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Read articleA hard drive in a computer is an internal or external device that stores data such as operating systems, applications and user files. You may also have come across the term HDD. HDD is a common abbreviation that stands for Hard Disk Drive. HDDs are non-volatile storage devices, meaning they retain stored data even when power isn't being supplied.
An HDD includes two main elements: a spinning platter and an actuator arm.
The actuator arm and platter follow the same basic principles of a vinyl record, but in a far more advanced way.
A vinyl record contains only a handful of tracks on its surface, while a modern hard disk may contain 500,000 tracks on each side. Hard disks can also spin up to 15,000 rpm, while records only spin up to 78 rpm. Finally, the read head on the actuator arm acts like the needle on a vinyl record player, following the tracks on the disk. Unlike a record player needle though, the read head doesn’t make contact with the tracks, but instead hovers over the surface of the disk at extremely small distances, less than 10 nanometers. In comparison, a red blood cell is about 7,000 nanometers thick, and a human hair can be 100,000 nanometers thick.
The tracks on an HDD are divided evenly into sectors, and each sector can store a fixed amount of data. As data is written to the hard drive, it’s laid out into these sectors. When a hard drive has been wiped clean or is new, this information can be laid out sequentially, which means it’s very efficient for the computer to read the data again in the future since it’s all in one place.
Over time, as data is deleted or moved, the information is stored in fragments instead of sequentially, which means the actuator arm has to move around the disk surface more often as it hunts for information. This can lead to slower performance, but it’s possible to defrag a hard drive, and reorganize how the data is stored to make it more efficient again.
Instead of an HDD, newer computers are usually fitted with an SSD (solid state drive). SSDs don’t need to be defragged, as the location of data doesn’t affect their retrieval times.
Because the platter and the actuator arm are delicate physical mechanisms, 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.
Underneath the platter, you will also find circuitry and chips that control the components, and memory chips which provide a buffer to assist in reading or writing data to the drive.
Hard drives can be used both inside and outside computers. Internal hard drives are installed inside the computer's case and are directly connected to the motherboard and power supply. External hard drives are housed in their own enclosure and connect to a computer via USB, Thunderbolt or other interfaces. Internal drives are typically used for primary storage, while external drives are often used for additional storage, backups or transferring data between devices.
As your HDD ages, you may start to experience HDD lagging, with slow startups and longer load times.
You can help prevent these slowdowns by occasionally doing a little maintenance work. Follow these steps to immediately improve performance.
Defragging your HDD reorganizes the data to store it sequentially, which leads to faster read times.
Programs and apps can store temporary data that’s unnecessary and can take up a lot of storage space on your drive. To delete this data and free up space on your HDD, follow these steps. Depending on what Windows version you’re using, these steps may be slightly different.
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, videos and games over to an external storage device until you need them. Follow these steps to remove apps and programs. Steps may differ slightly depending on the Windows version you’re using.
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 faster load times. Again, these steps may differ depending on the Windows version you're using. Here’s how to do it on Windows 10 and Windows 11.
The quickest way to improve performance is to upgrade to an SSD (solid state drive), which we'll talk about in the next section.
You now have a good idea of how HDDs work, but there's also a new generation of computer storage available – SSDs.
SSDs are storage drives that fulfill the same purpose as an HDD, only using a more advanced technology.
The benefits of an SSD include:
Upgrading to an SSD helps 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. SATA drives are slower than NVMe drives but are more compatible with older machines. The Crucial® Upgrade Selector or System Scanner can help you find the right storage drive for your computer.
If you’d like to learn more about the differences between SSDs and HDDs, check out our article comparing SSDs and HDDs.
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.
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How much RAM do you need? 4GB, 8GB, 16GB, 32GB - or even 64GB? Find out if you need to increase your computer memory with the experts at Crucial.
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