Flash storage refers to any data storage device that utilizes the NAND type of flash memory. A standard flash storage system consists of two parts: a memory unit and an access controller. The memory unit allows the system to store data, while the access controller governs the access to the storage space. Typical examples of flash storage devices are solid-state drives and flash memory cards.
One of the advantages of flash storage is its energy efficiency. When compared to traditional hard drives, it consumes five times less power. It is also immune to wear since it lacks mechanical parts. However, the downside of flash storage is that write speeds are slower in comparison to traditional hard drives, particularly in the case of single-level cell devices. Additionally, it features a limited tolerance for write-erase cycles.
The NAND flash memory that flash storage devices employ operates by storing data in an array of memory cells comprised of floating-gate transistors. These transistors are arranged in a grid and feature two gates, unlike traditional transistors that only feature one. That allows it to retain voltage between the gates, making the stored data non-volatile, meaning it is retained even after a device powers down. The only way to remove the data is to drain the voltage between the gates by using a feature unique to flash memory.