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I had an argue with a colleague about :

  • "How do software programs (i.e. hwmonitor) determine the temperature of the hard drive?"

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I said that there must be a thermometer inside the HDD and the data (via SMART) is passed as regular info to the soft which wants that info .

He said : "No. There is no thermometer inside the HDD. You have to plug it as another hardware on your HDD. All the software uses statistics about heat from the RPM info"

  • How do software programs like hwmonitor, determine the temperature of the HDD?
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15  
Your colleague is completely clueless and foolish. –  barlop Apr 28 '13 at 22:44

3 Answers 3

up vote 32 down vote accepted

The hard drive has a temperature sensor (or multiple temperature sensors - they might be used for internal control, self-test etc...) inside, and this data is passed through SMART (in fact, this is a standardized SMART parameter).

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5  
Aye. OP could have found by just reading http://en.wikipedia.org/wiki/S.M.A.R.T., scrolling to parameter 190 ans searchinf for the word temperature. (E.g. open page, <kbd>Control</kbd>-<kbd>F</kbd>, temperature <kbd>Enter</kbd>). –  Hennes Apr 28 '13 at 20:00
1  
@Hennes I assumed it relates to SMART. wasn't so sure. and hence - did not look it under SMART category. –  Royi Namir Apr 28 '13 at 20:06
    
Now you have two links to show your colleague though. ;-) –  Hennes Apr 28 '13 at 20:07
2  
But by posting it on SO many of gets to be entertained, so it's not a waste. –  crdx May 3 '13 at 17:53

No, the temperature monitor is embedded into the HDD. It's a more recent addition and you will only see it with some of the newer SCSI disks. Anything older than a few years won't have the sensors.

It's actually a part of the S.M.A.R.T. suite that reports around 30 attributes. (http://www.hdsentinel.com/smart/index.php)

The software just pulls it from the hardware. You won the argument.

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I don't understand. SMART has been for years now. are you telling me that only the new drives has sensors ? I have a 5 years old drive which I can tell its temperature....please explain. –  Royi Namir Apr 28 '13 at 20:08
6  
It's an infrared thermometer. It's integrated in the hard drive. I used to have to replace them all the time when they used to have a high failure rate. They are pretty good now. Edit: Anything supporting SMART should have the thermometer integrated. 5 years old is not that bad. I'm talking about 10-15 years old. –  Will.Beninger Apr 28 '13 at 20:08
    
oh ok :-)....... –  Royi Namir Apr 28 '13 at 20:14
9  
Consumer hard drives started including temperature sensors in 2008. Before that, PCs typically had no hard drive temperature sensors and Macs typically had a sensor bonded to the outside of the drive. Modern drives have a sensor bonded to the inside of the drive casing. Last I checked, most hard drives used thermistors because there was no device already bonded to the inside of the case and a thermistor is cheap if used alone. SSDs typically use silicon bandgap temperature sensors integrated into the controller, cheap because no additional device is needed. –  David Schwartz Apr 28 '13 at 20:31

all the software uses statistics about heat from the RPM info"

Hard disk drives spin at a constant rate (usually 5400 RPM, 7200 RPM, 10000 RPM, or 15000 RPM). So the statistics on RPM info will probably be of little value for determining temperature.

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2  
Obviously the higher the RPM the cooler the drive is, since the faster-spinning platters fling the heat off of the surface with much greater force than the slower platters. /s –  Justin ᚅᚔᚈᚄᚒᚔ Apr 29 '13 at 15:51
    
@Justinᚅᚔᚈᚄᚒᚔ I would upvote that, but I'm afraid that future visitors might think you're serious. :) –  Moshe Katz Apr 29 '13 at 19:36

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