Hardware Reference
In-Depth Information
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, these drives can operate at any altitude and can withstand extremes of shock and
temperature. The drives are designed for military and industrial applications, such as systems used
aboard aircraft and in extremely harsh environments. They are, of course, more expensive than typical
hard drives that operate under ambient pressures.
Hard Disk Temperature Acclimation
Because most hard drives have a filtered port to bleed air into or out of the HDA, moisture can enter
the drive, and after some period, it must be assumed that the humidity inside any 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 condensation 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 especially 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 9.10 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 result. Place this package in the
operating environment for the time duration according to the temperature chart.
Table 9.10. HDD Environmental Acclimation Table
As you can see from this table, you must place an HDD that has been stored in a colder-than-normal
environment into its normal operating environment for a specified amount of time to allow it to
acclimate before you power it on.
Spindle Motors
The motor that spins the platters is called the spindle motor because it is connected to the spindle
around which the platters revolve. Spindle motors in HDDs are always connected directly; no belts
or gears are involved. The motor must be free of noise and vibration; otherwise, it can transmit a
rumble to the platters, which can disrupt reading and writing operations.
The spindle motor also must be precisely controlled for speed. The platters in HDDs revolve at
 
 
 
 
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