Several major types of drive failures can be caused by excessive shock applied to the
drive, especially when it is in operation. This is not surprising, considering the way
hard disks work. When you have very precise read/write heads floating a millionth of an
inch above the surface of a smooth platter spinning thousands of revolutions per minute,
you shouldn't expect that you can give the device rough handling without consequences!
When the heads contact the surface of the platters, this is called a head slap
and each such event carries the potential for damage or data loss.
Despite the fragility of hard disk technology, we do expect to be able to
treat them, well, if not roughly, then at least without kid gloves. We want to put hard
disks into laptop computers and carry them around, or use removable drive trays, or
incorporate tiny hard disks into devices ranging from
handheld PCs to digital cameras. And even with desktop machines, we certainly don't expect
the drive to fail if we bump into the case while the PC is on, or similar minor mishaps
occur.
To address the increased needs for portability, and to improve reliability and reduce
sensitivity to shocks in a general way, hard disk manufacturers have been hard at work
improving the shock resistance of drives. One great way to do this would be to basically
pack cushioning material around the drive; unfortunately, this would create other
problems, ranging from needing to enlarge the drive's form factor, to making cooling more
difficult. Therefore, shock protection is primarily done by increasing the rigidity
of the most important components in the drive, such as the actuator
assembly and spindle motor. To reduce head slap in
particular, the head arms are made stronger.
Structural support and some cushioning for the disk-head assembly is also provided to help
reduce the transmission of shock energy from the outside of the drive to the platters and
heads, where damage could occur.
|
Anatomy of a head crash. Shock applied to the drive
causes the heads to lift
off the surface of the platters, then snap back causing damage. Newer drives
using shock protection (which Quantum calls SPS) stiffen the head arms to greatly
reduce the chances of head slap, and reduce the damage caused if it occurs.
(Note that the red rectangles are actually the sliders, not the heads...) |
Image © Quantum
Corporation
Image used with permission. |
Enhanced shock protection is certainly a useful enhancement for drives, and it has been
adopted by pretty much every manufacturer in one form or another. If you think about it,
this is really a general way of improving the quality of a drive as opposed to a discrete
"feature", and all drive makers strive to improve the quality of their units,
even if they do it in different ways. Some manufacturers do make more of a "big
deal" about this than others.
And by the way, it should go without saying that no amount of shock protection is
license to treat your hard drives with anything but the utmost of care!
Next: Fly Height Detection
