What is a hard drive?

The hard drive is your computer's storage. Here's everything you need to know about it

Need some help understanding your hard drive? We can help! This guide discusses what a hard drive does, how they were created, what types of hard drives exist, and what hard drive properties are particularly important.

Whether you are looking for ways to upgrade your hard drive, trying to buy a computer with the right hard drive, or just trying to figure out what everyone is talking about, read on.

The hard drive’s purpose

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In many respects, the hard drive is your computer. It’s where all the data in your computer is stored for the long term — not just the things you save, but all the code required for your operating system, the framework browsers use to connect to the internet, drivers for your accessories, and everything else. When people talk about computer storage, they are talking about the hard drive.

Every hard drive has a certain amount of space. Some of that space is automatically taken up by the things we mentioned—the operating system, and so on (usually around 10 to 20GB). The rest of the space you can fill with the data you download and save, whether it’s a new app or a funny cat picture someone emailed you.

Hard drive space isn’t as important now as it used to be, although it’s still a major indicator of a computer’s quality. That’s because many types of software can be run online from websites, and a lot of today’s data can be stored in the cloud on remote servers that can be accessed without depending on a local hard drive. This has led to the rise of computers like the Chromebook, with little storage space but a focus on streaming and cloud solutions.

Birth of the hard drive

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In the very early days, computers didn’t have hard drives at all, so they needed different ways to store data so that it could be accessed when necessary. Those old timey ways included rolls of magnetic tape inscribed with data, and yes, punch cards that could be slotted in and read by the computer.

The first real hard drive was developed by Reynold B. Johnson at IBM, in 1956. Johnson’s team was working with better ways to store data on things like magnetic tape. They created ways to store information (in the form of bytes) on magnetic disks instead, which could be overwritten with new information as desired. This led to the development of an automated disk that could read itself in a manner similar to a record player — except much larger.

The first commercially available version, RAMAC, had a hard drive that was about the size of a kitchen pantry. Eventually things got smaller, and IBM additionally developed early floppy disks (in the late 1960s) that could store and transfer information from computer to computer. These two parts, the automated magnetic disk and the smaller, transferable “floppy” disk, became the backbone of the early hard drive. For many years, the method of storing data remained the same, while great improvements were made in how the hard drive could store, read, and eventually write data on the disk.

Two types of hard drives

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Sure, hard drives come in a variety of forms. Some are internal, meaning they’re meant to be connected directly to the motherboard. Others are external, meaning they are made to be carried around and connected by USB. Some can be upgraded, some can’t. But most importantly, there are two core ways that hard drives store data: An older way and a newer way. Understanding today’s hard drives requires understanding both these storage methods.

HDD: HDD stands for hard disk drive, the version that IBM invented as a form of magnetic storage. It uses a magnetic disk that can hold information inscribed in very tiny tracks (again, a bit like a record player). This requires moving parts, specifically heads to read and write data to the disk as needed, and propulsion to spin the disk. It’s a simple method, and so HDDs have become very inexpensive to purchase, especially when creating very large storage setups. For this reason, they are popular in certain databanks and server rooms.

SSD: SSD stands for solid-state drive. There are no moving parts here: Instead, these hard drives use semiconductors that store information by changing the electrical state of very tiny capacitors. They are much faster than HDDs, and can storage information more easily without worrying about parts wearing out. However, they are also more expensive. We can thank SSDs for our modern mobile devices, and they are increasingly ubiquitous in laptops and desktops as well.

Important hard drive qualities

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Space: Obviously, storage space is important! Take a look at available specs for computers today, and you’ll see storage options up to 1TB and frequently beyond. SSDs were particularly important for hard drive storage, because they can store data in a much smaller space than HDDs. That’s why we have phones that can hold all our favorite music playlists.

Speed: The speed of a hard drive depends on how fast data can be read or written, as well as the type of connection the hard drive has to the rest of the computer, and how much data it can carry. HDDs were once rated by rpms/revolutions per minute, but SSDs are much faster and don’t need to spin anything.

Physical security: Physical security is usually about durability — whether your hard drive is tucked away inside a computer or an external version you carry around, it needs to be able to resist bumps and jostles, as well as heat and other environmental issues. More advanced hard drives may also have features that help prevent hacking or discourage theft.

Connections: A hard drive may be connected by USB, SATA, eSATA, PCIe, and other connection options. This affects both speed and what the hard drive is compatible with or how easy it is to upgrade. Always watch connections when buying or upgrading!

Formatting: Hard drives may be formatted to work with particular operating systems or for other precise purposes. Typically you can reformat a hard drive to fit your own needs, but it’s a good idea to check how the hard drive has been formatted if you are making a purchase decision.

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