Hi,
i published my backup solution for VMs running on a Citrix XenServer Host or Pool at GitHub.
https://github.com/avarrish/xenbackup
It creates snapshots of all VMs running and download it to your backup location.
You need the Python XenAPI which is available here:
https://pypi.python.org/pypi/XenAPI
http://xenserver.org/overview-xenserver-open-source-virtualization/download.html (SDK)
If you want to monitor your backups take a look at the nagios script.
