Fedora xen - May 2006 - Question on disk usage and allocation per guest

Our guest images are stored in /home and an ls -al lists their allocated
sizes correctly.

However a du -sh on the image only lists the actual usage within the image.
And a df -h only shows actual disk usage for the entire server.

How do we get a list of the allocated disk space?

I assume that similar to memory, you cannot over-allocate disk space with
Xen guests?

Thanks