The following four chapters cover standard floppy disk drives, high-capacity "super" floppy disk drive replacements, removable hard drives, and tape drives, all of which are characterized as removable magnetic storage devices. These devices use media that can be swapped in and out of the drive, versus hard disk drives, whose media are a fixed part of the drives themselves. Although they are typically slower at accessing data than hard disks?sometimes much slower?removable magnetic storage devices are useful because you can store an unlimited amount of data on additional cartridges, albeit with only a subset of the data available online at any one time. Because media are separate items, you can transfer data between computers that are not networked, if those computers are equipped with a compatible drive. Removable media also allow storing data off-site as protection against fire, theft, or other catastrophes.
A major drawback of removable magnetic storage is inherent: magnetic storage is less reliable than optical storage. Over time, zero bits and one bits stored as magnetic domains tend to become an unreadable blur. A less obvious drawback of magnetic versus optical storage is the proprietary nature of most magnetic drives and media, and the continually changing standards. Try, for example, to read data written only five years ago to a proprietary DC600 tape drive. The original drive is dead, the manufacturer no longer exists, and the software used to write the data won't run on anything later than Windows 3.1 anyway. Even something as simple as reading data from a 5.25-inch floppy diskette can turn into a major undertaking. Accordingly, the most appropriate uses of these drives are to provide supplemental working storage, to transfer large amounts of data between computers, and to make backups. They are unsuitable for long-term data archiving.
Removable magnetic storage devices differ in many respects, including drive cost, storage capacity, and access time. Perhaps the most important difference is the cost of media, both per cartridge and per megabyte stored. When selecting a removable magnetic storage device, always keep in mind that media cost over the service life of the drive may greatly exceed the cost of the drive itself, particularly for drives that use proprietary, patented, and/or licensed media. Many of these drives are marketed on the King Gillette model of giving away the razor and selling the blades. The cost of those blades can really add up.
A floppy disk drive (FDD) is so called because it records data on a flexible circular plastic disk coated with ferrite or some other magnetic medium. This plastic disk is enclosed within a protective sleeve or cartridge. This assembly is called a floppy disk or a diskette. FDDs have been manufactured to accept 8-, 5.25-, and 3.5-inch diskettes, although only the last is still in common use.