Actually Authoring drives have a 4.7gb limit also. Commercial dvds are created via one of 2 methods. Either 1) the dvd contents are created then backed up to tape media or 2) contents are backups to 2 aurthoring disk (1 for each layer) these are then turned into the duplication house which presses the 2 layers together. At this time dual layer disk cannot be burned which means sadly that there is no such thing as a single sided 9gb disk.