Does Unionfs allow exceeding the limits of the CD of ~700MB?

If applied to a DVD of Knoppix, will the Unionfs extend the usefulness of the DVD format from the present limit of 2.1GB on disc to the full 4.4GB of storage capacity by allowing the loading thru Unionfs of an additional 2.3GB of compressed files(assuming all of Unionfs is compressed, or is it?).?? If it isn't compressed, can it be?

Correct answers to these queries should be helpful to all users, stupid questions or no.