SSD: how does it work and how reliable is it?

SSD stands for Solid State Drive. And that already indicates that this type of storage medium is made of chips and contains no mechanical parts. A completely different operating principle than the old hard disk. With many advantages, but also some disadvantages.

The SSD is on the rise. There is a very good chance that if you buy a laptop now – one with Windows or macOS – it will have an SSD as standard. It is not for nothing that the SSD is popular with laptops. Such a portable computer is used on the road, where every now and then a solid bump or even a fall can hardly be avoided. Now hard drives for laptops do have some protection mechanisms on board, for example a fall sensor that quickly switches off the drive and places the head in the park position in case of an emergency. It's not ideal and an unexpected blow can still cause damage. The hard drive is the most sensitive part in a computer. As long as it is not shaken it will last for many years, but a blow at the wrong time can immediately mean the end. That is very different with the SSD. NAND flash memories are used as storage medium. These are just chips, comparable to what you find in, for example, a USB stick or an SD memory card. And you know that if you drop your SD card, it will have no effect on the data on it. In fact, if your camera is in a thousand pieces on the floor, the photos on the SD card can usually still be read.

Lightning fast

An SSD is therefore very robust, a feature that you would like to see in portable equipment. They are also much, much faster than hard drives. A hard disk largely writes and reads its data sequentially. That is why defragmentation is also necessary, because if by removing and adding new data everything is distributed over the disk surface, reading and writing take more and more time: the head has to change position all the time. A mechanical phenomenon that you can do little about, other than defragmenting. An SSD does not work sequentially. The controller on the SSD keeps track of exactly which data has been written where. In terms of speed, it makes no difference whether data is neatly stored in successive memory locations, or randomly distributed over the memory. In fact, the randomly that data is distributed, the better it is for the lifespan of the SSD.


That lifespan was (and partly is) a thing with SSDs. The problem is that the memory cells of a NAND flash can only be written to a relatively limited number of times. After that they give up the ghost and are no longer useful. It is therefore important to describe the memory in a smart way and to have write actions distributed as fairly as possible over the memory cells. That is also something that the controller in the SSD takes care of. You don't have to worry about that, it's an internal process. Make sure that an SSD is preferably not filled to almost the last bit. You then no longer have any memory cells left for the rotation of write actions. Keep breathing room and everything will be fine. In fact, an SSD is no longer really inferior to the hard drive in terms of lifespan. And certainly not in a laptop, where the hard disk often gets problems much sooner due to vibrations, bumps and falls.


We already mentioned the much higher speed. That makes the SSD (of course) also interesting for desktop PCs. You often see there that the operating system and programs are on an SSD and the disk space-consuming data on another, traditional hard disk. SSDs are still more expensive than hard drives in terms of storage space. This is especially the case with larger drives. A 500 GB SSD or even a 1 TB SSD is now very affordable. 3 TB or more becomes a rather expensive joke. However, because the prices of SSDs are steadily falling, you see that they are also used in NAS, previously mainly reserved for traditional hard drives. An SSD can be used in a NAS as a cache, but there are also NASs that are fully equipped with SSDs. Not only does the speed advantage play a role here, but also the fact that SSDs produce no sound. In environments where you would rather not have buzzing disks on your head, a wonderful solution.


The SSD will definitely become the standard for the future when it comes to storage media in computers (and of course also tablets and smartphones, where this is really the only option). In addition, manufacturers will make flash memory increasingly reliable. And even radically different techniques will appear that do not know wear and tear on the memory cells. When the time comes, we may have finally invented the ideal storage medium. That can withstand a heavy blow and is durable for decades. But that's still a dream.

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