $MAXFAN ]; then
            NEWSPEED=$MAXFAN
        fi
        NEWPWM=$(expr $MAXPWM - $MINPWM)
        NEWPWM=$(expr $NEWPWM \* $NEWSPEED)
        NEWPWM=$(expr $NEWPWM / 100)
        NEWPWM=$(expr $NEWPWM + $MINPWM)

        echo $NEWPWM > /sys/devices/platform/it87.2560/pwm1
       }

    function calcFanPercent {
        TEMPRAN=$(expr $MAXTEMP - $MINTEMP)
        TEMPREL=$(expr $CORETEMP - $MINTEMP)
        TEMPREL=$(expr $TEMPREL \* 100)
        TEMPPER=$(expr $TEMPREL / $TEMPRAN)
        NEWSPEED=$TEMPPER
    }

    ###################################################################
    echo "Automatically controlling fan speed..."
    while true
    do
        getReadings
        echo "Temp: $CORETEMP C    FAN: $NEWSPEED% [$FANSPEED RPM] [$FANPWM]"

        calcFanPercent
        setFanSpeed

        sleep 10
    done
    ###################################################################

regarding automatic startup, the script doesn't start up automatically using the commands from the original post. If anyone knows how to fix this, please let me know. I just start it whenever i reboot and all is good.
If you want to change the noise profile, I found the best/easiest way to do this is by increasing the MINPWM value, which is just the slowest the fan will ever spin.


2) I purchased a 92-120mm adaptor and a 120mm corsair high static pressure fan to replace the stock fan. I tried a number of different fans (https://www.sugarsync.com/pf/D6435809_643_316563842) but the 314 chassis is so airflow restrictive that any fans focused on airflow (not static pressure made little if any difference)

Here's what it looks like:
https://www.sugarsync.com/pf/D6435809_643_318064764
https://www.sugarsync.com/pf/D6435809_643_318064773

The results:
After tweaking for noise/cooling, my HDDs which used to run @ 49-50c idle are now held at a steady 39-41c under any load.
There is some increased noise but I live in an areas with road noise so I can't tell.


Recommendations to Netgear:
The 3 series are aimed at SOHO/SMB usage. I think they should be able to adequately handle 720rpm SMB focussed HDDs without approaching those drives’ maximum operating temperature, which my 314 unit doesn’t seem to be able to do.

1) Increase the spacing between HDD cages of the 314. The chassis of the 314 seems to be too restrictive in terms of airflow. Particularly through the front of the HDD caddy’s. Consider increasing the spacing by just 1-2mm. This won’t add much to the dimensions of the unit.
2) Replace the 92mm fan with a 120mm higher static pressure fan. There is room for this considering the bottom rear panel is basically just a blanking plate.
3) Give users a high-mid-low setting in the software for the fan performance.
4) Change the fan control algorithm so it starts at a higher speed and doesn’t wait until the disks get to too high a temp before increasing fan speed.