There’s nothing like having to replace something before it’s time. When a car, for example, starts breaking down four years after purchase, the owner unexpectedly has to pull together the financing for another vehicle and go through the painful lease or purchase process. Or a television goes out right in the middle of your favorite program when you fully expected it to last at least another two years. It seems nothing lasts as long as it used to—and it can be an expensive surprise.
This can be also true of computers, and in business it can be as expensive as or even more expensive than some car or a television. A company budgets its funds for a quarter or for a year, and having an unexpected hardware failure necessitating a replacement or upgrade turns that budget on its ear. It becomes imperative for an IT department to maintain that hardware and get as much life out of it as possible—and when it comes to hard drives, file fragmentation can rob a good portion of that life.
A hard drive is the only computer component that has mechanical, moving parts that can break down. Every time a file is requested, a read/write head must move across the disk platters and retrieve that file, and file fragmentation adds additional movements for every fragment. Because the free space on a drive is also fragmented, the same holds true for writing a file: the read/write head will have to keep moving until it has written all the fragments of a file in the free spaces available.