[ovirt-users] Upgrade from CentOS 6.8 (oVirt 3.5) to CentOS 7 (oVirt 4.0)

I would upgrade my CentOS 6.8 to 7 on my cluster of 5 ovirt nodes (actually I'm running oVirt 3.5 and glusterfs 3.7).  Anyone has experienced troubles for this upgrade? Thank you, Fedele