Magnetic tape is a medium for magnetic recording, made of a thin magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders. A device that stores computer data on magnetic tape is a tape drivOver years, magnetic tape can suffer from deterioration called sticky-shed syndrome. Caused by absorption of moisture into the binder of the tape, it can render the tape unusable.
One of the key advantages of magnetic tape is its capacity for holding data. Magnetic tape was the first medium able to hold a feature-length movie on a small, inexpensive device, thus enabling the home video market of the 1980s. In addition, compact cassettes can hold music on both sides, giving them a 90-minute total playing time, which is even greater than most CDs.
Magnetic tape is also easy to edit using a traditional linear-editing system.
This can involve duplicating a portion of a tape to a master reel, or physically cutting the tape and attaching the desired portions together with glue, splicing cement or adhesive tape. Editing in this manner requires no special computer equipment and may be less expensive and/or easier to learn than nonlinear digital editing.
One of the disadvantages of magnetic tape is generation loss, which refers to the fact that each successive copy of a tape loses quality compared to the original.
This can make it difficult to use magnetic tape for editing-intensive projects, or when extremely high fidelity is important. Digital media, on the other hand, can be copied and reproduced indefinitely with no visible or audible difference between the original and any of its copies.
Another problem with magnetic tape is its tendency to stretch out over time, causing the quality of the data to deteriorate. On old video tapes, this generally appears in the form of poor audio, and picture data can eventually suffer as well. Over time magnetic tape acquires a layer of magnetic debris from recording and playback heads, which may need to be cleaned periodically to continue functioning.
The mechanical complexity needed to use magnetic tape is another disadvantage of the medium. Items like cassette and VHS tapes include two separate reels, as well as a mechanism for exposing a small portion of the tape inside a player or recording device. Reel-to-reel tape players use multiple motors and moving parts, each of which is susceptible to mechanical failure. In the realm of digital media, flash-based memory uses no moving parts, thus eliminating this problem.
February 27, 2012
Compared to hard drives, flash drives use little power, have no fragile moving parts, and for most capacities are small and light. Data stored on flash drives is impervious to mechanical shock, magnetic fields, scratches and dust. These properties make them suitable for transporting data from place to place and keeping the data readily at hand. Flash drives also store data densely compared to many removable media. In mid-2009, 256 GB drives became available, with the ability to hold many times more data than a DVD or even a Blu-ray disc, Most personal computers support USB as of 2010. Flash drives implement the USB mass storage device class so that most modern operating systems can read and write to them without installing device drivers. The flash drives present a simple block-structured logical unit to the host operating system, hiding the individual complex implementation details of the various underlying flash memory devices.
The operating system can use any file system or block addressing scheme. Some computers can boot up from flash drives. Specially manufactured flash drives are available that have a tough rubber or metal casing designed to be waterproof and virtually “unbreakable”. These flash drives retain their memory after being submerged in water, and even through a machine wash. Leaving such a flash drive out to dry completely before allowing current to run through it has been known to result in a working drive with no future problems. Channel Five‘s Gadget Show cooked one of these flash drives with propane, froze it with dry ice, submerged it in various acidic liquids, ran over it with a jeep and fired it against a wall with a mortar. A company specializing in recovering lost data from computer drives managed to recover all the data on the drive. All data on the other removable storage devices tested, using optical or magnetic technologies, were destroyed.
Like all flash memory devices, flash drives can sustain only a limited number of write and erase cycles before the drive fails.[unreliable source?] This should be a consideration when using a flash drive to run application software or an operating system. To address this, as well as space limitations, some developers have produced special versions of operating systems (such as Linux in Live USB) or commonplace applications (such as Mozilla Firefox) designed to run from flash drives. These are typically optimized for size and configured to place temporary or intermediate files in the computer’s main RAM rather than store them temporarily on the flash drive. Most USB flash drives no longer include a write-protect mechanism, although a small number have a switch on the housing of the drive itself to keep the host computer from writing or modifying data on the drive. Write-protection makes a device suitable for repairing virus-contaminated host computers without risk of infecting the USB flash drive itself. A write-locked SD card in a USB flash card reader adapter is an effective way to avoid any writes on the flash medium.
The SD card as a WORM device has an essentially unlimited life. A drawback to the small size is that they are easily misplaced, left behind, or otherwise lost. This is a particular problem if the data they contain are sensitive (see data security). As a consequence, some manufacturers have added encryption hardware to their drives—although software encryption systems which can be used in conjunction with any mass storage medium achieve the same thing. Most drives can be attached to keychains, necklaces and lanyards. The USB plug is usually fitted with a removable and easily lost protective cap, or is retractable. USB flash drives are more expensive per unit of storage than large hard drives, but are less expensive in capacities of a few tens of gigabytes as of 2011 Maximum available capacity is increasing with time, but is less than larger hard drives. This balance is changing, but the rate of change is slowing..
Most USB based flash technology integrates a printed circuit board with a metal tip which is simply soldered on. As a result the stress point is where the two pieces join. Some manufacturers quality control does not ensure a proper solder temp further weakening the stress point. Since many Flash Drives stick out from a users laptop or PC they are likely to be bumped repeatedly in their life time and may break at the stress point. Most of the time a break at the stress point results in permanent damage to the printed circuit board where the joint is torn from the circuit. However, some manufacturers produce discreet flash drives that do not stick out and others use a solid metal uni-body that has no easily discernible stress point.