Ok, how do I get a data stream on a marble (lasers?) and how dense can I make it - or how big can I make a marble? Bonus points if I can simply make a glass CD

Ok, how do I get a data stream on a marble (lasers?) and how dense can I make it - or how big can I make a marble? Bonus points if I can simply make a glass CD, DVD, Blu-Ray, etc.