There are three major categories of near-line storage: magnetic disk, magnetic tape, and compact disc (CD). Magnetic disks include 3.5-inch diskettes, and various removable media such as the Iomega ZIP disk and the Syquest disk. Tapes are available in almost limitless variety. Examples of media in the CD category are CD recordable (CD-R), CD rewriteable (CD-RW), and digital versatile disc rewriteable (DVD-RW).
Near-line storage provides inexpensive, reliable, and unlimited data backup and archiving with somewhat less accessability than with integrated online storage. For individuals and small companies, it can be an ideal solution if the user is willing to tolerate some time delay when storing or retrieving data. Near-line storage media, when on the shelf, are immune to infection by online viruses, Trojan horses, and worms because the media are physically disconnected from networks, computers, servers, and the Internet. When a near-line storage medium is being employed to recover data, it can be write-protected to prevent infection. If an infected computer is used to write data onto a near-line storage disk, tape, or CD, the medium may also become infected. It is suggested that near-line storage media always be scanned with an anti-virus program before use.
Advantages of online storage over near-line storage include near-zero access delay, simultaneous availability to a large number of users, and ease of centralized management.