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The effect of temperature on
the reliability of IT installations
High ambient temperatures and the associated high component temperatures have a
deleterious effect on all technical products and thus also on IT installations.
The following areas are particularly affected:
• Functionality
The propagation time of electrical signals increases with temperature. If the tem-
perature increases beyond certain limits (at present approx. 100 °C crystal tempera-
ture) this will lead to malfunctions, particularly in the case of fast processors.
• Wear
Storage media, and in this case particularly magnetic tapes, suffer from wear due to
friction. The amount of wear increases with temperature, and beyond a certain point
(from about 45 °C tape temperature) it rises drastically.
• Failure rate and MTBF
The failure rate of a component, λ , is generally determined by mechanisms whose
reaction time increases when heated and thus at higher temperatures. This means
that the failure rate will also increase with temperature. The actual rate of increase
will depend on numerous additional factors, such as different component technology,
where the component is installed, and so on.
The measure of a system's reliability is generally given in terms of its MTBF (mean
time between failures), which is the reciprocal of the failure rate (MTBF = 1/ λ ). Ac-
cording to the information in the document MIL-HDBK-217F (Reliability Prediction of
Electronic Equipment. Department of Defense, Washington, D.C. 1990) the variation
with ambient temperature of the MTBF value for an IT installation follows the path
shown in the following diagram. This graph is normalized on the MTBF value at an
ambient temperature of 25 °C.
You can see from this diagram that increasing the ambient temperature by around
15 °C will halve the MTBF.
Relative MTBF depending on the ambient
140
120
100
80
60
40
20
0
15
Ambient temperature (°C)
U41644-J-Z816-5-76
temperature
25
35
45
Rel. MTBF
55
TEMPERATURE 1
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