Hardware Reference
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covered internally by this breather filter. Some drives use even finer grade filter elements
to keep out even smaller particles.
I conducted a seminar in Hawaii several years ago, and several of the students were from
one of the astronomical observatories atop Mauna Kea. They indicated that virtually all
the HDDs they had tried to use at the observatory site had failed quickly, if they worked
at all. This was no surprise because the observatories are at the 13,796-foot peak of the
mountain, and at that altitude, even people don't function well! At the time, they had to
resort to SSDs, tape drives, or even floppy disk drives as their primary storage medium.
Some manufacturers produce drives that are hermetically sealed (airtight), although they
do still have air inside the HDA. Because they carry their own internal air under pressure,
thesedrivescanoperateatanyaltitudeandcanwithstandextremesofshockandtemperat-
ure. The drives are designed for military and industrial applications, such as systems used
aboard aircraft and in extremely harsh environments. They are, ofcourse, more expensive
than typical hard drives that operate under ambient pressures.
Hard Disk Temperature Acclimation
BecausemostharddriveshaveafilteredporttobleedairintooroutoftheHDA,moisture
canenterthedrive,andaftersomeperiod,itmustbeassumedthatthehumidityinsideany
hard disk is similar to that outside the drive. Humidity can become a serious problem if
it is allowed to condense—and especially if you power up the drive while this condensa-
tion is present. Most hard disk manufacturers have specified procedures for acclimating a
hard drive to a new environment with different temperature and humidity ranges, and es-
pecially for bringing a drive into a warmer environment in which condensation can form.
This situation should be of special concern to users of laptop or portable systems. If you
leave a portable system in an automobile trunk during the winter, for example, it could be
catastrophic to bring the machine inside and power it up without allowing it to acclimate
to the temperature indoors.
The following text and Table 9.11 are taken from the factory packaging that Control Data
Corporation (later Imprimis and eventually Seagate) used to ship with its hard drives:
If you have just received or removed this unit from a climate with temperatures at or
below 50°F (10°C) do not open this container until the following conditions are met,
otherwise condensation could occur and damage to the device and/or media may res-
ult. Place this package in the operating environment for the time duration according
to the temperature chart.
Table 9.11 HDD Environmental Acclimation Table
 
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