Optical drives, such as DVD drives, store and read data with light. Small bumps or discoloration on a disc are read with a laser beam.
Optical drives can read from or be written to. Consequently, they can store documents and backups. However, optical drives can be specified as Read -only media so that data can only be read and can’t be deleted or written to. Read-only media is common for movie distribution, such as Blockbuster film DVDs.
Optical drives disks have limited storage sizes. At most, dual layer Blu-ray Discs can hold 50 GB.
CD drives have a speed rating. The first CD drives read data at 150 KBps, which is now referred to as 1x speed. CD drives now have speeds that are multiples of the 150KBps. For example, you may have a CD with a 72x speed which means 10,800 KBps. A writeable CD drives will have 3 numbers for the speed such as 52x24x16 which indicates a speed of 52x for read, 24x for write, and 16x for rewrite.
DVDs can be single sided (SS DVD) or dual sided (DS DVD). Additionally, the format on each side can be single layer (SL) or dual-layer (DL). With the DL format, there are two pitted layers on each data side, and each layer has a different reflectivity index. A DS DVD DL can have capacity of 17.08 GB of data.
