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Hard drives are pretty much the same as they were a few years back. The
fundamentals are the same, but many new technologies have allowed more
performance and value to be squeezed from modern hard drives.
A hard drive is a dirt free environment inside an airtight case, which
is critical for avoiding damage to the parts inside. A number of discs,
called platters, spin around on a spindle. There can be from one to
five platters in a single drive, although most drives just have one.
For each platter there is a little arm with a read/write head on the
end. These arms, one per platter, stretch out over the platter sort of
like a record player and magnetically change the arrangement of the
material on the surface. These heads never touch the platter, but float
ever so slightly above them.
All drives have this basic design, but utilize other technologies to
get the most from the drives. Notably there is often very little
difference between competitors when using comparable systems. Drives
with the same specifications, from two different manufacturers, will
not very much in performance.
Drives come in a few different sizes. The standard desktop hard drive
is one inch in height, while models for laptops are 9.5mm or 12.5mm,
with the latter becoming too big for current laptop designs. There are
also proprietary sizes available.
The number of platter depends on the use of the drive. Most drives only
have one platter, which reduces the number of moving parts, namely the
arms and heads, resulting in less chance of drive failure. Multiple
platters allows for greater storage capacity. Laptop drives can have up
to two platters. Desktop drives have 3.5 inch platters, enterprise hard
drives look like 3.5 inch drives, but have 2.5 inch platters inside.
Mobile drives have 2.5 and 1.8 inch platters, while some micro-drives
use 1 or 0.8 inch platters.
Spindle speed, which is how fast the platters spin in the drive, makes
a huge difference to the performance of the drive. Think about it, the
faster it can spin, the faster the information that is being looked for
will pass beneath the read/write heads, it's just quicker. Server and
workstation drives usually spin at 15,000 or 10,000 RPM. The WD Raptor
is the exception for desktop computers, also spinning at 10,000 RPM,
but usually they spin at 7,200 RPM. However the price of a Raptor is
very high and you pay more for its 150 GB model than for a 500 GB drive.
Notebook drives spin at 4,200 RPM, which is slowly being replaced by
5,400 RPM models. Smaller mobile drives operate at 4,200 RPM, while the
micro-drives operate even slower.
The cache that the hard drive uses helps to store data that will be
needed and store data that is used very often so that a physical read
from the platter is not needed. This gives great speed improvements for
frequently accessed data. Drives with a cache will give faster
performance. Up to 16 MB is offered on some drives, but 8 MB has been
found to be the most worthwhile, as 16 MB provides little extra
performance over 8 MB.
The performance difference within a family of hard drives is very
little. The biggest differences are found by moving up to 10,000 RPM,
but with an obvious price penalty. For best value per GB, divide price
by disc size and go from there.
About the Author
Find out all the other things you need to know about getting a hard drive at http://computer-buying-guide.com/hard-drives
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