How does an SSD work

How does an SSD work?

An SSD (short for Solid State Drive) is a storage medium for computers that is designed to function like a hard drive. In terms of its functionality, the SSD is not based on a magnetic memory, but on semiconductors, such as the electronic memory components used in the main memory.

An SSD usually has connections that are compatible with hard disks and can be used in the same way from a practical point of view. However, it is significantly faster when reading the data.

SSD types

There are several types of SSD, which differ significantly in their functionality: Flash-based SSD, SSD based on SDRAM technology and hybrid hard drives that combine the technology with a conventional hard drive. Flash-based SSDs are by far the most common; SDRAM-SSD are more likely to be found in the professional sector, for example in servers.

Flash-based SSD

Flash-based SSDs are based on the same technology as flash memory cards that are used, for example, in digital cameras or cell phones. They are non-volatile; that is, the information stored in your memory module is not lost if the power supply is interrupted. Each individual bit is stored in the form of an electrical charge on a so-called floating gate transistor. These special transistors contain an electrically insulated electrode, the "floating gate", on which the charge can be permanently stored. If a positive voltage is applied to the floating gate, the charge is stored. In order to discharge it again, a negative voltage must be applied - therefore no information is lost if the power supply is interrupted. The advantage of flash-based SSDs is energy independence and low power consumption, but they are slower than SDRAM-based SSDs and their lifespan is shorter.


SDRAM-based SSD are based on RAM memory modules. They are volatile, so they need a permanent power supply and consume significantly more power than hard drives or flash-based SSDs. Therefore, they are supplied with a backup battery or their own power supply. The advantages of SDRAM-based SSD are the very high speed - around 80 times as fast as with flash memory - and the significantly longer service life.

Hybrid hard drives

Hybrid hard drives usually have a flash memory and also a conventional hard drive. They combine the advantages of both technologies: Compared to the hard disk, the flash memory is faster to read, but slower to write the data and is more expensive. For this reason, only data that is frequently accessed is stored on the flash module.