For years, hard drives were the only viable large-capacity persistent storage format for our PCs. This was in this way until the appearance of solid state drives, known by its acronym in English SSD. In any case, you may have wondered why we do not talk about SSD hard drives and that is because this is technically incorrect. However, we believe it is important to explain why.
Many people mistakenly call SSDs a hard drive, and although it is a term that colloquially helps to understand that both components have the same task: to store data and programs persistently. However, your solid state drive is not a solid state drive either. So, if you have been using such terminology, erase it from your mind. The reason? Keep reading.
Why is an SSD not a hard drive?
The answer to the question is simple, despite the fact that its functionality is the same, the way it works is not the same and they are two very different devices . It is literally like comparing a horse carriage with a car, both are used to carry people, but they do not work the same.
The hard disk is based on a head on a magnetic disk that rotates . So to find the data there must be two mechanisms. On the one hand, the one that rotates the disk and on the other, the one that moves the needle to move the data. Its name is due to the fact that the surface where the information is found is made with a product that is solid and not flexible. Nowadays it would be correct to call them dry disk drives, since floppy disks or floppy disks are no longer used
An SSD, on the other hand, is based on non-volatile memory chips , so they do not lose information when we turn off the PC. They do not use mechanical parts of any kind. Think of it like RAM, but much slower to access and can hold data for a long time. So the way of accessing the information by the processor is totally different.
The needle weighs
The fact that the disk drive uses a needle to access information means that read speed has a huge mechanical bottleneck. Since it is necessary to move the needle from the inside to the outside of the record and vice versa, and we cannot go faster than its speed. Unlike a hard drive, an SSD relies on electrical impulses and doesn’t have to move anything. Which allows you to solve several requests for information at the same time.
After all, it works like RAM and in the same way that having several memory chips means several parallel accesses at the same time. Imagine the line to the roller coaster in an amusement park. In the case of the hard drive we would have a single queue, but with an SSD or solid drive we have several at the same time and the waiting time for each data request is greatly reduced. This means that the data arrives with less latency when it has to be dumped to RAM.
The other problem is that while the needle is moving on a hard drive it is not transmitting data. In memory chips there is also a synchronization period, but it is tiny in comparison. Moreover, both in SSDs and in a hard drive, things get worse when you jump from one part of the memory to another, however, it is much worse in the first case.
