http://www.computerforums.org/forums/server-articles/how-setup-live-xenservers-backups-208663.html

mkdir /home/backup
mkdir /VM_Backup

# Use a command like this if you want to send backups to a CIFS share
#mount -t cifs "//192.168.0.20/VM_Backup" -o username=username,password=password /VM_Backup

cd /VM_Backup
wget http://www.andy-burton.co.uk/files/xenserver_backup/xenserver_backup.tar.gz
tar -xzf xenserver_backup.tar.gz
chmod 777 v*
cd /home/backup

This file is used to easily start the live backups of your XenServer VMs:

vi vmbackups.sh

#!/bin/bash
set -x

umount -f /VM_Backup

mount -t cifs "//192.168.0.20/VM_Backup" -o username=username,password=password /VM_Backup

/VM_Backup/CLEARDOWN.sh

/VM_Backup/vm_backup.sh

/VM_Backups/CLEARDOWN.sh

sleep 120

/VM_Backups/CLEARDOWN.sh