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Types of Computer Hard Disk Drives Explained

Patrick, a computer technician, is a dedicated writer who wishes to make the world better by informing individuals who seek more knowledge.

What Are the Main Types of Computer Hard Disk Drives?

Computers rely on hard disk drives (HDDs) to store data permanently. They are storage devices used to save and retrieve digital information that will be required for future reference.

Hard drives are non-volatile, meaning that they retain data even when they do not have power. The information stored remains safe and intact unless the hard drive is destroyed or interfered with.

The information is stored or retrieved in a random-access manner as opposed to sequential access. This implies that blocks of data can be accessed at any time they are required without going through other data blocks.

Currently, we can group hard drives into five types:

  • Parallel Advanced Technology Attachment (PATA)
  • Serial ATA (SATA)
  • Small Computer System Interface (SCSI)
  • Solid State Drives (SSD)
  • NVM Express

IBM 350 RAMAC, Capacity 5MB

The IBM 350 Disk File was developed under the code-name RAMAC by an IBM San Jose team led by Reynold Johnson

The IBM 350 Disk File was developed under the code-name RAMAC by an IBM San Jose team led by Reynold Johnson

Hard Disk Drives Have Stood the Test of Time

Hard disk drives were introduced in 1956 by IBM. At the time, they were being used with general-purpose mainframes and minicomputers.

Like other electronic devices, these have witnessed numerous technological advancements over the years. This is in terms of capacity, size, shape, internal structure, performance, interface, and modes of storing data.

These numerous changes have made HDDs stand the test of time. Not like other devices that became obsolete the moment they were introduced in the market. A floppy disk is a good example.

Hard Drive Types at a Glance

Currently, we can group hard drives into four types:

  • Parallel Advanced Technology Attachment (PATA)
  • Serial ATA (SATA)
  • Small Computer System Interface (SCSI)
  • Solid State Drives (SSD)
  • NVM Express

Parallel Advanced Technology Attachment

These were the first types of hard disk drives to be developed. They made use of the Parallel ATA interface standard to connect to computers.

These types of drives are the ones we refer to as Integrated Drive Electronics (IDE) and Enhanced Integrated Drive Electronics (EIDE) drives.

These PATA drives were introduced by Western Digital and Compaq back in 1986. They provided a common drive interface technology for connecting hard drives and other devices to computers.

Data transfer rate can go up to 133MB/s and a maximum of 2 devices can be connected to a drive channel. Most of the motherboards have a provision of two channels, thus a total of 4 EIDE devices can be connected internally.

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They make use of a 40 or 80 wire ribbon cable transferring multiple bits of data simultaneously in parallel. These drives store data by the use of magnetism.

The internal structure is made of mechanical moving parts. They have been superseded by serial ATA.

An EIDE Hard Disk Drive

A hard disk drive (PATA type)

A hard disk drive (PATA type)

Serial ATA Storage Drives

These hard drives have replaced the PATA drives in desktop and laptop computers. The main physical difference between the two is the interface.

SATA was announced in 2000 in order to provide several advantages over the earlier PATA interface. These are reduced cable size and cost (seven conductors instead of 40 or 80), native hot swapping, faster data transfer through higher signalling rates, and more efficient transfer through an (optional) I/O queuing protocol.

Their method of connecting to a computer is the same. Here are some advantages of SATA Hard Disk Drives. Worth noting is that their capacities vary a lot and so does the prices.

When buying a disk drive, you need to know its storage capacity and how much storage you want.

  • SATA drives can transfer data faster than PATA types by using serial signalling technology.
  • SATA cables are thinner and more flexible than PATA cables.
  • They have a 7-pin data connection, with a cable limit of 1 meter.
  • Disks do not share bandwidth because there is only one disk drive allowed per SATA controller chip on the computer motherboard.
  • They consume less power. They only require 250 mV as opposed to 5V for PATA.

Interface of SATA Drive

A SATA Hard Disk Drive Pin Out

A SATA Hard Disk Drive Pin Out

Small Computer System Interface (SCSI)

These are quite similar to IDE hard drives but they make use of the Small Computer System Interface to connect to the computer.

SCSI is a set of standards for physically connecting and transferring data between computers and peripheral devices. These standards define commands, protocols, electrical, optical and logical interfaces.

