Hello, I have a newbie question regarding host/cluster compatibility versions. I hope someone could clarify this for me. We have an old lab setup in which we were managing KVM hostnodes using RHEV Manager (version 2.2.4.51796) . We are now trying to upgrade to the latest version of oVirt Engine (version 3.1.0_0001-1.8.el6). Now, when I add the old KVM node to oVirt Engine, I am getting following error message: Host's Compatibility Version doesn't match the Cluster's Compatibility Version Can someone tell me if oVirt Engine is backward-compatible with older hostnodes? Or do I need to upgrade one or more components (such as VDSM) on the hostnode to be compatible with new engine? Here is the version information from the hostnode I'm trying to add: OS : RHEV Hypervisor - 5.6 - 9.3.el5_6 Kernel : 2.6.18 - 238.5.1.el5 KVM : 83 - 224.el5 VDSM : 2.2.63.23 SPICE : 0.3.0 - 54.el5_5.2 Thanks, Ashok