As usual, first show me the Hard Disk Drive (HDD).

Yes! Most of us could have seen a hard disk drive, because hard disk space will be the first ever need of any PC beginners.

Generally it’s found in the slots below DVD drives. They are similar to DVD drives, but comparatively smaller and sleek. If you have opened the computer while it is ON, you can feel the warmth of HDD (Hard disk drive). Except in bottom, HDD has chrome or steel like finish on all sides and only in bottom, you can see a PCB.

What’s inside a HDD?

There will be some pile of discs placed one over another inside the HDD. They are magnetic discs, unlike DVD (because DVD is an optical disc). More or less the magnetic disk inside HDD and DVD look similar, but their way of operation is entirely different, because DVD stores 1s and 0s through a laser beam projected on it, whereas HDD stores 1s and 0s through magnetization of particular spots in the disc.

What happens to HDD when you shut down your PC improperly?

Have you ever wondered why you can’t switch ON and OFF your PC just like TV?

One of the reasons is HDD. After boot up, the CPU has to access the OS from HDD and store it to RAM, then only it can do the rest. So for this process the HDD should be immensely faster, which is not possible in mechanically rotating discs.

Normally the magnetic discs inside your HDD rotate at some rpm, even when you leave your PC idle. Also the reading head will constantly be touching the magnetic discs. So when you shut down improperly the reading head may damage the spot in the disc at which it is touching, when you shutdown improperly.

If this happens again and again, then several bad sectors will get formed in your hard disk. Finally you may need to change your hard disk or you may need to perform Check disk operation often or some important information may get corrupted. But most of the time if you schedule a boot time disk check, then those files system errors will get corrected automatically.

Why we need a hard disk?

We need hard disk for storing our data, Mp3 songs, documents, videos, films etc.

But how much we need? 100 GB, 500 GB or what?

Basically if you’re just a casual Internet user then you will not need anything more than 320 GB hard disk.

If you’re a gamer then you may need a minimum of 500 GB hard disk, because nowadays, most of the popular computer games consumes around 14 GB disk space.

If you have a digital camera of more than 10 MP or a HD camcorder then you will need a hard disk of minimum 500 – 750 GB, as these digital devices take lot of space for storing digital photos and videos.

Besides these things if you own a Full HD monitor and if you have lot of movies in Blue ray quality, then also you may require a HDD of size more than 500 GB, to store HD or Full HD movies.

Split up of 1 TB

Each 0s and 1s consume a bit.

1 Byte = 8 bits e.g. ‘10101010’

1 Kilobyte or KB = 1024 Bytes

1 MB = 1024 KB

1 GB = 1024 MB

1 TB = 1024 GB

Nowadays we have desktop hard disks up to 4 TB. The actual size of HDD is 2.5″ or 3.5″.

How to measure the speed of HDD?


Moreover the speed of HDD is measured in terms of rpm (revolutions per minute) or maximum data transfer rate. It ranges from 5400 to 7200 or 15000 rpm. If you go for higher rpm HDD, then you will get higher speeds, but the cost will also go high. Generally the speed of HDD (data transfer rate) lies between 50 – 120 MB/s.

But in earlier days we have no other option than HDD to store our files. But now we have SSDs and Hybrid SSDs. We will see about them tomorrow.