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  1. #21
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    Quote Originally Posted by ashiekh View Post
    Concerning hard drives

    https://www.zdnet.com/article/heat-d...res-what-does/

    "
    Relative humidity is the major reliability factor - more so than temperature
    "

    "
    High temperatures are not harmless, but are much less significant than other factors.
    "
    See Google's study : Failure Trends in a Large Disk Drive Population : https://static.googleusercontent.com...k_failures.pdf

    tldr:
    * hard drives will fail more often at colder temperatures
    * hard drives that are older than 3-4 years of 24/7 or near 24/7 usage have a much higher failure rate if used at high temperatures (40c+)



    3.4 Temperature

    Temperature is often quoted as the most important environmental factor affecting disk drive reliability. Previous studies have indicated that temperature deltas as low as
    15C can nearly double disk drive failure rates [4]. Here we take temperature readings from the SMART records every few minutes during the entire 9-month window
    of observation and try to understand the correlation between temperature levels and failure rates.
    We have aggregated temperature readings in several different ways, including averages, maxima, fraction of time spent above a given temperature value, number of
    times a temperature threshold is crossed, and last temperature before failure. Here we report data on averages and note that other aggregation forms have shown similar trends and and therefore suggest the same conclusions.
    We first look at the correlation between average temperature during the observation period and failure. Figure 4 shows the distribution of drives with average temperature
    in increments of one degree and the corresponding annualized failure rates. The figure shows that failures do not increase when the average temperature increases.
    In fact, there is a clear trend showing that lower temperatures are associated with higher failure rates.
    Only at very high temperatures is there a slight reversal of this trend.
    Figure 5 looks at the average temperatures for different age groups. The distributions are in sync with Figure 4 showing a mostly flat failure rate at mid-range temperatures
    and a modest increase at the low end of the temperature distribution. What stands out are the 3 and 4-year old drives, where the trend for higher failures with
    higher temperature is much more constant and also more pronounced
    .
    Overall our experiments can confirm previously reported temperature effects only for the high end of our temperature range and especially for older drives. In the lower and middle temperature ranges, higher temperatures
    are not associated with higher failure rates. This is a fairly surprising result, which could indicate that datacenter or server designers have more freedom than previously thought when setting operating temperatures for
    equipment that contains disk drives. We can conclude that at moderate temperature ranges it is likely that there are other effects which affect failure rates much more strongly than temperatures do.
    temps.gif

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    ashiekh (05-24-2019), ehume (05-24-2019)

  3. #22
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    Interesting; I wonder how much of the low temperature failure is really due to humidity? i.e. the relative humidity increases as one cools the air.

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    Quote Originally Posted by ashiekh View Post
    Interesting; I wonder how much of the low temperature failure is really due to humidity? i.e. the relative humidity increases as one cools the air.
    Altitude as well.

    When we write our PSU PRDs, we define operating temperature range, operating RH range and max operating altitude.

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    https://www.psma.com/sites/default/f...plications.pdf

    In China, you're required to label your electronics with maximum operating altitude when your product won't work at full potential at 5000M. If the product works as advertised at 5000M, you don't need any logo.

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    Interesting; I wonder how much of the low temperature failure is really due to humidity? i.e. the relative humidity increases as one cools the air.
    None

    Its really because of the Temperature.
    Because we are talking about an oil based bearing.

    And what do you know about oil based bearings?

    Hint: Think about cars. And what happens there if the oil is cold. Its safe to assume that the same happens with Harddrives and that's what kills it.
    That's why there is such a high failure rate for "too cold"

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    Quote Originally Posted by Stefan Payne View Post
    And what do you know about oil based bearings?

    Hint: Think about cars. And what happens there if the oil is cold. Its safe to assume that the same happens with Harddrives and that's what kills it.

    I have taken a course in Tribology, although it was not very enlightening.

    The problem with cold oil in cars is distribution; in this case the oil is already at the bearing.
    Last edited by ashiekh; 05-25-2019 at 11:32 AM.

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