12.2 Backup Media
12.2.2 Magnetic and optical disks
Although tape has traditionally been the media of choice, new forms of backup media are starting to become popular including optical CD Recordable (CD-R) disks, and CD Re-writable (CD-RW) optical disks. Various forms of magnetic media such as removable hard drives,. Jaz™, and Zip™ disks are also becoming more common. Most of these backup media are not intended to back up large volumes of data, but they are a flexible alternative that is very fast and can be treated as another disk drive on the computer. Disk drives, whether magnetic or optical, have one characteristic in common: they are random access devices. Instead of advancing or rewinding, as with tape, they can seek and find the desired file in a fraction of a second. This makes them very flexible for backing up relatively small amounts of data (usually less than one or two Gigabytes). There are writable CD changers that can handle very large amounts of data with maximum flexibility; however, they are relatively expensive. Figure shows the variety of backup media available and Figure lists them in order of capacity.