[ovirt-users] HELP Upgrade hypervisors from CentOS 6.8 to CentOS 7

Hi, I'd like to upgrade my oVirt environment from 3.5 to 3.6 and maybe 4, actually the manager oVirt is un 3.5 version, installed on a CentOS 7.2 and the two hypervisors are installed on CentOS 6.8. I need anyway to upgrade the hosts to be able to move to 3.6. I've tried to upgrade the first host, but I had of course issues telling that it can't be possible to mix different OS in the same cluster, I've also tried to create another cluster to put this host without success. What is the best way to upgrade cleanly and safely ? Thank you in advance for your advices Alain VONDRA Chargé d'exploitation des Systèmes d'Information Direction Administrative et Financière +33 1 44 39 77 76 UNICEF France 3 rue Duguay Trouin 75006 PARIS www.unicef.fr