A hard disk drive (HDD) is an internal or external computer component that stores data, such as the operating system, applications, and user files.

HDDs are “non-volatile” storage devices, meaning they retain stored data even when power isn't being supplied.

How does a hard drive work?

An HDD includes two main elements; a spinning platter and an actuator arm.

  • The platter is a circular magnetic disk containing tracks and sectors that retain data.
  • The actuator arm moves across the platter to read and write data.

The platter spins (hence the name) on a spindle to help speed up the read/write process as the actuator arm moves across it.

The data sectors are spread out randomly (also known as fragmented) across the platter, and below we'll discuss defragmenting a hard drive to boost performance.

What does a hard disk drive look like?

The platter and the actuator arm are delicate physical mechanisms, so a solid case covers them to prevent damage under normal use. The hard drive cover will look like a metal box, and it will be clearly labeled as a hard disk drive or HDD.

Here's what an internal HDD looks like beneath its metal casing. You can see the spinning platter and the actuator arm, and how they work together to read and write the data upon request.

A hard drive

Instead of an HDD, newer computers are usually fitted with an SSD (solid state drive).


What are the advantages and disadvantages of an HDD?

Advantages of an HDD:
Disadvantages of an HDD:
  • HDDs can store a large amount of data (this varies by the drive size)
  • They are relatively cheap compared to other storage solutions
  • HDDs can be slow at retrieving larger files
  • They consume more power
  • The moving parts produce a lot of heat
  • They are less durable, especially in portable devices

If you’d like to learn more, check out our article comparing SSDs and HDDs.

How to improve hard disk performance

As time goes on, you may start to experience HDD lagging, with slow start-ups and longer load times.

You can help prevent this by occasionally doing a little maintenance work, which should improve performance immediately after you follow these steps:

1. Defrag your hard disk drive – this reorganizes the data to store it sequentially for faster read times.

2. Delete temporary files – programs and apps can store temporary data that can take up a lot of storage space on your drive. Depending on what Windows version you’re using, these steps may be slightly different:

  1. In the search box on the taskbar, type disk cleanup, and select "Disk Cleanup."
  2. Select the drive you want to clean up and select OK.
  3. Under "Files to delete," select the file types you want to remove. You can also select a file type to read a description of what it is.
  4. Select OK when you have made your selections.

3. Remove unnecessary data – freeing space is a great way to improve storage performance. This could be deleting old programs and apps you no longer use or moving photos, films and games over to an external storage device until you need them. These are the steps to remove apps and programs, but this may differ depending on the Windows version in use:

  1. In the search box on the taskbar, type programs, and select "Add or remove programs,"
  2. Select the programs you want.
  3. Then select “Remove.”

4. Enable write caching –this step enables the volatile memory (RAM) to collect data in a cache before writing it to the storage device. The cache can process the data faster, resulting in fast load times. Again, these steps may differ depending on the windows that you're using.

  1. Right-click "My Computer," and then click "Properties."
  2. Click the "Hardware tab" and then click "Device Manager."
  3. Expand "Disk Drives."
  4. Right-click the drive where you want to turn disk write caching, then click "Properties."
  5. Click the "Policies" tab.
  6. Click to select or clear the "Enable write caching" on the disk check box as appropriate.
  7. Click OK.

5. Upgrade your storage – the quickest way to improve performance is to upgrade to an SSD (solid state drive), which we'll talk about in the next section.

Other memory storage options

Solid state drives

You now have a good idea of how HDDs work, but there's also a new generation of computer storage available – the SSD.

SSDs are storage drives that fulfil the same purpose as an HDD, only using a more advanced technology.

The benefits of an SSD include:

  • They use less power
  • They produce less heat
  • They don't have moving parts, making them more durable

Upgrading to a solid state drive can help boost the performance of your PC or laptop, but one thing to consider when doing so is compatibility.

SSDs come in different forms, whether that be SATA or NVMe. The Crucial® System Selector or System Scanner can help you find a suitable SSD for your computer.

External storage

If you want to increase your data capacity without replacing your internal hard disk, adding an external storage drive is a quick and easy way to expand your storage capabilities.

FAQs for hard disk drives

  • What does a hard drive do?

    A hard drive is a physical computer component that stores data, including programs, pictures, documents, and your operating system. Nearly all computers come equipped with an internal storage drive, and you can also add external hard drives for more storage space.

  • What does HDD stand for?

    HDD stands for “hard disk drive,” and is a type of hard drive commonly used by older computers for data storage.

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