Hi, I'm in the process of upgrading to 4.1 from 3.6.7 (centos 6) The default cluster runs in 3.5 compatibility mode. I cannot add a new Centos 7 host: 2017-10-23 13:50:08,359 ERROR [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (DefaultQuartzScheduler_Worker-40) [6a0dd9df] Correlation ID: 6a0dd9df, Job ID: e570c94b-bbd8-486b-bb93-3d28fb905bb3, Call Stack: null, Custom Event ID: -1, Message: Host v5 is compatible with versions (3.6,4.0,4.1) and cannot join Cluster Default which is set to version 3.5. I'm following https://www.ovirt.org/feature/inclusterupgrade/ for upgrading. I've set engine-config -s CheckMixedRhelVersions=false --cver=3.5 restarted and set Scheduling policy InClusterUpgrade Any recommendations how to proceed without shutting down all VMs? I also want to avoid creating a new cluster with 3.6 version cause then I will have to shutdown all VMs again. Thanks G ps. The steps I had in mind were: upgrade serially hosts to Centos 7 migrate VMs there backup-restore engine to new Centos 7 machine