What is optical disk & why removed it? || use of optical disk

optical disk is used for externally insert storage . optical disk which is more commonly used in storage device. And optical disk has very high storage density and data integrated .

It is relatively inexpensive and has a long life at least 20 year. It is several millimeters away from the disk surface .hence there are no disk wear and no faces problem of head crash .so now a time remove a optical disk by a computers .

the drawback of an optical disk system is the longer access time compared to hard disk .the type of optical disk are :