Pen drive

The USB flash drive (Universal Serial Bus), also known by the local names: memory stick, finger b>, skewer, USB stick, external memory, pendrive, memocapsule, memorin or mayan key, is a type of data storage device that uses solid-state circuits to store data and information.

History

IBM DiskonKey USB memory

First generation

The companies Trek Technology and IBM began selling the first USB flash drives in 2000. Trek sold a model under the trade name Thumbdrive, and IBM sold the first drives in North America under the DiskOnKey brand name., developed and manufactured by the Israeli company M-Systems in capacities of 8 MB, 16 MB, 32 MB and 64 MB. These were promoted as the "true floppy disk replacements", and their design continued up to 256 MB. Earlier models of this device used batteries, instead of power from the PC.

Second generation

SD card reader, which acts as USB memory.

Within this generation of devices there is connectivity with the USB 2.0 standard. However, they do not fully use the 480 Mbit/s transfer rate supported by the USB 2.0 Hi-Speed specification, due to the technical limitations of NAND-based hard drives. The fastest devices of this generation use a dual-channel controller, although they are still a long way from the transfer rate possible from a current generation hard drive or the maximum performance of high-speed USB.

File transfer speeds vary considerably. Most common fast drives are claimed to be able to read at speeds of up to 480 Mbit/s and write at roughly half that speed. This is approximately 20 times faster than USB 1.1 devices, which have a maximum speed of 24 Mbit/s.^{[citation needed]}

Third generation

The USB 3.0 standard offers vastly improved data exchange rates compared to its predecessor, along with backwards compatibility with USB 2.0 ports. The USB 3.0 standard was announced in late 2009, but consumer devices did not become available until early 2010. The USB 3.0 interface features transfer rates of up to 4.8 Gbit/s, compared to 480 Mbit/s of USB 2.0. Even though the USB 3.0 interface allows for very high transfer data rates, as of 2011 most USB 3.0 Flash drives do not use the full speed of the USB 3.0 interface due to limitations of their memory controllers, although some memory channel controllers come on the market to solve this problem. Some of these flash drives hold up to 256 GB of memory (which is 1024 times larger than M-Systems' initial design). There are also devices that, apart from their usual function, have a USB memory as an included accessory, such as some wireless optical mice or USB memories with slots to recognize other types of storage (microSD, m2, etc.).

In August 2010, Imation announced the market launch of the new line of secure USB flash drives Flash Drive Defender F200, with capacities of 1 GB, 2 GB, 4 GB, 8 GB, 16 GB; 32GB and 64GB. These storage units have an ergonomic biometric sensor based on a physical support that corroborates the matches of the identification fingerprints, before allowing access to the information.

Overview

Early models required a battery, but today's models use electrical power from the USB port. These USB flash drives are resistant to (external) scratches, dust, and some even water, factors that plagued previous forms of portable storage, such as floppy disks, compact discs, and DVDs.

Their great success and diffusion have given them various popular denominations related to their small size and the various forms of presentation, none of which has been able to stand out among all of them. The qualifier "USB" or the context itself allows easy identification of the computing device to which it refers; Although being a bit strict in terms of the concept, USB only refers to the relevant connection port.

Features

These USB memories have become the most widely used personal data storage and transport system, displacing traditional floppy disks and CDs in this use. USB sticks of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 GB, and up to 1 TB (1024 GB) can easily be found on the market. USB sticks with higher capacities can still be, due to its price, outside the range of the "domestic consumer". This is at least the equivalent of 180 700MB CDs or approximately 91,000 1440KiB floppy disks.

Support

Current operating systems can read and write USB flash drives simply by plugging them into a USB socket on the computer that is turned on, receiving the power supply through the connector itself, 5 volts and a consumption of 2.5 W as maximum. On older computers (for example: Windows 98 computers) you need to install a driver provided by the manufacturer. The various GNU/Linux distributions also have support for these storage devices since kernel version 2.4.

Utilities

Inside a USB memory.

USB sticks are common among people who transport data from home to work, or vice versa. Theoretically they can retain the data for about 20 years and be written to up to a million times.

Although they were initially designed to store data and documents, it is common to find programs or files of any other type on USB flash drives because they behave like any other file system.

The new U3 devices for Microsoft Windows integrate an applications menu, similar to the "Start" menu itself, which allow you to organize image files, music, etc. For USB sticks from other manufacturers, there are also collections based on free software, such as PortableApps.com.

The availability of USB flash drives at reduced costs has caused them to be widely used for promotional purposes, especially in areas related to the computer industry (for example, in technological events). They are often given away for free, sold below cost, or included as a free bonus with the purchase of another product.

Usually, these devices are personalized by engraving the company logo on the surface of the USB flash drive casing, as a way of increasing brand visibility. The USB memory may contain no data or preloaded information (graphics, documentation, web links, Flash animations or other multimedia files, free applications or demos). Some preloaded USB flash drives are read-only; others are configured with two partitions, one read-only and one where data can be included and deleted. USB sticks with two partitions are more expensive.

