TAPE UNITS

These are not as common now as they were just a few short years ago. They were primarily used to back-up important data, especially in a business setting, but could be used to make a copy of your entire hard drive so you'd have an emergency copy of everything. Today, hard drives are so large that the tape units are not nearly as effective (the cassettes are generally too small) and the hard drives are so reliable that they are not really needed for normal operations. Also, Re-writeable CDs (CDRWs) have displaced tape units as the back-up unit of choice for most people as they allow allow larger backups (650 Mb vs 250 Mb)at a higher rate of speed than tape drives. Plus a CD allows random access to the data whereas a tape is a serial device.

It's important to understand that a tape unit uses magnetic media to store information, as does a hard drive or a diskette in a floppy drive. The difference is that a magnetic tape goes past the read-write heads in a long continueous stream whereas the read-write heads on a floppy/hard drive can move to anywhere on the surface of the spinning disk almost instantly. That's important when you need data. If it (the data) is on a tape, and happens to be towards the end of the tape, it will take a considerable amount of time to find and read the data. Because the read-write heads of a spinning disk (floppy or hard) can access the entire disk at the same rate of speed, it doesn't matter where (or how) the data is stored, it is always quickly available.

Another factor that makes tape units less desirable is the fact that tape becomes brittle over time. If a tape should happen to break, the data at the point of the break is lost forever. It has always been a good practice to replace cassette tapes pretty often, and make more than one copy of anything you need a back-up of. Because tapes are serial devices, companies tend to speed up the tape past the read/write heads to lower access times. The disadvantage to this is the stress it places on the tape when it speeds up or slows to a stop, and a brittle tape won't stand much stress at all.

See also Tape Drives

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