At the moment, high-capacity flash memory devices are still considerably
more expensive than a mini hard drive of equivalent size. But over time, that
differential is expected to become less and less, and at some point a minia-
ture flash memory card may cost the same as a hard drive, and that may
mark the end of the road for mechanical disks in portable devices including
laptops, digital cameras, and video cameras.Hunkering down for a mobile life .....................................................
The good news about a laptop is that it can move from place to place, allowing
users to bring work home from the office or on an airplane or commuter train.
They can be used on a hotel table, atop a bar, or on a lanai at the beach.The bad news is that moving a laptop exposes it to the possibility of being
dropped, falling off a table or bar, or getting splashed or exposed to sand at
the seashore.Protection for water and dirt is accomplished by proper design of the laptop
case. Guarding against damage from the shock of a fall begins with passive
design elements that cushion the hard drive against damage.More advanced safeguards include designs like IBM’s Active Protection System
for some of its ThinkPad laptops. Just as its name suggests, machines with
IBM’s technology include a motion sensor that continuously monitors the
laptop’s movement. Like the sensor in an automobile’s airbag, it watches for
sudden changes in motion that would include acceleration as a laptop tumbles
off a desk or deceleration as it hits the floor. It reacts within 500 milliseconds
(that’s half a second to non-techies) to park the read/write heads of the drive in
a place where they won’t crash into the platters; then it stops the drive’s spin.Going Under the Covers of a Hard Drive...................................................
A modern hard drive, no matter how large or small, is basically a sealed box
with a motor that spins one or more metal or synthetic platters (usually alu-
minum or a specialized ceramic) coated with an oxide that can record digital
0s or 1s. High-tech oxides can be made with compounds of iron, chromium,
magnesium, or other substances. The platter is usually coated on both sides,
meaning that each has two data surfaces. Also in the box is one or more
read/write heads that move in toward the central spindle or retreat to the
outer tracks as needed.Chapter 7: Easing In to Hard Disks 117