Usage and characteristics of USB flash drives
Flash drives are widely used as an auxiliary storage medium and for data backup and transfer between computers. Some of them hold operating system installation files to boot the computer.
A USB stick can have a capacity of up to 2 TB and, unlike some large rewritable data storage devices, such as external HDDs of 2 TB and more, requires neither an external power supply, nor batteries, as it derives the power directly from the device to which it’s attached via the USB port.
What makes a USB flash drive so convenient to use is its small size, versatility and the ability to retain data for a long period of time even being unplugged from a PC or other device. Still, thumb drives have a limited number of write-erase cycles: from 3,000-5,000 (devices based on the multi-level cell (MLC) technology) to 100,000 (those with a single-level cell (SLC) memory). Eventually, the memory cells begin to break down and that results in an unstable functioning and further failure of the device. However, this limitation does not apply to read cycles. And as for a USB connector, it is designed to withstand up to 1,500 cycles of insert-removal.
What are the essential components of a USB drive?
A regular USB drive consists of several basic components: a standard USB connector/plug used to connect it to another device and a printed circuit board that integrates a microcontroller with a small amount of RAM and ROM, a flash memory chip (or several chips) where the information is stored and a crystal oscillator that controls the data output. The circuit itself is hidden in a plastic or rubber case that is strong enough to resist dust, dirt and minor mechanical damages like scratches.
Main types of flash drives
Whereas the first flash drive had a capacity of only 8 MB, the capacities of modern ones range between 8 GB and 2 TB, depending on the manufacturer. In addition, these drives may have different USB specifications: 1.0, 2.0, 3.0 and 4.0. The newer the version, the higher the data transfer rate:
- USB 1.0 – 12 Mbit/s;
- USB 2.0 – 480 Mbit/s;
- USB 3.0, 3.1 Gen 1 and 3.2 Gen 1 – 5 Gb/s;
- USB 3.1 Gen 2 and USB 3.2 Gen 2 – 10 Gb/s;
- USB 3.2 Gen 2x2 – 20 Gb/s;
- USB 4 – up to 40 Gb/s.
Most of them feature backward compatibility: the later versions function with the previous ones. It means, for example, that you can plug a USB 2.0 device into a USB 3.0 port and it will function well, but at the speed of USB 2.0.
The majority of the drives have a standard type-A USB plug that can be inserted in a port on a regular personal computer, but there are also devices with other types of connectors (for example, mini and micro A, B or type-C).
Nowadays USB drives are often combined with keychains, watches, pens and other commonly used items. Some of them may have unusual designs and additional features such as fingerprint or password protection.