By Delia / Last update January 26, 2022

Choosing the right hard drive is essential for users who need to store data for a long time, and there are generally two mainstream choices, SSD (solid state drive) and HDD (hard disk drive).

For many years, HDDs have been the first choice for storage because they offer a good balance of storage capacity and price, and that balance has been strengthened in recent years. However, SSDs have caught up in recent years, and prices have become quite competitive.


For now, there are advantages and disadvantages between SSDs and HDDs: SSDs are fast to read, but there is a limit to the number of reads, as SSDs need to erase previous data when re-entering data; HDDs do not have a limit to the number of reads, but are slow to read and write, and have requirements for the working environment, as vibration is more damaging to the heads, and the traditional mechanical structure determines that it will make noise when working.

So how exactly do you choose? Let's take a look at the specific differences between the two types of hard drives.

The structures of HDD and SDD

A hard disk drive is composed of platters, heads, spindles and other parts, its operating principle is the platter around the spindle high-speed rotation, while the head along the radius of the platter movement, by positioning the platter in the specified location to read and write data.

Meanwhile, a solid state drive is composed of control chip, cache chip and flash memory chip, the storage unit is the flash memory particles. Its operating principle is to change the magnetic storage to integrated circuit storage, and the circuit storage is to read and write information through the role of scanning and switching of the circuit.

Since the construction of HDD is much more complex than SSD, it has higher requirements for the environment.

hdd vs ssd

Read & write speeds of HDD and SSD

When a HDD needs to read or write data, it will be instructed to do so and then the heads will move to the appropriate position and the platters will rotate to allow the area where the data is to be manipulated to reach the specified location. The time required for these actions is the seek time plus the latency cycle, and these processes take a few milliseconds due to the movement of the device that needs to occur.

A few milliseconds does not sound like a long time, so why do we often feel that hard disk drives are slow, and even slower after a long period of use?

This is due to the read-write mechanism of the operating system: the hard disk is divided into a number of areas as the most basic unit of operation, the unit is called a "sector". When a new data is written, one or several sectors will be selected for data writing, the location of these sectors are next to each other, logically they are continuous.

However, when the originally written data is modified, there is already other data in the location next to the original sectors, and the new data has to be written to other locations, so the file we see in the operating system is not contiguous in terms of actual physical addresses, and the disk has to do more work when the file is read again. In the worst case, the heads and platters are moved and rotated multiple times, and the work time ends up being exponentially longer.


SSDs, on the other hand, have no mechanical structure and use a simpler design that has a bunch of NAND flash particles to store data. And, unlike another popular flash storage technology, namely DRAM, NAND flash particles are more stable, which means that NAND flash memory retains its charge and thus data even in the event of a power failure.

The read and write process of a solid-state drive is accomplished through the transmission of electrical signals under the command of the master control to read and write operations to the flash memory chip (the basic unit of NAND flash memory is shown below). The electrical signals are much faster than the physical mechanical operation, which is the essential reason why SSDs read and write faster.

The durabilities of HDD and SSD

Because the two types of hard drives are constructed differently, they can be damaged in different ways and to different degrees.

There are two types of HDD damage, one is logically bad sectors and the other is physically bad sectors. The logically bad sectors is relatively easy to repair compared to the physical bad sectors, you can download data recovery software to recover the pieces; if the hard disk situation is more complex and cannot be solved by yourself, you can find a professional remote recovery, or manual recovery, which can generally recover most of the data; if the hard disk damage is more serious, like physical bad sectors, then you can only turn to Professional data recovery agencies.

Although HDDs are susceptible to vibration and high temperatures, resulting in hard drive damage, the data on hard disk drives can generally be retrieved or recovered. Also, HDD failures usually have precursors, such as reading lag or abnormal noises. Meanwhile, SSDs are not susceptible to external factors, but they are basically irreparable once problems arise because they store data through memory particles.

Which one should you choose

It actually depends on your purpose of use. If it is to store a lot of data, it may be more cost-effective and stable to buy a hard disk drive. HDDs usually have a larger capacity, and are relatively affordable. In the event of a failure, the data is also easier to recover.

However, if you are looking to improve the speed and efficiency of your system, it’s recommended to use a solid state drive, as SSD can significantly improve the speed of your computer, more so than replacing the memory and CPU. Many people with old computers that have been in use for years have been given a new lease of life after replacing them with SSDs, with boot speeds going from a minute or two to less than 10 seconds.

Of course, if you have enough slots in your computer, using an SSD as a boot drive and an HDD as a storage drive is also a viable option.