USB flash drives can be configured with the autorun function for Microsoft Windows, whereby inserting the device automatically boots a specific file. To activate the autorun function it is necessary to save a file called autorun.inf with the appropriate program in the root directory of the device. The autorun function does not work on all computers. Sometimes this functionality is disabled to hinder the propagation of viruses and Trojans that take advantage of this boot system.

USB memory Windows To Go.

Another utility of these USB flash drives is that, if the computer's BIOS supports it, they can boot an operating system without the need for a CD, DVD or even a hard drive. Booting from USB memory is widespread on new computers and is faster than with a DVD-ROM drive. You can find Linux distributions that are completely contained on a USB stick and can boot from it (see Live CD).

High-capacity USB sticks, as well as hard drives or CD/DVD burners are an easy way to make a backup, for example. There are CD-ROM, DVD, floppy, or Zip drives and writers that connect to the USB port.

In addition, since 2008, there are stereos with a USB port to which a USB memory can be connected to play the music contained in it.

As a security measure, some USB flash drives have the ability to prevent writing using a switch. Others allow you to reserve a part to hide it by means of a key.

Strengths and Weaknesses

Despite their low cost and long warranty, it must be borne in mind that these storage devices can suddenly stop working due to various accidents: voltage variations while they are connected, due to falls from a height greater than one meter, due to its prolonged use for several years especially in old USB sticks.

Flash drives are immune to the scratches and dust that plagued earlier forms of portable storage like compact discs and floppy disks. Its durable solid-state design means that in many cases it can survive the occasional abuse (bumps, drops, steps on it, being run through the washing machine or splashed liquids). This makes it ideal for transporting personal data or work files that you want to access in multiple locations. The near ubiquitousness of USB support on modern computers means that a device will work just about anywhere. However, Microsoft Windows 98 does not support generic USB mass storage devices, you must install a separate driver for each manufacturer or else get generic. For Microsoft Windows 95 such drivers are almost non-existent.

Flash drives are a relatively dense form of storage, even the cheapest device will store as much as dozens of floppy disks, and for a moderate price they match or exceed CDs in size. Historically, the size of these drives has ranged from several megabytes to a few gigabytes. In 2003 the drives were running at USB 1.0/1.1 speeds, about 1.5 Mbit/s or 12 Mbit/s. Devices with USB 2.0 interfaces are released in 2004. Although USB 2.0 can deliver up to 480 Mbit/s, flash drives are limited by the bandwidth of the internal memory device. Therefore read speeds of up to 100 Mbit/s are achieved, making write operations a bit slower. Under optimal conditions, a USB device can retain information for about 10 years.

USB flash drives implement the "USB mass storage device class" (class of USB mass storage devices). This means that most modern operating systems can read or write to such drives without additional drivers. Instead of exposing the complex technical details behind it, flash devices export a logical block-structured unit of data to the host operating system. The operating system can use whatever file system or block addressing scheme it wants. Some computers have the ability to boot from USB sticks, but this ability depends on the BIOS of each computer, and for this, the drive must be loaded with an image of a boot disk.

USB sticks can withstand a finite number of read/write cycles before failing. With normal use, the average range is around several million cycles. However, write operations will become slower as the drive ages.

This should be taken into account when using a flash device to run software or an operating system from them. To handle this (in addition to space limitations on common drives), some developers have released versions of operating systems such as Linux or common applications such as Mozilla Firefox specially designed to run from flash drives. This is accomplished by reducing the size of the swap files and storing them in RAM.

Use Considerations

The care of USB memories is the same as that of electronic cards and video game cartridges: avoid falls or bumps, humidity, magnetic fields and extreme heat.

In the past, in the earliest devices of this technology, it was advised to "Unmount the drive" or "Safely remove hardware " from the "Device Manager" in Windows or "Eject" on Mac OS. On some systems the write is done in a lazy way (this means that the data is not written at the moment) through a write cache to speed up the write times and so that the system finally writes "once. one time" when the write cache is full, but removing the drive before the system saves the write cache contents may cause discrepancies in the existing file system on the USB stick which could lead to data loss.

To reduce the risk of data loss, write caching is disabled by default for external drives in Windows operating systems starting with Windows XP, but a write operation can still take several seconds and will not be processed. you must physically unplug the drive until it is completely finished, otherwise the data to be written will be lost. Even if the USB memory is not damaged, the affected files may be difficult or even impossible to recover, in some cases requiring a complete deletion or formatting of the file system to be able to use it again. So extracting you have to be careful on writing, but extracting it on reading would be irrelevant.

In Windows systems (2000 ~ XP with Service Pack 2) with mapped network drives, it may happen that when you connect the USB stick, the system does not provide you with a letter previously in use. In this case, you will have to go to the disk manager (diskmgmt.msc), locate the USB memory and manually change the drive letter.

