As your computer’s primary storage component, Hard Disc Drives (HDD) are extremely important. However, if you don’t know much about them, it’s difficult to understand exactly how they affect crucial factors like transfer speeds and capacity, or what functions they serve outside of simply storing your data.

If this is you, no worries!

Our comprehensive HDD guide covers everything you need to know about hard drives, from their components, how they work, what types of hard drives are out there, and more!

Table of contents:

  1. What Is an HDD?
  2. What Can You Do With an HDD?
  3. What Types of HDDs Are Out There?
  4. Advantages (and Disadvantages) of HDDs

What Is an HDD?

An HDD, in its most general sense, is a storage device that attaches to the motherboard of your laptop or PC. Most computers come equipped with a standard internal HDD, though the exact specs will vary depending on what kind of computer you purchase.

Without delving too deep into the extensive history and development of the venerable HDD, let’s say that they are still being tweaked and stretched to accommodate the ever-increasing data demands of large enterprise systems and everyday users like yourself, so they are very much relevant.

Check out our comprehensive HDD vs. SSD guide to learn more about what distinguishes one type of drive from the other.

For a very simple breakdown of the anatomy of the HDD, we will focus on these three main components:

Hard Disc Drive with Labeled Components

To put it plainly, the actuator arm guides the read/write head as it hovers above the magnetic platters — or hard discs — allowing the head to read (load) or write (save) your data, kind of like the stylus on a vinyl player traces the grooves of a record.

That leads us to our next question:

What exactly is reading and writing data, anyway?

Girl Reading By Computer

Reading and writing is how your hard drive locates your data.

Each platter places information on concentric paths called tracks, which are subdivided into smaller lengths called sectors.

How it works

When your hard drive writes your data, it refers to a part of the drive called the File Allocation Table (FAT) to discern which sectors are vacant or full. Remember the record comparison earlier? The FAT is like the track selection function that guides the needle to the song you want.

When you save information to a vacant sector, the read/write head seeks out that exact location, where it then transmits and stores that data.

Loading previously saved data — or reading it — follows the same process, just in reverse.

What Can You Do With an HDD?

Hard Disc Drive Feature

Reading and writing data is a phenomenal engineering feat that sounds pretty boring to most people. That is, until you realize all the daily applications it makes possible! In general, we use HDDs for:

Data Storage

Any and everything you save is contained in your computer’s hard drive. That includes your:

  • Music library
  • Photo albums 
  • Documents and other miscellanea (PDFs, Ebooks, etc.)
  • Operating System (OS)
  • Applications and Software (iTunes, Skype, Chrome, Firefox, etc.)
  • System Preferences


While this requires two hard drives, external HDDs are commonly used to backup important files. This is a true lifesaver in the event of a hard disc crash!


Similar to a backup, cloning a drive duplicates everything on one drive to another — literally an exact copy.

What Types of HDDs Are Out There?

There are several types of HDDs to choose from:

Internal HDD

Internal Hard Disc Drives

The Internal drive is located inside your computer. Think of it as your primary, permanent drive.

The only time you will need a new internal drive is if you max out your current one, so you will be looking for higher capacities (measured in Gigabytes) and the appropriate form factor (physical size and shape) for your device.

Depending on your computer, the form factor will vary. Laptops are smaller and come with 2.5” drives, whereas desktop PCs are larger and usually come fitted with 3.5” drives.

Is there a difference?

When it comes to performance, the platters within 3.5” drives reach up to 7,500 rotations per minute (RPMs),while 2.5” drives range around 5,400 RPMs. Higher RPMs mean better overall read and write speed performance, but it also demands more power.

Silicon Power A15 External Hard Drive With a Cable

External/Portable Drives

If you’re running out of space on your internal drive, but don’t want to go through the trouble of migrating data from your old drive to your new one, then you should consider purchasing an external drive.

