In Britain or the USA, pieces would be omitted, because CD is a count noun. But use of pieces for countable things seems to be the norm in this part of the world. Here is a sign in a supermarket:
Again, we find pieces used to refer to something countable, apples. I strongly suspect that this usage will become the norm in World Englishes. After all, it is perfectly clear, so everyone can understand it with no problem.
