If you have an issue booting your xen 5 because you have loose MBR information, here is how you can restore it very quickly.
Proceed booting your server with a live cd distribution, like wifiSlax, and run the next commands.
mount the necessary partitions in your harddisk to have / and /boot mounted.
Let's say you have sda1 assigned to boot and sda2 to root partition.
# mount /dev/sda2 /mnt
# mount /dev/sda1 /mnt/boot
or like in my case, mount your RAID1 partitions to access to yor root Read more...