For rewriteable CD-RW, DVD-RW, DVD+RW, DVD-RAM, or BD-RE media, the laser is acclimated to melt a crystalline metal alloy in the recording layer of the disc. Depending on the chunk of gift applied, the gob may be allowed to melt hind (change the phase back) into crystalline form or left in an amorphous form, enabling marks of varying reflectivity to be created.

On the other hand, optical drives were developed with an assumption of achieving a constant throughput, in CD drives initially equal to 150 KiB/s. It was a hallmark important for streaming audio data, that always tend to claim a immutable dot rate. But to ensure no disc capacity is wasted, a head site had to transfer data at a maximum linear amount at all times too, without slowing on the outer rim of disc.