Most external drives today connect to your computer via a Type-A or Type-C USB cable, drawing their power either from a wall socket or the computer itself. The biggest selling point of any external drive, be it a bulkier 3.5” desktop drive or a 2.5” portable drive, is the portability factor.

They are easy to transfer from one location to another and are great for regular backups, file sharing, and freeing up space on your internal drive.

Want to learn more about external drives? Check out what they are and how they can benefit you in our comprehensive external hard drive guide.

H10 WiFi Wireless Hard Drive

Wireless External Drives

Wireless external drives rely on a WiFi connection to connect to your device (including tablets and smartphones) and a battery as a power source.

Because wireless drives emit their own WiFi network, anyone within range who has the network password can access the drive’s data. This makes it extremely easy to take care of your storage needs on the go.

Advantages (and Disadvantages) of HDDs

Finally, there are some advantages and disadvantages you should be aware of when it comes to HDDs:


Capacity – HDDs are known for their spacious capacities. Currently, one of the largest capacity HDDs is the Western Digital HelioSeal, which can store a whopping 14TB.

Although this amount of space is absolutely unnecessary for the everyday user, it’s impressive nonetheless. On a consumer level, standard HDDs usually run anywhere from 500GB to 1TB.

Affordability  – The average price per Gigabyte currently sits around $.049. (Note: Keep in mind that this price varies depending on capacity e.g. 4Tb hard drives actually cost less per gig than 2Tb hard drives).

So, if you were to buy a consumer-grade, 1TB (1,000 Gigabytes) HDD, this means you’d be paying somewhere between $45-49 before taxes, shipping, and handling.

To give you a rough idea of the pricing trend for HDDs, check out our chart below:

HDD Average Price Per Gigabyte

To give you some perspective, a 1TB SSD currently costs around $0.23 per Gigabyte, which comes out to $229 before taxes, shipping, and handling. Clearly, HDDs are the more affordable drive.

Prevalence – HDDs have been around for more than 60 years now, so it stands to reason that they are more prevalent than SSDs. Many desktop computers still come pre-installed with HDDs, and they are more abundant in brick-and-mortar locations or online vendors like Amazon or Newegg as well.

Many users prefer HDDs for their capacity and SSDs for their performance benefits. Check out our SSD guide to learn more about what they are and how they can upgrade your setup.


Speed – Platters need to hit a certain RPM before they reach operational speed, resulting in slower boot and load times.

Power Consumption & Overheating – HDDs demand more power, which can put a lot of strain on your power supply. Standard 3.5” drives draw between 6.5 to 9 Watts (W), and 2.5” drives draw around 0.7 to 3W.

This naturally produces heat, which can cause a system crash, data loss, or even corrupted discs, which prevents data from being retrieved from affected sectors on the platter.

Noise & Vibration – Mechanical moving parts within the drive create vibration and noise, which can be irksome to some.

Bulky Form Factor – Again, due to mechanical moving parts, an HDD requires a bulkier housing to contain its apparatus.

Sensitivity – HDDs are extremely sensitive to magnetism, impact, and outside elements like dust or water. Were you to drop your drive on the ground (one without a protective casing, that is), it would almost absolutely result in a mechanical failure and the loss of your data.

Fragmentation – Fragmentation means that your data is scattered in multiple locations, so it takes longer for the read/write head to locate and read the information you requested. This can be fixed by a process called defragging.  

Do the disadvantages outweigh the advantages?

This question really depends on your needs. Do you demand responsiveness and lightning quick transfer speeds? Then you might want to look for an SSD.

However, if you just need a standard storage device that gets the job done, then an HDD is the way to go despite its shortcomings.

On that note, many users prefer the affordability of HDDs, and the drive’s performance is still competitive with SSDs. It’s also worth mentioning that hard disc technology is still being developed and perfected, so HDDs are years away from being placed on the legacy shelf to collect dust.

What do you think about HDDs? Do you have any burning questions? Let us know in the comments below!


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