USB flash drives
by Marc Beck
A USB flash drive is a small and lightweight portable data storage device. This device is also known as USB drive, jump drive, key chain drive, pen drive, thumb drive, key drive, and memory stick. It is rewritable because it uses NAND type flash memory. (Wikipedia, 2007) The USB flash drive does not require rebooting when plugging it into a USB (Ultra Serial Bus) port, because it is plug-and-play capable. That means that the operating system automatically recognizes the devices and assigns it a drive letter. It can then be accessed like a hard drive or a floppy disk.
(www.mrgadget.com)
USB flash drives are most often used for backup personal files or to transfer data between computers (SearchStorage.com, 2007). They are often used by system and network administrators as well as PC repair technicians, who use them to hold software for system maintenance, troubleshooting, recovery, and virus detection. Flash drives can also be used to boot operating systems, replacing the boot floppy disk or live CD. (Wikipedia, 2007)
A USB flash drive consists of a male type-A USB connector that provides an interface to the host computer and a plastic casing that contains the circuitry. The circuitry is made up of three main parts: a USB mass storage controller, a NAND flash memory chip, and a crystal oscillator. The USB mass storage controller implements the USB host controller and provides a linear interface to block-oriented serial flash devices. It also contains a small RISC microprocessor and a small amount of on-chip ROM and RAM. The NAND flash memory chip stores the data. The crystal oscillator produces the device's main 12 MHz clock signal and controls the device's data output through a phase locked loop. (Wikipedia, 2007)
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USB connector |
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USB mass storage controller device |
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Test points |
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Crystal Oscillator |
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LED |
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Write-protect switch |
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Space for second flash memory chip |
Additionally to those main components, many flash drives have an LED that indicates data transfer and a write-protect switch. Some circuit boards provide extra space to include a second memory chip. This allows the manufacturer to use the same circuit board design for devices with different storage capacities. To protect the connector from static electricity, flash drives usually have a cover cap or the connector is retractable. Sometimes the cap is permanently attached and can swivel back. Either the cap or the main body may contain a hole to attach the device to a key chain or a lanyard for transportation.
The USB flash drive has many advantages over other forms of data storage. It does not require an external power supply and can retain data for up to ten years, (Woodward, 2004) even if it is not plugged in or it is left in a computer that is turned off. (SearchStorage.com, 2007) USB flash drives are not platform dependent and operate under any modern operating system such as MS Windows, Linux, Mac OS, and Unix. (Woodward, 2004) flash drives are slowly replacing the floppy, the Zip disk, and similar storage media because they are faster, more compact, hold more data and are also more reliable and are built more durable. (Woodward, 2004) Most computers are now manufactured without floppy drives, but every mainstream PC and laptop comes equipped with USB ports. (Wikipedia, 2007)
Flash drives can withstand abuse far better than mechanical drives. Some have even survived being submerged in water without damage or data loss and functioned without any problems after drying completely. (Wikipedia, 2007)
The flash drive's superiority over other storage media is made possible by its lack of moving parts inside. Mechanical parts such as motors and actuators require more power, are more prone to failure, add size and weight and can easily get damaged. (Wikipedia, 2007)
The biggest disadvantage of the USB flash drive is that is number of write-and-erase cycles is limited to several hundred thousand due to material fatigue. Also write operations will gradually slow when the devices ages. Windows Vista ReadyBoost, a feature that allows the use of some flash drives to augment RAM, will decrease the life expectancy of the flash drive considerably. This is also a problem when running application software or an operating system from a flash drive. Some developers have optimized their software by forcing it to store temporary files in the RAM instead of the flash drive. Another disadvantage is that flash drives are easily lost due to their small size. (Wikipedia, 2007)
(www.microsoft.com)
The USB port was designed in the mid-1990's to replace the serial and parallel ports. When USB 1.0 entered the market in 1996 there was no hardware available to use it and it was not fully supported by any operating system. USB came with two signaling rates: low speed with 1.5Mbps (Megabits per second) and high speed 12Mbps. Windows 95 had very poor USB support, but it improved with Windows 98. There were more USB devices available when USB 1.1 was released in 1998, but at that time it was still too slow for fast, portable mass storage media. This changed when USB 2.0 finally came out in 2000 with a third signaling rate of 480 Mbps. (Woodward, 2004)
At the same time as USB evolved, advances in microprocessor technology made it possible to build memory chips that were faster, smaller and cheaper and also had a lower power consumption. A company named Trek claims to be first to sell a flash drive in 2000 called Thumbdrive. The patent is however not specific enough and describes a number of similar devices. M-Systems had been working on flash drive since 1998 and was first to sell the product in North America in 2000. Their device was called DiskOnKey. IBM brought a 8MB flash drive out at around the same time and named it USB Memory Key. Also in 2000, Lexar introduced a compact flash card with an internal USB function. The earliest document to describe the invention of the flash drive accurately is from IBM and was written in 1999. All four companies claimed the invention as their own and there have been several lawsuits for patent infringement resulting in patents for each company in different countries. (Wikipedia, 2007)
Many flash drives have password protection or even more advanced security features. Some devices offer data encryption to prevent unauthorized people from accessing the data stored on them. Those drives, however, can only be accessed by computers with compatible encryption software. Another security feature is the write-protect mechanism that prevents the host computer from writing or modifying data on the drive. This is often used to repair virus infected computers without infecting the flash drive.
