Using multiple libraries

If you copy all your images from iphoto to Aperture does that mean you have 2 libraries on your hard drive? And therefore using twice the storage space?

Also, is there a way to combine libraries because when I look at my iphoto library from Aperture my photo stream does not appear, ( this is a separate library).

Ideally I would like to see photo stream from my iphone and my iphoto library at the same time in Aperture. I am using Aperture 3.3.2. Lion and iphoto 11.

Thank you in advance for any help.