How Hard Disk Drives Use Magnetism to Store Information

Of all of the crazy things about our modern world, I’ve always been most amazed by the way that so many gadgets have become normalized to the point that society completely depends on them, yet only a tiny percentage of people have any idea how those gadgets function. For the most part, people don’t even know how their dimmers work, much less how their laptop accesses the internet. Of course, part of how our society works is by having individuals specialize, and then share the benefit of their knowledge (for a price). Just for the sake of being well-rounded then, here’s a little information about how your hard disk drive stores information.

magnetized nailInherent to your hard drive’s ability to store information is the physical concept of magnetism. You’ve probably fooled around with magnets some, and may have even done that experiment in school where you rub a magnet back and forth on an iron nail, effectively magnetizing it.

Magnetism has been harnessed by humans for a long time. A rather simple example is in the common junk yard, where large magnets are used to pick up large piles of scrap metal.

A use that is just as prevalent but less understood involves sending messages. Whether or not something is magnetized can imply information. Because computers store information using binaries, binary code can be matched to magnetized or not-magnetized microscopically small pieces of metal.

In your computer’s hard drive, these “pieces of metal” are actually magnetized areas embedded in the hard drive’s circular plate or “platter.” Each area can be independently magnetized (to store a 1) or demagnetized (to store a 0).

The platters are by far the most crucial aspect of the hard disk drive. They are generally made of glass or aluminum that is then coated with a thin layer of metal that can be magnetized or demagnetized. Smaller hard drives have only one platter, while larger drives could have entire series of platters staked on a central spindle with a small gap in between them. Platters need to rotate extremely quickly (up to 10,000 revolutions per minute) for the read-write heads to access the information stored on them.

hard drive2Once the 0’s and 1’s are stored, an arm mechanism moves a tiny magnet (called a read-write head) back and forth over the platters to either record or store information and act as a link between the hard drive and the rest of your computer.

Regardless of how many platters there are, there will always be two read-write heads for each platter. One is designated for reading the top surface of the platter and the other is designated to read the bottom surface. The read-write heads are mounted on an arm that can move from the center of the drive to the outermost parts. The read-write heads never touch the platter; there is always a layer of fluid or air maintained between them, at least in a functioning drive.

That’s all for now, but here’s a fun fact: magnetism is an excellent power to harness for computer storage because even when the power is shut off the data continues to be stored.

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