Storing libraries on external devices

Hi everybody..

In these last weeks my library always grown and now is giving me HD space problem, so that I must find some way to store elsewhere most of my digital collection.
So, I'm asking if is possible to store the Calibre libraries on external devices: I can easily imagine how to do that with external hard-disk (but it's only a maybe, I never tryed it and I don't know if it could work) but I wonder if it coud be possible to do such a thing on DVD, for example.. of course accepting the assumption to never edit books metadata..

Actually I really don't know which could be the better solution.. ideas, please?

Thank you very much for payng attention,
see you soon! ;)