The DVD RW is also known as DVD-RW, DVD+RW, or erasable DVD. This disc is similar to the CD-RW, whereby information can be recorded to the disc, erased, and then the disc reused.
There are two different versions of erasable DVD: -RW and +RW formats. There are some technical differences in these formats (see the DVD-R and DVD+R page) and the +RW is supposed to provide drag and drop file saving and deleting.
The -RW format seems to provide better compatibility over a wider range of drives. Despite the differences, for the average user the formats are used interchangeably.
The structure of the DVD RW disc and the way it stores the information is similar to the CD-RW. It uses a phase change material as the information storage layer and the laser light is able to change the form of this material depending on whether the disc is being recorded to or being erased. More information can be found at the CD-RW page.
Like other DVDs, the erasable DVD is two discs sandwiched together. The bottom disc has the full structure as discussed in the CD-RW page.
However, the disc is only 0.6 mm thick which is half the thickness of the CD-RW disc (1.2 mm). An adhesive is placed on top of the 0.6 mm disc and then another 0.6 mm disc is glued to it and then a label is screened on top of this disc. This brings the total disc thickness to 1.2 mm, which is the same as the CD. Because the erasable DVDs are only available in the single layer format (only one information layer that can store information) the top disc is simply a blank or dummy polycarbonate plastic disc with none of the other layers.
The storage capacity of the DVD-RW and DVD+RW media is 4.7 GB and the maximum recording speed is 8x. These discs may be useful for transferring large files from one computer to the next or from person to person, but they are not recommended for the long-term storage of digital scrapbooking projects or other types of digital information. Tests have shown that these discs are unstable and can fail or not function properly in only a short amount of time.