XCP and Xenserver store their Virtual Disk Images on storage repository. To see how much space you have on your LVM or lvmoisci storage repositories from the commandline can be quite a chore so I wrote a df command for storage repositories. My dfsr command mimics the output of the Linux df command with the human readable flag set (-h). All values will be printed in Kilobytes, Megabytes, Gigabytes and so on. It shows the size of the repository, how much is used, how much is available, the percent used and the Storage Repository type.
Get it from my Virtualization downloads section.