{"id":3352,"date":"2017-05-24T17:02:46","date_gmt":"2017-05-25T00:02:46","guid":{"rendered":"http:\/\/kmwoley.com\/blog\/?p=3352"},"modified":"2017-05-24T17:08:12","modified_gmt":"2017-05-25T00:08:12","slug":"controlling-case-fans-based-on-hard-drive-temperature","status":"publish","type":"post","link":"https:\/\/kmwoley.com\/blog\/controlling-case-fans-based-on-hard-drive-temperature\/","title":{"rendered":"Controlling Case Fans Based on Hard Drive Temperature"},"content":{"rendered":"

I’ve always been annoyed that the fans in my server spin all the time (wasting power, making noise) when they’re not needed. The only reason they’re there is to cool my hard drives – which aren’t in use half the time.<\/p>\n

When switching to unRAID, I wanted to fix this. There is a plugin (Dynamix System AutoFan<\/a>) that is supposed to do this, but it didn’t work for me. In reading through several forum posts, I found a shell script that many people use to control their case fans based on their hard drive temperatures<\/a>. But it wasn’t straight forward to get it operating, so I thought I’d post the steps I followed to get it running.<\/p>\n

These instructions are specific to unRAID v6, but may be useful for other Linux installations.<\/p>\n

Discover your fan sensor kernel modules<\/h2>\n

By default, it’s likely that you don’t have the kernel modules installed to give the system access to your fan speed sensors. First we need to get that setup.<\/p>\n

    \n
  1. Install the NerdPack plugin<\/a>. It’s the easiest way to install Perl which is needed to discover your sensors.<\/li>\n
  2. SSH into your unRAID machine as root.<\/li>\n
  3. From the prompt, run\u00a0sensors-detect.\u00a0<\/em>Answer “Yes” (by pressing Enter) to every question except the last prompt- you do not need to automatically generate the config file.\n
    sensors-detect<\/pre>\n
    The output will be pretty long, and result in the something that looks like the following. Copy this block of text – you’ll need it in the next step.<\/p>\n
    #----cut here----\r\n# Chip drivers\r\nmodprobe coretemp\r\nmodprobe nct6775\r\n\/usr\/bin\/sensors -s\r\n#----cut here----<\/pre>\n
    Load the kernel modules at each boot<\/h2>\n<\/li>\n<\/ol>\n
    The\u00a0modprobe\u00a0<\/em>commands will load the specific kernel modules for your hardware enabling your computer to detect, read, and control these fans. But we want to make sure they run each time you boot your machine – to do that unRAID, we have to modify the ‘go’ file that runs each time your machine starts.<\/p>\n
      \n
    1. Open up your unRAID ‘go’ file in an editor\n
      nano \/boot\/config\/go<\/pre>\n<\/li>\n
    2. Take the lines that start with\u00a0modprobe<\/em>\u00a0from the\u00a0sensors-detect<\/em>\u00a0output and add them to your ‘go’\u00a0<\/em>file. Do not add in the ‘\/user\/bin\/sensors -s’ line.
      \n      \"\"<\/a><\/li>\n
    3. Save and quit nano (Ctrl-X, Yes)<\/em><\/li>\n
    4. Reboot your unRAID server. (Or, alternatively, you can run the\u00a0modprobe\u00a0<\/em>commands from the command line to load the kernel modules without rebooting).<\/li>\n<\/ol>\n
      After you reboot (or run the modprobe<\/em> commands), you can run the sensors<\/em> command from a command prompt which should show you the status of all the temperature sensors your machine knows about.<\/p>\n
      Figure out which controls what<\/h2>\n
      Next up, you’ll need to figure out which device controls what fan, as well as the minimum power that needs to be applied for a given fan to keep spinning.<\/p>\n
      Fans are controlled in Linux by assigning a value between 0 and 255 to the Pulse Width Modulated (PWM)<\/a>\u00a0fan header (0 is off, 255 is max power).<\/p>\n
      The\u00a0pwmconfig\u00a0<\/em>tool runs through all of your fan headers and vary the power output to find out which fans are controlled by each header.<\/p>\n
      To run it, SSH into your machine and run:<\/p>\n
      pwmconfig<\/pre>\n
      When prompted, answer “yes” to generating a detailed correlation.<\/p>\n
      When prompted to set up the configuration file, say “no”.<\/p>\n
      The output will be long.\u00a0What you’re looking for are the following things.<\/p>\n
      Testing pwm control hwmon2\/pwm1 ...\r\nhwmon2\/fan1_input ... speed was 1931 now 0\r\nIt appears that fan hwmon2\/fan1_input<\/strong>\r\nis controlled by pwm hwmon2\/pwm1<\/strong>\r\nWould you like to generate a detailed correlation (y)? y\r\nPWM 255 FAN 1925\r\nPWM 240 FAN 1859\r\nPWM 225 FAN 1748\r\nPWM 210 FAN 1648\r\nPWM 195 FAN 1535\r\nPWM 180 FAN 1415\r\nPWM 165 FAN 1306\r\nPWM 150 FAN 1184\r\nPWM 135 FAN 1063\r\nPWM 120 FAN 946\r\nPWM 105 FAN 826\r\nPWM 90 FAN 698\r\nPWM 75 FAN 0\r\nFan Stopped at PWM = 75<\/strong><\/pre>\n