Hard Disk Drive (HDD)

What is Hard Disk Drive (HDD)?

A Hard Disk Drive (HDD) is a non-volatile data storage device that is used to store and retrieve digital information using rapidly rotating disks coated with magnetic material. It is the primary storage device in most computers and laptops.

The hard drive is composed of one or more platters or disks that are coated with magnetic material. A read-write head is positioned above each platter and is used to read or write data to the disk.

Understanding Hard Disk Drive (HDD) Storage

Understanding Hard Disk Drive

An HDD or a Hard Disk Drive refers to a data storage solution introduced by IBM in 1956. This device is usually located inside the computer and the data is stored magnetically in a disk that spins inside.

The multiple heads or transducers on the arm reads and writes data.

It is a non-volatile electro-mechanical data storage device that is used as a primary or secondary storage and is located on a drive bay connected to the motherboard through an ATA, SATA, PATA or SCSI connector.

These are also used in the data centers being capable to store all sorts of files including software programs and operating systems.

The data is stored on the spinning magnetic disc and is read or written with the help of the read and write head placed on the actuator arm.

There are several disk platters made from glass, aluminum or ceramic around a spindle located in a sealed chamber.

There are two motors in it as well where one spins the platter and the other moves the read and write head.

The Hard Disk Drives come in different capacities and some of the most common ranges are:

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Few HDDs also come with larger space up to 20 TB but usually the HDDs do not offer the space as advertised because some of it is consumed by the file system configurations, operating system, and data redundancy procedures.

The general form factors available for these drives in enterprise systems are the 2.5-inch Small Form Factor and 3.5-inch Large Form Factor, which actually represent the diameter of the platter inside the enclosure.

Importance of HDD Storage

The hard disks were the primary forms of storage earlier and are still so for many computer users since they are non-volatile, meaning that the data remains in them even when the computer is shut off.

Thus, your data once you store it is permanent as long as you don’t delete it or there is some problem in the drive.

Hard drives can be used to store all sorts of data including system files, various software data, games, files, movies, videos, etc and pretty much every sort of digital information.

How Does HDD Work?

Every hard drive functions in the same way and has a similar set of components, both moving and non-moving ones.

These include the set of discs where the data is stored, an electromagnet, the head that works to read, or write anything on the disk, a dc motor, etc.

Now, these discs are placed one over the other, much like a stack. They have a thin layer of magnetic metal grains over them.

A certain number of these grains together form very small patterns and each of these patterns is called a bit, the smallest unit of data. 1024 of these bits make a byte, 1024 bytes make a kilobyte (Kb), and so on.

So these bits are stored in the form of binary code (0s and 1s) since the computer doesn’t understand language as we do.

A combination of these 0s and 1s forms each letter of the English Alphabet.

Each of the magnetic grain in a pattern has either of two directions, thus indicating a 0 or 1.

The data is recorded by transforming the collection of bits into an electric current fed through the electromagnetic.

The metal grains’ direction of magnetization is thus changed by the field formed as a result.

The transducer recognizes whether a bit is a 1 or a 0. The head then takes all those bits and transforms them into a readable form.

This, in turn, shows up on your display as a word or an image, or whatever else as the case may be.

Yes, although it seems like it, the metal head never actually touches the surface of the discs.

It hovers above, and a space of about 5nm is maintained between the head and the disc’s surface.

The Pros of HDD

The rate at which data is accessed in these drives might be relatively slow, but they have many advantages over SSDs. Let’s see what those are:

1. Large Capacity

The hard drives usually have a large capacity to store data.

Thus, while a 240 GB hard drive might yet be found, you can easily buy a 2 or 4 TB hard drive at a pocket-friendly price.

This brings us to the next advantage.

2. Cheap

Even the high capacity hard drives are relatively cheaper when compared to SSDs.

The average PC already comes with a 500 GB drive at least, and even if it doesn’t you can buy both internal and external ones at a nominal price.

A 2 TB hard drive, for instance, is available at about $60. Yes, they are that cheap.

3. Long-lasting

Hard drives are the very long-lasting modes of storage.

A hard drive has thousands of reading/write cycles and therefore can last up to 5 years or even more.

4. Can be connected to even when the PC is dead

Suppose due to some reason your PC breaks down. Does this mean you will lose your data? Not at all.

Unless specifically the hard drive has been damaged, you can easily connect the hard drive to another computer using a connector and still find all of your data intact.

Not only that, but there are also yet other methods of collecting data from such a hard drive using BIOS or data recovering software.

The Cons of HDD

5. Not very Durable

Hard drives are not the sturdiest modes of data storage today. They cannot usually withstand a fall or a shock and still function.

This is not much of a problem for desktops, but for laptops, the risks of losing your data are great as you will take it out with you while traveling or might be working outdoors.

6. Slower than SSDs

Both the reading and writing speeds of a hard drive are less when compared to an SSD.

While a hard drive’s speed is measured in RPMs (rotation per minute), SSDs have no such limitations and thus systems with an SSD drive are much faster.

7. Make noise while operating

If you use a hard disk, you might have noticed a slight noise coming from your computer when you are working on it.

This noise is from the hard drive, which is created as it rotates. While this is not extremely uncomfortable, many prefer to work with quieter SSDs.

8. Need more Power

A hard drive requires more power to function than an SSD.

The constant rotation of the disk consumes more power which might not seem too much at first, but in long term usage, you might have to spend a lot.

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Rather, it is better to switch to an SSD initially.

9. Bulky Size

Large capacity HDDs often are a bit too big. This makes it a problem to carry or use them in smaller notebooks and laptops.

This is why many laptops use SSDs so that their lightweight and compact size can be maintained.

Questions & Answers:

Is HDD Good for Storage?

Yes, the HDDs are quite good as a storage solution because it is a proven technology and are quite durable. They offer large storage space and are pretty inexpensive.

Can a HDD be Repaired?

Yes, it is possible to repair a hard drive. However, it is recommended not to use an HDD again after repair because there is no guarantee of it not failing again in the future.

Instead, it is better to recover the contents from it immediately after repair and discard it.

How Does a HDD Store Data?

The Hard Disk Drives usually store data in the form of binary codes using 0s and 1s. The data and information is recorded on the magnetic layer of the disk. The electric current passing over the disk creates an electromagnetic field which transforms the bits while recording.

The disk rotating at high speed creates a layer of air over the surface where the read and write head ‘floats’ to read or write information.

Is It Normal for a HDD to Make Noises?

Yes, it is quite normal for an HDD to make noise, as long as these are mild and familiar. The normal noises include a whirring sound, a single hard clicking sound of the head being parked, and even a fan noise and humming of the power supply of the external HDDs.

The abnormal sounds that indicate a hard drive failure are repeated clunking, scratching or grinding sound that may cause a small amount of vibration.


Hard Disk Drive (HDD) is a popular and reliable storage device that has been used in computers and laptops for many years.

It uses rapidly rotating disks coated with magnetic material to store and retrieve digital information.

While HDDs have a large storage capacity and a relatively low cost per gigabyte, they are not as fast as Solid State Drives (SSDs) and are prone to mechanical failure over time.

Nevertheless, HDDs remain a popular choice for many users who require large storage capacities at an affordable price.