Hard Disk drive and Solid State Drive

  • Hardware

Brief History of Hard disk drive and Solid state drive

In this article, we will learn about Hard disk drive and Solid-state drive we will first learn the history of both. HDD technology has been developed in the late 1950s but the size of HDD was two large to store small data. It took approximately the size of two commercial refrigerators to store a small amount of data.

In the late 1980’s the size of standardized to 5.25 inches. But in this data capacity was not too much as compared to nowadays hard disks. With the invention of new technology, the size and form factor of hard disk changed to 3.5 and 2.5 inches.

3.5 inches HDD is commonly used in desktops and 2.5 inches HDD is normally used in laptops. For the last many years these sizes are standards of the industry.  Hard disk interface has also changed throughout these years, the old interface was PATA (parallel ATA) or also known as IDE. Nowadays HDDs have an interface is known as SATA (serial ATA).

Solid-state drives (SSD) is new innovation in HDD technology. The main breakthrough in the Hard disk is the method of data storage, speed, and weight with the rising of SSD technology. After 2000 laptops started using SSD as main storage.

We will discuss how Hard disk drive and Solid-state drive are different and shall know the advantages and disadvantages of both. So we can choose proper Storage while selecting a computer desktop or laptop.

Hard Disk drives-HDD

The hard disk drive is a storage device that stores data on magnetically sensitive disks or platters, an actuator arm with a read/write head fixed at the one end of the arm and the other end fixed to the motor .the platters spin due to the motor and actuator arm moves on the platter by which data is read or written. There is also an I/O controller and firmware that guides the hardware for hard disk functioning.

Each platter or disk divided into circles called tracks. Tracks are further divided into sectors. Track and sector number arranged address that can be used to find data on the spinning disk. Hard disks speed is determined by the speed of disks or platters rotate, the hard disks have a normal speed of 5200 RPM to 7200 RPM. When we want to read or write any data from HDD the program of  I/O controller chip activates the actuator arm and is set to the sector or location where the data is located and the data is read by the head with help of charge coding and sent to the user. The time is taken to find the correct track and sector is known as Latency.

Solid State Drives-SSD

SSD is a breakthrough in Hard disk technology. An SSD functions the same as a hard drive, but instead of spinning platters data is stored on interconnected flash memory chips. The data remains in chips even when power flowing in it is turned off. We can think of SSD as a large USB thumb drive but the working of the two is different. It is flash memory which uses a NAND gate the floating gate records a charge or absence of charge to store data. The gates are organized in a pattern or grid and further into block and page. SSD has the main controller chip which is most important and keeps the track of located data. When data is requested from SSD the controller chip reads it from the addresses stored and sends it to the computer.

  In SSD when data is updated it refreshes all the block data. The data written on the existing old block is copied on different blocks and the changed data is rewritten. When a drive is idle all old blocks are erased so blocks get freed to be written again this is called the garbage collection process.

A process called wear leveling also goes on in SSD where the program confirms each block in SSD gets an equal amount of reading and writing processes so it can protect wear and tear of SSD.

We have just seen what HDD and SSD are and what their structure is. Now let’s see what the benefits and disadvantages of both drives in terms of the following mentioned topics.


As discussed the HDD has platters and arm heads that move on the platters for data reading. But in SSD there is no mechanical movement while reading data. The speed of the Hard disk depends on the speed of the motor or RPM but SSD directly read data from blocks so the SSD is faster than the hard disk


            When we purchase any hard disk we always look at which one will be cheaper for purchasing. When the price is compared SSD is much more expensive than the HDD. The small capacity of SSD comes in the rate of big data capacity of the hard disk.

3. DATA CAPACITY.         

Nowadays a laptop normally has a 1 TB Hard disk installed in it. If we compare and want to purchase a 1TB SSD instead of HDD the cost will go much higher cost. SSD of large data capacity is much more expensive than the HDD so if you need to store large data at a cheaper cost hard disk is preferable.


Due to the moving mechanical parts in HDD, it has limitations of size. Normally the desktop has a 3.5” HDD and the laptop has a 2.5” HDD. SSD does not have any size limitations so it is decreasing in size. But SSD normal size of 2.5” to fit in the bay standardized size of laptop or any devices. When SSD is fitted on motherboard slots their size started decreasing. M.2 HDD comes in smaller sizes such as 42mm, 60mm, 80mm, and 120mm.


AS SSD does not have moving parts in it such as motor or platters it does not produce any noise as HDD. The same case is with vibrations very small HDD also produces some vibrations but SSD does not produce any vibrations as it does not have any mechanical part. 


SSD uses less power which results in an increase in the battery life of the device in which it is used. Whereas HDD utilizes more power than SSD.

As seen from the above comparison we see that SSD has better Speed, weight, and power consumption. Whereas HDD has good storage capacity and is less expensive than SSD. Nowadays laptops are generally sold with two Storage devices SSD for fast boot and HDD for large storage requirements.

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