Fun & Facts   Tech
By Lifestyle Team | 12 July 2021

How Does a Hard Drive Work?

hard drive

It’s easy to take certain technologies for granted. For instance, take computers. Computers – and related digital devices like smartphones and tablets – allow us to interact with and store tremendous amount of information. Right now, your smartphone can hold hundreds of times more data than cutting edge computers from the 1990s.

The technology that allows for such prodigious capacity is the hard drive. While it’s your computer’s processor that does all the calculation to make applications run, the hard drive allows your computer to ‘remember’. All that data, those songs, pictures, videos and more, are stored on the hard drive. But how does a hard drive work?

The Power of Magnetism

The concept of the magnetic hard drive has been around for over a half century. While we’ve made incredible improvements in the amount of data hard drives can store, the core concept remains the same.

In order to understand how a hard drive works, it’s necessary to grasp one of the fundamental principles of magnetism. The good news is that this concept is easy to understand. In fact, you’ve probably seen and experienced it in the past.

Certain materials can be magnetized and demagnetized. An example you might have observed in the past is playing with a magnet and any metal object. If you rub the magnet onto that metal object, suddenly that object will become magnetic too. It will have the same properties as any other magnet. A metal object that was previously magnetized can also be de-magnetized in similar fashion.

Now, let’s apply that idea to trying to communicate information. The simplest form of information is ‘yes or no’. In other words, the tiniest bit of info we can communicate is the answer to a yes or no, true or false type question.

We could use the metal object from the previous example to convey a yes or no answer. You ask me if it’s raining today. If I make the metal object magnetic, the answer is yes. If I don’t make it magnetic, the answer is no.

Obviously, this is a miniscule piece of information compared to what you need to render a full-resolution photograph or a feature-length film. But if you take enough of those yes/nos and sequence them together, that’s what you’ll end up with.

And this is the answer to how does a hard drive work – A massive collection of magnetic areas which can be either magnetized or de-magnetized to store information. These magnetic areas are incredibly small and densely packed, allowing us to fit trillions of them within a hard drive no larger than the size of a pack of playing cards.

The Parts of a Hard Drive

A hard drive is relatively simple when it comes to the parts it’s made of. Of course, there’s an incredible amount of sophistication and intricate detail work that goes into creating them. But at a high level, they’re easy to understand.

At its most basic level, a hard drive consists of a platter or series of platters on which the magnetic data is written, and a read-write arm that reads data off the platter or writes it by magnetizing or demagnetizing areas on the platter. Every other part of the hard drive supports one or both of those pieces.

A simple hard drive will consist of a single platter, often times made of ceramics or aluminum. The platter will be coated with a thin metal layer, and that layer makes up the areas that are magnetized or demagnetized to hold data. More complex or larger hard drives will have multiple platters.

Hard drive platter spin at incredibly high speeds, which allows the read/write arm to access all the parts of the platter to access or create new information. The data then flows both ways through circuits to the computer’s processor to execute applications and commands.

The big challenge with writing data to a hard drive is finding it later. After all, there are trillions of little areas on a given platter. A strong organizational pattern is needed.

Hard drives are organized in a series of circular paths running concentrically around the platter. These paths are known as Tracks. Each Track is then broken further up into Sectors.

The hard drive will use some of its space to keep track of all of the Tracks and Sectors. It will know where certain things are written, as well as what Sectors haven’t been used yet. When the time comes to write new data, the hard drive can write into unused Sectors with no risk of overwriting anything that should be saved.

Hard drives are magnetic because magnetism doesn’t rely on electricity to retain its information. You can shut off your computer indefinitely, and all the tiny magnetic areas will remain magnetized and demagnetized as they originally were.