[ovirt-users] Upgrade datacenter from 3.6 to 4.0

[Arnaud Lauriou]

Hi,

What is the best way to upgrade a datacenter from ovirt 3.6 to 4.0 ?
Upgrade engine, hosts then cluster ?
If right, how do you upgrade a host running ovirt 3.6.7 ? Simple upgrade 
or fresh install ?
During the update process of a cluster, some hosts will be in 3.6.7 and 
others in 4.0.2, is it a problem for migrating VMs ?

Found docs about engine upgrade but not a lot about host and cluster.

Thanks,

Arnaud