PART I - INTRO & FRAGMENTATION
Many people are under the impression that a computer's performance
deteriorates with age. I'd like to dispel that myth: computers are mostly
solid-state technology that is largely unaffected by age. I'm not saying that
older computers don't run more slowly, but once we correct the notion that the
slow-down is caused by its unalterable age, the problem becomes one that can
usually be remedied without buying a newer computer.
First, let's understand what doesn't cause a
computer to slow down:
- Computer
processors are digital electronic transistor-like switches, sealed in a
hard plastic package; these are solid-state devices that either work or
don't. They may get fried if exposed to a power surge, but otherwise, they
don't slow down.
- Computer memory
is comprised of similar components and works or doesn't work, just the
same.
- A computer
motherboard is nothing more than wire traces on a piece of plastic,
usually with more solid-state devices plugged into it or soldered to it.
Motherboards don't slow down, either.
- Computer power
supplies are exposed to some of the most extreme conditions a computer
experiences. That's why they burn out more frequently than most other
parts, but even they don't cause performance reductions; they either work
or they don't.
So what does cause a computer to slow down with
age?
The biggest culprit is data storage. Imagine trying to look for
something in a file cabinet if it was the only item in the drawer; it would be
pretty easy to find, right? If there were even just a few items in the drawer,
it would still be simple to thumb through them to find the one you wanted. What
if the drawer was completely filled? It might take a little longer, right?
That's what happens on a hard drive when you install an operating system,
applications, and data on it. Every time you download more.mp3 songs, import
more.jpg photos from your camera, or type up new word processing documents,
you're stuffing more things in the file cabinet which is your hard drive.
Unlike the processor or memory, the hard drive is usually not a
solid-state device; it has moving parts. Consequently, the time it takes to
read or write hard drive data is on the order of 1,000 times slower than
solid-state devices like RAM or a USB thumb drive. Couple that with the fact
that you keep adding more and more stuff to it, and you can begin to understand
the problem.
In reality, it's even worse than you imagine. When you save a
document to the hard drive, it gets stored in a specific space on the drive.
The computer tries to allocate hard drive space as efficiently as possible, so
if more stuff gets written to the drive after that, it's stored in the
next-available sequential space. (For the hard-core techies reading this, yes,
I know that this explanation severely oversimplifies the process.)
Unfortunately, that means that when you next edit that initial
document, there isn't any contiguous space on the drive for the new data to be
stored, so it ends up getting stored elsewhere, separated from the first part
of the document. Later, when you try to read this document back into memory, it
takes a little longer than it would for a contiguously-stored document because
the computer must make a jump in the middle of reading it to find the rest of
it. This is known as fragmentation. Another cause of fragmentation is when
files are deleted, as that creates holes the computer tries to fill with
subsequently-saved data, but the holes are almost never the right size for the
new files being saved, so the newly-saved files also get broken up into
noncontiguous pieces.
Don't think your use is the only force causing fragmentation on
your drive, either. Virtual memory, pointers to recent files, various cache
files, and updates/patches use and release hard drive space all the time,
causing fragmentation, even if you never intentionally save another file to
your computer. Fortunately, fragmentation is relatively easy to cure. Microsoft
Windows comes with a tool that does it for us - all we have to do is use this
tool from time to time, and it rearranges the files on the disk to do its best
to store them all contiguously. Lucky for us, a lot of the stuff we store on
our hard drives doesn't change all that frequently. Operating system files,
installed applications, and even our music and photos rarely change in content
or size, so once they get defragmented into less-dynamic areas of the hard
drive, they should be fine.
PART II - DIGITAL HOARDING
After fragmentation, the next issue to discuss about how hard
drives slow down our computers is the increasing volume of data being stored on
them. If you've seen a phonograph turntable, you have a rough notion of how a
hard drive operates, but imagine it spinning much faster. Instead of 33 or 45
revolutions per minute, hard drives operate at 5,400, 7,200, 10,000, or even
15,000 revolutions per minute. For even the slowest hard drive to spin around
to the complete opposite side of the disk may take under 1/100th of a second,
but like a phonograph turntable, rotation isn't the only motion the drive
makes; the head also moves in and out, radially, and that motion is
significantly slower. When a hard drive has little data on it, that data is
generally stored close to the center, so the head only needs to traverse a tiny
fraction of the radius of the disk, but as more and more data get stored, more
of the radius of the disk is used, so the portion of the radius that the head
must travel gets longer, making data reads and writes slower.