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How Do USB Flash Drives Work?

written by: •edited by: Rebecca Scudder•updated: 12/8/2009

USB flash drives are a popular portable storage device that have quickly taken over the market—almost everyone seems to have one or two. But how exactly do USB flash drives work? Here's an overview.

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    What Is A Flash Drive?

    If you aren't quite sure what a flash drive is, then here's a quick primer. Basically, flash drives, sometimes referred to as jump drives, are a type of portable memory storage device. They are extremely compact, usually smaller than the size of your thumb - hence another name, "thumb drive" - yet can contain fantastic amounts of data—a number that just keeps on increasing, with 128 GB flash drives just on the horizon.

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    SSD: Solid State Drives

    A flash drive is a type of drive known as an SSD, or solid state drive. Basically, this means that the drive has no moving parts, making it faster, more durable and more reliable than the traditional spinning disk hard drive. (“Drive” is a bit of a misnomer when it comes to flash drives, or any SSD, as nothing actually moves.) Inherent to all SSD drives, including flash drives, is a gradual slowdown and corruption of the drive.

    More specifically, flash drives use a type of memory called NAND flash—hence the name. This is a non-volatile memory, that is, one that does not require power to maintain it. Some flash drives also come with a small amount of volatile RAM memory to use as a cache.

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    From Drive To Drive: USB

    A flash drive transfers data via a USB port to another device, typically a computer hard drive. Flash drives use the male connector, typically type A. The corresponding female USB drives are found on almost every mainstream computer and laptop, as well as the required USB drive support.

    The latest, USB 2.0, has been adopted for almost all modern flash drives. However, USB drives cannot run at the max speed of USB 2.0 due to their use of NAND flash memory, which inherently cannot run faster than 30 MB/s out of the potential 60 MB/s—still faster than 1.0 speeds of 1 MB/s, but not quite up to full capacity.

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    File System

    Most flash drives are formatted with either the FAT or FAT 32 file system. Because FAT is so commonly used, this means that the file system is compatible with a variety of operating systems and utilities, including many popular file recovery programs.

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    Software & Algorithms

    Flash drives are often preloaded with software, sometimes security ones such as encryption and the like, or sometimes software that is specific to the device. Flash drives used for MP3 devices, for instance, will often have music playback decoders preinstalled. There are many programs that can be run off of a flash drive, from tiny Linux OSs like Linux Mint or Puppy Linux to some freeware open source programs such as VLC or GIMP.

    Increasingly, flash drives come preloaded with two algorithms to help lengthen their lifetime. The first is a “wear leveling” algorithm, that is, something that writes & erases evenly across the entire drive. The second is a sort of “write combining”, which decreases the number of writes required on the drive.

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    The Case

    Flash drive circuitry can be contained within a variety of mediums, though plastic is generally used. This makes up the bulk of the small size of the flash drives. The USB connector itself is either retractable or has a lens cap of some sort for further protection. The case will often include some sort of hole through it for storage purposes—flash drives are notoriously easy to lose, so keeping it on a lanyard or keychain is a good idea.

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    Bits & Pieces

    Some other knickknacks may also be included on the flash drive. Many will have LED lights to indicate whether the drive is connected or not. Write protection switches are another popular add-on, for the easy option of putting the drive in write-protection mode. Some even have an additional feature of being a memory card reader for other types of portable storage.