How Do Solid State Hard Drives Work?

Unlike magnetic hard drives, solid state hard drives have no moving parts and do not rely on magnetic fields to store data. Because they use electrical current, rather than motors and magnets, to store data, they can access data noiselessly and with less power consumption. Solid state drives are also not subject to the same physical damage from impacts or large magnetic forces, making them suitable for mobile computers.

Solid state hard drives use a series of transistors, pieces of silicone and semiconductors to transfer the electrical current. Each piece is microscopic and can be affected by the transfer of a few electrons. Like all data storage, solid state drives use binary, a series of 1s and 0s, to represent data. A 0 is represented by a transistor that cannot accept an electrical current, while a 1 is represented by one that allows the flow of electricity.

A blank drive, or a blank section of the drive, is denoted by all 1s. All transistors in this section will allow the free flow of current. When data is recorded, voltage is applied to one piece of silicone, known as the control gate. This process transfers electrons to another piece, the floating gate. When the floating gate is filled with electrons, current will not pass through it and the drive reads it as a 0.

As you write or delete data from the drive, the information is converted by the program to binary data. This is sent to the drive's writing center, where it is converted to electrical currents and used to realign the transistors. To read data, the read center of the drive sends a current through the portion that holds the data to be read and returns the sequence of 1s and 0s. This sequence is sent to the program and presented as information you can read.

The writing process of solid state drives offers several benefits, such as the ability to use the drive while in motion, but the technology is subject to limitations. Most notably, each transistor can only be written to a certain number of times before it will no longer function. Each drive employs advanced methods, known as wear leveling, to prevent a particular section of the drive from premature wear. Even with wear leveling, solid state drives eventually need to be replaced as sections become unwritable.

Resources

• Popular Science: Solid State Technology