Compared to CDs, which hold 700 megabytes, and floppy disks, which can typically store 1.44MB, DVDs are capable of storing huge amounts of data -- about 4.7 gigabytes. There are several different types of DVD formats, the most common being DVD-RW and DVD-R.
Both formats are recordable, but the DVD-R was the first type to become available and was designed to be recorded on only once. The “R” stands for “recordable,” to differentiate them from normal read-only DVDs, called DVD-ROMs. A DVD-RW can be recorded, erased and re-recorded many times.
Because DVD-R discs are designed for one-time use, they are generally cheaper. Since they are meant to be recorded only once, they are sold in bulk, in quantities of 25, 50 or 100 discs. DVD-RW discs are more expensive to produce and are frequently sold in much smaller quantities -- a pack of five is common.
Because DVD-R discs are so inexpensive, they are used for the same sort of jobs CD-Rs and floppy disks once performed, such as copying data for a friend or coworker. As programs and data files have become larger, DVD-Rs are a more practical medium for sharing information among users than CDs or floppy disks. Computer manufacturers have enabled this type of use by installing DVD recorders in most new computers.
DVD-R for Archiving
While the ability to reuse DVD-RW discs may seem to be a great advantage, this is not always true. DVD-R discs are best for permanent records. The medium is inherently more stable because there is less “flexibility” in the disc’s makeup. In addition, the more stable nature of DVD-Rs makes them compatible with a wider variety of DVD players. This is especially useful if you are burning your home movies to DVD and want to share them with friends.
DVD-RW for Backups
Because DVD-RW discs can be recorded and re-recorded as many as a thousand times, they are used for system backups. Their enormous capacity -- some of the double-sided discs can hold nearly 10GB -- makes them appropriate for the kind of large-scale backup operation required by the large hard drives on modern PCs. The permanence of the DVD-R makes it unsuitable for this purpose, and DVD-RWs are a more cost-effective approach.
- dvd image by Jaimie Duplass from Fotolia.com