What is the difference between HDD and SSD

What is the difference between HDD and SSD

To choose the form of storage for our equipment, it is essential to understand the differences between HDD and SSD, which are the two options that we will be able to choose. Technical differences between HDD and SSD, how do they work?

Speed

Accessing data on an HDD has the disadvantage of having to constantly scroll through it. Basically, the disk rotates at a speed that is usually 5400 or 7200 rpm, and meanwhile the head moves over its radius, being able to find and store the necessary information at a fairly high speed. No matter how fast the disk is going, the data can be in very different locations and the head will have to do a lot of work to find the information.

An HDD will never exceed the speed of an SSD, whose access to information is much more direct: the controller simply accesses the necessary memory cell directly. The difference translates into read/write speeds of between 400 and 10,000 MB/s for SSDs (depending on quality and whether it is SATA or NVMe), while for an HDD we can expect between 50 and 250MB/s or even less.

In addition, not only do you have to take into account the differences when reading/writing large files, but also when accessing many small files, which is something that happens when you turn on your computer or open any program. This is measured by latency, which can be 10-15 times higher on an HDD, which is outrageous.

The practical result of all this leads to one of the most obvious differences between HDD and SSD: the boot speed of our computer. Think of a PC full of programs and files that hasn’t been formatted for years: if you have an HDD, it will most likely take minutes and minutes from the moment you turn it on until you can use it. On the other hand, with an SSD it will be a matter of seconds, yes or yes.

In summary, an SSD is much faster and thanks to its low latency it does not choke when encountering a large number of different files, something that an HDD does not.

Noise

Another important point in the differences between HDD and SSD is noise. This part is easy: the 7200 rpm of a mechanical disk is quite noticeable and it can become the noisiest component of our PC, with annoying vibrations.

On the other hand, an SSD having no moving parts does not make noise. Simple as that. This is very noticeable, especially in laptops where the noise and vibrations of an HDD are much more evident.

With these two points, we have already found the great advantages of an SSD over a mechanical drive, but there is still more to talk about.

Storage capacity and price

An HDD can reach much larger storage capacities, while SSDs are still in development in this regard. But be careful, because while HDD research is more stagnant, the panorama with SSDs advances by leaps and bounds every year. SSD capacities now were unthinkable just a few years ago.

Regarding the price, we will explain the current situation. We are not going to talk about hard drives for servers and data centers, where the difference is more evident. So, we conclude that the lower price of HDDs is a historical reality, but in practice the differences are tiny compared to what we gain in speed.

Durability

Is an SSD more durable than an HDD? Since SSDs are so good, we could say yes and that’s it, but the truth is that it is not that easy. This is one of the most difficult differences between HDD and SSD to clarify.

On the one hand, the mechanical nature of an HDD makes it much more vulnerable to two aspects: the environmental conditions in which it is found and any blow, movement or vibration suffered by the disk.

Generally, in a normal operating environment and without heavy shock, an HDD can last a lifetime. This makes them very reliable for NAS or storing very long-term backups. Instead, SSDs have two very clear durability issues.

The NAND memories of an SSD have a data write limit after which they wear out too much and are unreliable. Therefore, all SSDs have a written data limit called TBW (Total bytes written), which varies according to capacity and quality. For example, a 1TB Samsung 980 has 600TBW, which means we can write up to 600TB of data. When they are reached, the SSD goes into read-only mode to safeguard the data.

It is practically impossible for us to reach TBW by making normal use of the SSD, even if we keep it for many years. An HDD does not have this specific limit, but it is exposed to the actuator having a mechanical failure and leaving us stranded.

The data retention of an SSD, a problem? The electrical charge that holds information on an SSD does not last a lifetime. If we disconnect power to the SSD for a very long period, data may be lost.

The difficult thing is to say when the data will be lost. This depends a lot on the ambient temperature at which the SSD is in storage, most likely around 20ºC because we are talking about the SSD completely disconnected.

Conclusion on the differences between HDD and SSD

So, let’s recap on the differences between HDD and SSD in order to give you a recommendation. Which one should I buy for my PC or laptop?

As we have seen, SSDs outperform HDDs in terms of speed, latency and noise, providing an infinitely superior experience for users. In durability it is difficult to establish a winner because both options have advantages and disadvantages.

Until a few years ago, the price was one of the differences between HDD and SSD that put solid state drives more in check. But, with the excellent prices that are being seen now, there is no longer any discussion: it is crazy not to have an SSD in your PC. The performance improvement is extreme, both in numbers and in actual experience.

  • You should never buy a PC or laptop that does not have an SSD. It doesn’t matter how cheap it is. At best, buy it and immediately replace your HDD with an SSD.
  • If the PC has a main SSD and an additional HDD, it doesn’t have to be a bad idea. But, if it’s a laptop, it’s better if it doesn’t have an HDD because of its noise and vibrations.
  • If you have a PC with an HDD and it is old or does not work very well anymore, the first thing is to change to an SSD.