In some cases the flash drive itself is used as a security feature. Those flash drives contain encryption keys or communicate with the security software on the target machine, which is often programmed in such a way that it will not operate without the flash drive being plugged in. But flash drives can also pose a serious threat to security. Due to their small size they can easily be used to smuggle confidential data out or malicious software in without being detected.
The aforementioned security issues have a significant impact on companies, government agencies, and other organizations, which now have to spend a great amount of money and effort to prevent the use of flash drives for espionage or sabotage. As a temporary solution, some organizations either forbid the use of flash drives, disable the mounting of USB devices by users without administrator rights, or disconnect the USB ports. (Wikipedia, 2007)
Flash drives are often required as a backup medium for programming classes in college, because they are an easy way to transport large amounts of data. Almost every person who works with computers on a daily basis has now at least one flash drive.
Another common sight are portable media players that are smaller and have more storage capacity than ever before. Today's portable media players have basically evolved from flash drives. Some members of the Ipod family, like the iPod shuffle, are actually flash drives that were equipped with sound output and a simple user interface.
(www.bid4optics.com/.../new-ipod-shuffle-lg.png)
A flash drive can even serve as a live saver in case of stroke, heart attack, or accident. If the flash drive contains medical data about its owner, this data could be accessed by paramedics and doctors in an emergency and provide valuable data, for example if the person needs certain medications on a regular basis, or suffers from certain allergies or life threatening conditions. Especially elderly people can benefit from this technology. (medictag, 2007)
(www.criticalmedicalinformation.com/)
The use of USB flash drives also had an impact on my own life and changed the way how I store and transport data. I often repair other people's computers and many times I need to transfer files such as driver software or anti virus programs between two machines. I also needed to transfer papers that I had written on my own PC to the printer in the computer lab. At the beginning, I used floppy disks for those purposes. But when programs got bigger, floppy disks with only 1.44 MB of storage capacity were not sufficient anymore and besides that they did not last long and were very unreliable. A temporary solution was to e-mail files to my own e-mail address, but for that both computers have to be connected to the internet. Owning at least one flash drive has made life a great deal easier, since I can carry often used programs and a backup of all my files around with me on my key chain all the time. That is something that I could not do with a stack of floppy disks.
Works cited
SearchStorage.com. (2007). SearchStorage.com Definitions [Online]. Available: http://searchstorage.techtarget.com/sDefinition/0,,sid5_gci869057,00.html [2007, November 7]
Woodward, M. (2004). USB 2.0 Hi-speed Flash drive roundup Ars Technica the art of technology [Online]. Available: http://arstechnica.com/reviews/hardware/flash.ars [2007, November 9]
Wikipedia, (2007) USB flash drive Wikipedia [Online]. Available: http://en.wikipedia.org/wiki/USB_flash_drive
Medictag, (n. d.) [Online]. Medictag could truly save you. MedicTag Personal Emergency Information Available: http://www.medictag.com/