Difference Between SSD and HDD

In computer systems, different types of memory devices are used to store data permanently. Both SSD and HDD are such storage devices. SSD and HDD are the most commonly used types of secondary memories. HDD is a traditional storage device, while SSD is a modern storage device.

SSD and HDD are quite different from each other. The most fundamental difference between SSD and HDD is that SSD (Solid State Drive) is a storage device that stores data in integrated circuits, whereas HDD (Hard Disc Drive) is a device that stores data magnetically. There are several other differences between SSD and HDD, which we will discuss in this article.

What is HDD?

HDD is a storage device used in computer as secondary memory. It is made up of a series of circular disks (called platters), these platters arranged one over the other almost ½ inches apart around a spindle. The platters or disks of HDD are made up of non-magnetic materials like aluminum alloy and are coated with a layer of 10-20 nm of a magnetic material.

In a hard disc drive, the standard diameter of a disk is 14 inches. These disks rotate at speeds ranging from 4200 rpm (rotations per minute) for personal computers to 15000 rpm for servers. In the HDD, data is stored by magnetizing or demagnetizing the magnetic coating.

To read data from and write data on to the disks, a magnetic reader arm is used. A typical modern HDD has storage capacity in terabytes (TB).

What is SSD?

SSD is a semiconductor-based storage device that uses integrated circuits to store data. There are no moving mechanical parts in a SSD. SSDs are more reliable and long-lasting as compared to conventional HDDs.

SSDs are relatively more robust and resistant to physical shocks, and run silently. SSDs have smaller access time and lower latency as compared to HDDs and other magnetic storage devices.

SSDs are relatively expensive because they are newer technology storage devices, however the price of SSDs has decreased over time. SSDs are very popular secondary storage devices in modern desktop and laptop computers.

Difference between SSD and HDD

The following table highlights the important differences between SSD and HDD −





It stands for Hard Disk Drive.

It stands for Solid State Drive.


It contains moving mechanical parts such as the arm.

It doesn't contain mechanical parts, only electronic parts like ICs.


It has longer R/W time.

It has a shorter R/W time.


It has high latency.

It has low latency.


It supports less number of I/O operations per second.

It supports more number of I/O operations per second.


It uses fragmentation.

It doesn't have fragmentation.


It is heavy in weight.

It is lightweight.


It is larger in size.

It is compact in size in comparison to HDD.


The data transfer in HDD is sequential in nature.

The data transfer is done in a random manner.


It is less reliable since there could be a mechanical failure in it, such as the head crash and susceptibility to strong magnets.

It is reliable, because it does not contain moving parts.


It is cheaper with respect to per unit storage.

It is expensive with respect to per unit storage.


It is an older technology.

It is a relatively new technology.


It produces noise due to mechanical movements.

It doesn't produce any noise.


Both SSD and HDD are used as secondary storage devices in computers. However, they are completely different from each other as described in the above table. The most significant difference is that SSD is a solid state memory device, whereas HDD is a type of magnetic memory.