SCSI drives can be connected internally or externally. Devices that are connected in a SCSI have to be terminated at the end. Here are some of their advantages.

  • They are faster.
  • They are very reliable.
  • Good for 24/7 operations.
  • Have better scalability and flexibility in arrays.
  • Well-adapted for storing and moving large amounts of data.

Solid State Drives

These are the latest in drive technology that we have in the computer industry. They are totally different from the other drives in that they do not consist of moving parts.

They also do not store data using magnetism. Instead, they make use of flash memory technology. They make use of integrated circuits or semiconductor devices to store data permanently, at least until it is erased.

The basis for flash-based SSDs, flash memory, was invented by Fujio Masuoka at Toshiba in 1980 and commercialized by Toshiba in 1987.

The first commercial flash-based SSD was shipped by SanDisk in 1991. It was a 20 MB SSD in a PCMCIA configuration.

Advantages of Solid State Drives

  • Faster data access.
  • Less susceptible to shock.
  • Lower access times and latency.
  • Durability.
  • Less power usage.

A Solid State Drive (SSD)

Solid State Drive (SSD)

Solid State Drive (SSD)

NVMe Drive

Non-Volatile Memory Express (NVMe) is a storage interface introduced in 2013. “Non-Volatile” means data is not lost when the computer reboots or loses power.

The term “Express” refers to the fact that the data travels over the PCI Express (PCIe) interface on your computer’s motherboard.

This gives the attached disk drive a more direct connection with the motherboard. This is because data does not have to go through a Serial Advanced Technology Attachment (SATA) controller.

NVMe drives are thus much faster than SATA drives. PCIe 3.0 which is the current generation of the PCI Express standard has a maximum speed transfer of 985 megabytes per second (Mbps) on each lane.

NVMe drives have been able to utilize 4 PCIe lanes, meaning a theoretical max speed of 3.9 Gbps (3,940 Mbps).

Meanwhile, one of the fastest SATA SSDs, the Samsung 860 Pro, tops out at read and write speeds of about 560MBps.

NVMe drives come in several different form factors. The m.2 stick is the most common of these.

It is 22 mm wide and can be 30, 42, 60, 80 or 100mm long. These sticks are thin enough to lay flat on a motherboard. This makes them perfect for small form factor computers and laptops.

The PCIe-3.0 form factor is similar to a GPU and it plugs into any of the PCIe-3.0 slots on your motherboard. This is okay for full-sized ATX cases and motherboards.

However, it is constraining on small form factor PCs. On the other hand, it is impossible inside a laptop chassis.

NVM Express (NVMe)

Intel SSD 750 series, an SSD that uses NVM Express, in form of a PCI Express 3.0 ×4 expansion card (Front View)

Intel SSD 750 series, an SSD that uses NVM Express, in form of a PCI Express 3.0 ×4 expansion card (Front View)

Intel SSD 750 series, an SSD that uses NVM Express, in form of a PCI Express 3.0 ×4 expansion card (Rear View)

Intel SSD 750 series, an SSD that uses NVM Express, in form of a PCI Express 3.0 ×4 expansion card (Rear View)

How to Identify Which Type of Hard Drive You Have

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: What is the use of a hard disk?

Answer: The hard disk drive of a computer has several uses, all based on the fact that it is a storage device. Thus we can say that it is primarily used to store computer data for immediate use or future reference.

Some of the uses are:

1. To install the operating system (OS) which tells the computer what to do.

2. To install the application programs that you need to use in a computer.

3. Synchronize your data between computers

4. Back-up important project data

5. Carry data easily

6. Extra storage

© 2012 Patrick Kamau


Patrick Kamau (author) from Nairobi, Kenya on May 26, 2020:

Hello Pushpinder Singh Mangat. Thanks for reaching out. My first question is, did you install an operating system on the new hard drive? If you did well there are a number of reasons that can cause your hard drive not to show up.

What it means is that your computer can’t talk to your hard drive. Remember the hard disk drive contains your operating system, all of your apps and programs, and your files. So without it, your computer is just another piece of junk.

A Hard Disk 3F0 error is a common boot error seen on HP models. Generally, hard disk boot errors can be caused by a whole lot of issues.

