How does a hard drive store so much stuff?

When it comes to computers, the physics and math involved makes them almost impossible for the average person to truly understand. You can look at a small box full of moving parts, about the size of a deck of cards or older cell phone, and this thing can store 2,000,000,000,000 ones and zeroes. It can pull any of them off with astounding speed and can do so again and again for years. I don’t know about you but I think that’s pretty freaking amazing when you really sit down and think about it.

Looking back

I’ve been lucky enough to watch the history of hard disk drives evolve over the last 35 or so years, thanks to my close association with several different computer companies. It used to be a lot easier to understand. Believe it or not, there was a time when a hard drive was huge… 18″ wide and about a foot tall. That was just the disk set… the machine to read it was the size of a washing machine. Back then it was a lot easier to understand what was going on, because you could see the disk heads moving from place to place, and you could see that there were multiple platters spinning around. It seemed pretty amazing, but completely understandable, that a magnet could position itself in just the right place to find the information you wanted to store.

In the 1980s, hard disks went mainstream, or at least a little more mainstream. They went from being these big monstrosities to boxes about the size of a small shoebox. In order to get that level of miniaturization, they also got sealed up in airtight containers. No more watching everything move and spin, but the basic idea was the same. There was a stack of magnetic platters and a bunch of heads that all coordinated together to get your data.

Then… they got smaller.

And smaller. And smaller. It’s not impossible to find hard drives 2″ wide, although 2.5″ is the standard. And they’re so thin now, there’s no way that there are multiple platters in there. At the same time, the capacity of those hard drives has literally increased by a factor of a million. In the 1980s a 1 megabyte drive was pretty special and today, a 1 gigabyte one is routine. Yet it still works much as it ever did.

How did they do it?

There are several tricks that drive makers use to get a ton of information onto one platter. First, by using extremely small magnetic particles, it’s much easier to be extremely precise. The way hard drives store information is by moving single magnetic particles from one position to another. The smaller the particle, the more of them you can pack in a specific space. Another nice side effect is that smaller particles need less energy to move, so the drive can take up less power.

Another method drive makers use is to literally turn the particles sideways, in other words stand them up instead of laying them down. This makes them much easier to pack in a very dense pattern, and that means less space taken up. That’s something drive makers have been doing for several years.

Could there be an end in sight?

At some point you run into the limitations of magnetic storage. The smaller you make the particles, the more densely you pack them, the more the process is prone to errors. It’s likely that we’re coming to a point with hard drives where they can’t really get much smaller or hold much more than about 6 terabytes (which is a massive, massive amount of information.) There may be another breakthrough, but we really have reached the point where the average person has all the storage he needs and only large installations need those supermassive drives.

It’s also easier to build solid state storage in those huge capacities because the technology to pack billions of transistors onto a chip already exists. Flash memory is a little more complex than computer chips since you have to be able to change the information, but the manufacturing process is pretty similar. Unfortunately, it’s still much more expensive to make flash memory or any sort of solid state drive since the technology is newer. The factories that make hard drives are well established and building traditional hard drives doesn’t require paying for those factories.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.