Some file systems are designed to distribute usage over an entire memory device without concentrating usage on any part (e.g., for a directory) to prolong the life of simple flash memory devices. Some USB flash drives have this 'wear leveling' feature built into the software controller to prolong device life, while others do not, so it is not necessarily helpful to install one of these file systems.[39]
Flash memory combines a number of older technologies, with lower cost, lower power consumption and small size made possible by advances in microprocessor technology. The memory storage was based on earlier EPROM and EEPROM technologies. These had limited capacity, were slow for both reading and writing, required complex high-voltage drive circuitry, and could be re-written only after erasing the entire contents of the chip.
USB flash drives are only limited by the cost of the storage space and the physical constraints of the drive. Some of the cheaper flash drives can store less than a gigabyte, but modern high-end flash drives can store as much as 1TB of data, about equivalent to a typical hard drive. A standard external USB drive can store or backup around 64GB, 128GB, 256GB, or 512GB of data. As storage space increases, USB flash drives have become proficient at storing massive files such as ultra high-definition videos that display at 4K or even 8K resolution.
In the arcade game In the Groove and more commonly In The Groove 2, flash drives are used to transfer high scores, screenshots, dance edits, and combos throughout sessions. As of software revision 21 (R21), players can also store custom songs and play them on any machine on which this feature is enabled. While use of flash drives is common, the drive must be Linux compatible.
Some manufacturers, aiming at a "best of both worlds" solution, have produced card readers that approach the size and form of USB flash drives (e.g., Kingston MobileLite,[65] SanDisk MobileMate[66]) These readers are limited to a specific subset of memory card formats (such as SD, microSD, or Memory Stick), and often completely enclose the card, offering durability and portability approaching, if not quite equal to, that of a flash drive. Although the combined cost of a mini-reader and a memory card is usually slightly higher than a USB flash drive of comparable capacity, the reader + card solution offers additional flexibility of use, and virtually "unlimited" capacity. The ubiquity of SD cards is such that, circa 2011, due to economies of scale, their price is now less than an equivalent-capacity USB flash drive, even with the added cost of a USB SD card reader.
These products use flash memory chips, a stable, high-density storage medium, to hold your data. They pack a huge amount of information into a compact form factor. Most thumb drives are less than 2 inches long and easily fit in a pocket, laptop bag or purse. Models with built-in covers protect physical connectors from damage, and select products feature rugged silicon and metal shells that enhance heat and water resistance.