These are some things you need to check. Correct BIOS boot sequence, hard drive not properly being plugged in, boot sector viruses, or a corrupted hard disk partition.

Pushpinder Singh mangat on May 25, 2020:

Hi can you please help me i have hp pavilion laptop my hard drive was crashed and i replaced it but new hard drive doesn't shows up it says hdd 3Fo please let me know what should i do


Patrick Kamau (author) from Nairobi, Kenya on December 31, 2019:

Ifraz Imanudeen - This is not true at all. This is just some bad information without any basis. An SSD will las many years if well kept. However, if it is not well kept, it may get faulty at any time.

Ifraz Imanudeen on December 23, 2019:

is it true that SSD data life time is only 05 Years after which data is destroyed so still users prefer SATA HDD for Permanent data storage.

Someone comment on this...

Fotang brice on November 16, 2019:

very interesting to the world thanks man keep it up

LIM on October 24, 2019:

nice article

Govardhan Babu on August 07, 2019:

Thank you it's very useful to me

satish on June 30, 2019:


Jime on April 09, 2019:

Thanks Mr. Kamau, your lecture is so precise and broad in knowledge, My question, please any idea on how to improve a windows 7 laptop that tends become very slow whenever I connect it to the internet, I have tried all these tips of google of eliminating the bloats, clearing the cache, antiviruses, I can't be helped, thanks.

Odotukpono Abraham on March 10, 2019:

Hi there, this is really educative... I am computer engineering students.. I really need help on this computer stuffs

Emmanuel Nyarko Boateng on February 18, 2019:

very interesting to the world thanks man keep it up

yung payn on February 06, 2019:

wow i love what is here thanks

sattar on February 03, 2019:


Dear Patrick Kamau.

I Have a question ??

what is different between surveillance hdd and enterprise hdd and desktop hdd??

Edith Macha on October 29, 2018:

I am here to learn more. Please share

Mustafa on October 20, 2018:

very good information , thanks a lot

Patrick Kamau (author) from Nairobi, Kenya on October 10, 2018:

Hello Kiprop. Most of these Acer Mini Laptops come with a 250 or 500 GB hard disk drives. It is possible to upgrade or change the hard disk as long as you replace with the correct type. In this case, it is not possible that the machine has a 10 GB hard disk.

Kiprop on October 09, 2018:

I have a friend who has an acer mini laptop. There's a certain technician who told her that it's 10GB hard disk cannot be replaced with a larger it true?

smita on October 04, 2018:

Latest technology of hard disk drive

Shri tijare(MH india) on August 04, 2018:

What is the best hard disk drive

G on July 13, 2018:

can a Sata be replaced with a solid state in a labtop?

skzed on July 07, 2018:

which type of hard is toshiba dynabook ss s21 using and where can i get it in Nigeria

KRISHNA KUMAR on April 25, 2018:

is that possible to use replace SDD in the place of SCSI

WIN NAING on March 25, 2018:

can you tell me about ram

WIN NAING on March 24, 2018:

can you tell me more about PATA drives and also RAM

Patrick Kamau (author) from Nairobi, Kenya on March 12, 2018:

It is a type of a hard disk, not a part of a hard disk. SSD is a solid-state storage device that uses integrated circuit assemblies as memory to store data persistently. SSD technology primarily uses electronic interfaces compatible with traditional block input/output (I/O) hard disk drives (HDDs), which permit simple replacements in common application

Rupesh on March 12, 2018:

Is SSD a part of hdd ??

miriam on January 19, 2018:


vivek on October 28, 2017:

Also display use full video thanX

chwechwe gathekia on September 27, 2017:

ssd are less susceptible to shock

jai parkash on September 22, 2017:

ssd drives are best for using all people

Matthew on July 07, 2017:

We now also have M.2 SATA.


Much quicker data rate!

Patrick Kamau (author) from Nairobi, Kenya on April 13, 2013:

lucy patrick, thanks for reading and commenting. I am glad you liked it.

lucy patrick on April 13, 2013:

i like your hub. Thank's patkay.

Patrick Kamau (author) from Nairobi, Kenya on December 09, 2012:

Thanks njeri p, for reading and commenting. Glad you liked it.

njeri p on December 07, 2012:

best description patkay. useful

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