DVD-9 is a type of Digital Versatile Disc (DVD) that has two storage layers on one side, the upper layer of which is semi-transparent. Such DVDs are referred to as Single Sided / Dual Layer. The storage capacity is up to 8.5 GB. If such a DVD-9 has storage layers on both sides, it is a double sided / dual layer version. The storage capacity doubles to 17 GB. The designation DVD-17 is correspondingly.