DVD Disks

Today DVD's have become the norm, they can hold about 8 times as much information as a CD but they don't cost 8 times as much. A standard DVD will hold up to 4.7 GB worth of data and 120 minutes worth of Audio/ Video as with CD's you can get larger capacity disks, they're called Dual Layer or Double Layer disk, they are twice as big as a standard DVD they can hold up to 8.5 GB of data or 240 minutes of Audio/ Video. Also like CD's you can get re-writable DVD which can be re-written time & time again.
All disks have a guaranteed writing speed, CD's tend to be able to be written up to 52 speed, the speeds are based on fractions of hours, so in theory a 52 speed CD written via your writing software and if your CD/DVD writer supports that speed, it should write the actual data in about 80 seconds or so. A DVD works in the same way, a DVD written at 4 speed should write the disk in about 15 minutes.
However in the real world it's nearer 3 or 4 minutes to write a CD and 17 minutes for a DVD, this is due to the disks needing a lead in and lead out track of the disks, so a CD/ DVD Rom or CD Player knows what's on the disk and what to do with it.