In Windows XP, it may be the case that if the USB stick is not disconnected using the Safe Remove function, Windows may automatically mark the USB stick as problematic and disable it, and it is the case that the USB stick can be used in other computers but not the one marked as problematic. You have to enter the Device Manager and re-enable it.

• USB memory applications:
  • Save encrypted files.
  • Store portable applications (occupy less space, and run without prior installation).
  • Install an operating system from flash memory.
  • External and additional storage for portable devices (mobile phones, electronic books, external media player, etc.).

Components

Primary components

The most common parts of a USB memory are the following:

• A male USB connector type A (1): Provides the physical interface with the computer.
• Mass storage USB controller (2): Implement the USB controller and provide the homogeneous and linear interface for block-oriented serial USB devices, while hiding the complexity of block orientation, block removal and wear balance. This controller has a small RISC microprocessor and a small number of RAM and ROM circuits.
• Flash NAND memory circuit (4): Stores the data.
• Crystal Oscillator (5): Produces the device's main clock signal to 12 MHz and controls data output through a closed-phase-locked loop.

Additional components

A device may also include:

• Bridges and Test Points (3): Used in tests during unit manufacturing or for code loading within the processor.
• Leds (6): Indicate data transfer between device and computer.
• Write Protection Switch (7): Used to protect data from writing or erasing operations.
• Free space (8): A space is available to include a second memory circuit. This allows manufacturers to use the same printed circuit for devices of different sizes and thus respond to market needs.
• USB connector cap: Reduces the risk of damage and improves the appearance of the device. Some units do not have a lid but have a retractable USB connection. Other devices have a rotating cap that never separates from the device and avoids the risk of losing it.
• Transport Help: In many cases, the cap contains a suitable opening for a chain or necklace, however this design increases the risk of losing the device. For this reason many others have such an opening on the body of the device and not on the lid, the disadvantage of this design is that the chain or necklace is attached to the device while connected. Many designs bring the opening in both places.

Related Technologies

USB 3.0

Introduced in 2008, it is in full swing as the transition between USB 2.0 and USB 3.0 devices. The main technical novelty of the USB 3.0 port is that it increases the transfer capacity to 4.8 Gbit/s (600 MB/s), which is currently 480 Mbit/s. Internal copper cabling will be maintained to ensure compatibility with USB 1.0 and 2.0 technologies.

If in USB 2.0 the cable has four lines, a pair for data, one for current and one for grounding, in USB 3.0 five lines are added. Two of them will be used for sending information and another two for receiving, in such a way that bidirectional traffic is allowed, in both directions at the same time. The increase in the number of lines makes it possible to increase the transmission speed from 480 Mbit/s to 4.8 Gbit/s.

The amount of current carried by a USB 1.0 and 2.0 cable is often insufficient to recharge some devices, especially if we use hubs where several of them are connected. In USB 3.0, the intensity of the current is increased from 100 milliamps to 900 milliamps, with which batteries can be charged at a higher speed or power other components that require more power. This increase in intensity could bring with it a lower energy yield. But thinking about it, USB 3.0 uses a new interrupt-based protocol, as opposed to the old one that relied on periodically polling devices.

The increase in lines in USB 3.0 causes the cable to be slightly thicker, a major drawback. If until now the cables were flexible, with the new standard they have a thickness similar to the cables used in Ethernet networks, being therefore more rigid.

Just like between USB 1.1 and USB 2.0, compatibility is guaranteed between USB 2.0 and USB 3.0, thanks to the use of similar connectors, whose additional contacts are placed in parallel, so that they do not affect when using a port that not be of the same type.

Care

• Before using a USB memory, you have to format, for example with the exFAT format, which is more resistant and efficient than FAT16 and FAT32 formats. If memory is to be used on other devices such as mini-components, video-recorders or radiators, it is preferable to use the FAT32 format for better compatibility with these machines, but taking into account that this format does not support files with a size greater than 4 GB each and is not compatible with capacity memories greater than 32 GB.
• Direct exposure to the sun should be avoided and excess moisture may degrade memory and, in extreme cases, cause the loss of information. Likewise, you must be careful of blows and falls, by the detachment of the welds.
• It is normal for memories to warm up a bit while being used, but if they are overheated they can cause flaws that would damage the information.
• It is always advisable to disassemble the USB memory or run the "safe drive" before disconnecting it, since it is possible that the data are read, for example by antivirus programs or the system in memory, which could damage the information.
• It is advisable to use a USB stick vaccine application to protect computer virus infections and equipment.
• With programs like H2testw and or MS-DOS command CHKDSK /x /r damaged sectors are sought; the sectors damaged in USB sticks cannot be repaired or marked as defective to the Operating System, the USB memory should be replaced immediately, or require the help of an Engineer.