How Does A Hard Drive Work?

We use them daily without ever thinking about it. Yet, how does a hard drive work to store your data?

The average $500 laptop offers 256GB of storage. You could see that figure and think, “Wow — imagine all the movies, songs, and images I could save on that baby,” right?

But did you ever think about how your data is stored?

Indeed, the answer could stun you as the hard drive for your system uses magnetism to store data. When compared to a Compact disc, this approach is more efficient. In fact, if you somehow managed to stack the equivalent capacity of Compact discs before you, it would doubtlessly ascend to eye level.

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How Does a Hard Drive Work?

To fully understand a hard drive, you have to physically know how one works. Basically, there are plates, one on top of the other, spaced a couple of millimeters apart. These circles are called platters. Cleaned to a high mirror shine and incredibly smooth, they can hold vast amounts of data.

Then, we have the arm. This writes and reads data onto the circle. It stretches out over the platter and moves over it from focus to edge, reading and writing data to the platter through its tiny heads, which hover directly over the platter. The arm, on average domestic drives, can oscillate around 50 times per second. This figure can ascend into the thousands on many high-spec machines and those used for complex calculations.

To place things into perspective, for hard drives running at 5,400 RPM, the arm travels 62 miles in 60 minutes. Also, the arm is only 10 nanometres away from the platter, and it is at this distance that the arm has to read and write data on the platter.

To perform this task, hard drives use the concepts of magnetism, and to understand how a hard drive works, we really want to return to certain basics.

Magnetism in Hard Drives Explained

Before getting into hard drives, we should understand the concepts that hard drives use to store data.

Put simply, hard drives use ferromagnetism to save all your documents in seconds. Be that as it may, what is ferromagnetism?

Do you remember keeping a set of paper clips close to a magnet overnight only to discover that the paper clips currently behave like magnets? This behavior of certain metals acquiring magnetic properties when placed close to magnets is known as ferromagnetism. This change in metals’ properties is used to store data on your hard drive.

Although the platter on your drive seems to be a mirror beneath the surface, it consists of trillions of grains. These grains have properties similar to the paper clips we discussed earlier and can store magnetic information when they come close to a magnetic field. To store information, these grains can have two different states, and these states are known as magnetic moments.

In addition to this, unlike the paper clips, the size of these grains is tiny, and a square inch of the platter can store hundreds of Gigabits of data. Subsequently, an electromagnet with a tiny head is used to write data to these small grains. This is the way data is composed on these grains using an electromagnet.

Writing Data to the Hard Drive

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Suppose your computer wants to store a record on your hard drive. This data is nothing but a set of 1’s and 0’s, which change the direction in which current flows in the write head. Because of the current change, the electromagnet’s polarity changes — inducing a different magnetic field in the platter below. It is these differences in the magnetic fields on the platter which create the different magnetic moments in the grains.

In this way, to store 1, the grain will have a different magnetic second when compared to 0. These differences in the magnetic properties of grains enable hard drives to store data.

Understanding the Different Methods of Storing Data on a Platter

Humans are generating more data than at any other time; in fact, in excess of 75 zettabytes of data were created, captured, copied, and consumed worldwide in 2022. This staggering number shows that hard drives need to store more data than at any other time in recent memory. To do this, the grains on platters should be made smaller and crammed closer to each other.

Doing this creates problems as smaller grains can lose the magnetic information they have because of environmental factors. Hence, the magnetic moments should be aligned in different orientations to solve this problem.

Here are the different ways in which data can be stored on the platters:

Longitudinal Magnetic Recording: As the name recommends, Longitudinal Magnetic Recording (LMR) longitudinally stores data. What this means is that the magnetic dipoles have the same orientation as the development of the write head — parallel to the plane of the platter. Although efficient, the size of dipoles on hard drives using LMR innovation takes up a ton of space. Because of this, a density of 100 GB per square inch is presented by LMR.
Perpendicular Magnetic Recording: Also known as conventional magnetic recording, Perpendicular Magnetic Recording (PMR) offers more storage when compared to LMR. The reason for this increase is the difference in the orientation of magnetic dipoles. In LMR, data is stored longitudinally, however with PMR innovation, the dipoles are aligned perpendicularly. Subsequently, the dipoles on a PMR drive are perpendicular to the development of the write head. This change in orientation increases the information density as each dipole takes lesser space when compared to dipoles used in LMR innovation. Because of this, a density of 300-400GB per square inch is presented by PMR.
Shingled Magnetic Recording: As explained earlier, data on a hard drive is stored in grains. These data-storing grains are placed in circular tracks on the hard drive. It is on these tracks that the writer’s head moves to store information. Although these tracks are placed close to each other in PMR and LMR advances, they are not made to overlap as it causes issues when reading the data. That said, SMR overlaps the tracks on the hard drive to increase the amount of data that can be stored on a drive. As these overlapping tracks seem to be the shingles on a roof, this innovation was named Shingled Magnetic Recording. Because of the overlapping, SMR increases storage density by 25 percent.
Heat-Assisted Magnetic Recording: Although the shift from LMR to PMR prompted a substantial increase in the amount of data that could be stored on a hard drive, it was still insufficient for companies like Google, Facebook, Microsoft, and Amazon, which store at least 1,200 petabytes of information. Accordingly, to additional increase hard drive information density, Heat Assisted Magnetic Recording (HAMR) came into the image. This innovation heats the platter using lasers so that grains can be placed closer to each other and the information they store isn’t lost because of environmental factors. Because of this improvement, hard drives using HAMR can store over two terabytes of data in a square inch.

In addition to the alignment of the dipoles, how your drive is partitioned will also affect its performance (and indeed, there is an optimum partition method to maximize performance).

Reading Data From Hard Drives

Now that we understand how data is composed on hard drives, we can take a gander at how the hard drive can read the composed data.

The grains on the hard drive are lined up into a set of tracks. It is on these tracks that the information is stored. When you store a document on your computer, the writer’s head writes in a segment of this track, and the hard drive remembers the record’s location.

When you open the record, the computer chip asks the hard drive to do likewise. The hard drive moves the arm to the same track where the data was composed.

It is here that the read head comes into the image. Very much like the write head uses an electromagnet to write data, the read head uses a Giant Magneto-Resistive (GMR) head. However, unlike the write head, which induces magnetic fields, the GMR recognizes changes in magnetic fields on the platter. Because of these properties of the read head, it can read data from the platter.

Are Hard Drives Still Worth Buying?

Solid-state drives have taken the world by storm, offering faster read/write speeds. That said, this speed includes some significant pitfalls, and finding cheap SSDs with high storage capacities is no easy task.

Consequently, assuming you have a huge gaming library that expands over several terabytes, it’s ideal to get a mechanical hard drive that can store all that data without burning a hole in your pocket.

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