The only DVD-R drives (or media) I've seen are 4.7 GB. They definitely only write on one side, so it might be possible that there are discs you could flip over (hmmm... flashbacks to Apple ][s and hole punchers....), but I've never seen any. The DVD standard allows for dual-layer discs that actually have two recording surfaces on each side of equal capacity, making a total of about 9GB (about 17GB if you take both sides into consideration), but no current consumer-level DVD-R drive (or media) supports dual-layer. Almost all (if not all) commerical DVDs (movies, that is) are recorded dual-layer, so the drives can read them, just not write them.