Comparing Disk, Tape, and Flash Memory Technologies

Several types of removable-media disk drives are commonly used. Traditionally, the most common varieties have used magnetic media, but some use one of two combinations of magnetic and optical storage: floptical or magneto-optical. Floptical and magneto-optical media drives encode information on disk by using different combinations of laser and magnetic technologies.

Flash memory devices, which have largely replaced the floppy disk for data transfer, emulate disk drives and are discussed in this chapter. Some tape drives are also capable of emulating disk drives by providing drive letter access to a portion of the media, but these drives are used primarily to perform streaming backups of large disk drives and network drive arrays.

Magnetic Disk Media

Whether you are looking at "pure" magnetic media, floptical media, or magneto-optical drives, all types of magnetic disk media share similar characteristics. Disk media is more expensive per megabyte or gigabyte than tape, usually has a lower capacity, and is more easily used on a file-by-file basis as compared to tape. Disk media uses random access, which enables you to find, use, modify, or delete any file or group of files on a disk without disturbing the rest of the disk's contents. When used as a backup medium, most types of disk media are faster for copying a few files but are typically slower for copying large numbers of files or entire drives.

Magnetic Tape Media

Tape media has much less expensive costs overall per megabyte or gigabyte than disk media, has a higher total capacity, and is more easily used on an image or multiple-file basis. Tape drives use sequential access, meaning that the contents of a tape must be read from the beginning and that individual files must be retrieved in the order found on the tape. Also, individual files usually can't be modified on the tape or removed from the tape; the contents of the entire cartridge must be deleted and rewritten. Thus, tape drives are more suited for complete backups of entire hard disks including all applications and data. Because it is suited for mass backup, tape can be difficult to use for copying single files.

Note

Removable-media disk drives can be used as system backup devices similar to tape. However, the higher price of the medium itself (disks or cartridges) and the generally slower speed at which they perform can make this use somewhat prohibitive on a large scale. For file-by-file backups, disk media is ideal; if, however, you're completely backing up entire drives or systems, tape is faster and more economical.

Flash Memory Media

The newest type of removable storage is not magnetically based but uses flash memorya special type of solid-state memory chip that requires no power to maintain its contents. Flash memory cards can easily be moved from digital cameras to notebook or desktop computers and can even be inserted into photo printers or self-contained photo display devices. Flash memory can be used to store any type of computer data, but its original primary application was digital photography. However, more and more digital music players have removable flash memory cards, and so-called thumb or keychain flash memory devices that plug directly into a USB port are helping to make flash memory a mainstream storage medium and an increasingly popular replacement for some types of magnetic removable-media storage, particularly floppy disks, Zip drives, and SuperDisk drives.

Tip

Literally dozens of removable storage devices are currently on the market. Be sure to compare your chosen solution against the competition before making a final purchase. Be especially wary of missing statistics in press releases and product packagingmanufacturers are apt to omit a specification if their drives don't measure up to the competition.