Floppy Disk
This is the least expensive type of removable backup, since all computers are equipped with a disk drive. Unfortunately, floppy disks do not hold enough information to easily back up most modern computers.

Removable Cartridges
Most new cartridge drives, such as SyQuest or Iomega Zip or Jaz drives, hold at least 1 GB of data, making them quite adequate for backing up individual computers. They also can access data very quickly, simplifying data retrieval. On the downside, cartridges tend to be fairly expensive, making the drives impractical for backing up many gigabytes of data.

Optical Drive
Optical or magneto-optical drives record on removable disks that hold anywhere from 650 MB to several GB of data. The fastest growing type of optical storage is the recordable CD drive, or CD-R, which allows you to record data onto a disc that can be played in any CD-ROM player. With CDs going for under $2, CD-R technology is an inexpensive and convenient form of backup. Re-writable drives, or CD-RWs, allow updating and deleting of files as needed. A re-writable CD goes for around $12. But since you can reuse a CD-RW disc several times, it will be less costly in the long run.