Storing backups on optical media such as DVD-R discs suffers from two major drawbacks: DVD discs are easy to scratch, and the media itself degrades after a while. You can deal with the scratching issue by careful handing of the media, but even expensive media becomes unreadable over time. Dvdisaster aims to help you recover the information off scratched and aged media.
Dvdisaster takes any ISO image and generates a file containing error correction information, which you can burn to the DVD along with the image or store separately on other media. (In order to protect the error correction information itself from scratches and aging, it must be a larger percentage of the overall disc if you burn it to the DVD than if it stays separate.) The error correction file is about 15% the size of the ISO by default, or 700-odd megabytes for a typical DVD. When you want to recover media that is old or scratched, dvdisaster uses this error correction information to regain the original information.