Not sure if it's related, but while adding the host, about a minute before the timeout\error occurs, /var/log/vdsm/mom.log shows: 2019-06-16 22:58:46,799 - mom - ERROR - Failed to initialize MOM threads Traceback (most recent call last): File "/usr/lib/python2.7/site-packages/mom/__init__.py", line 29, in run hypervisor_iface = self.get_hypervisor_interface() File "/usr/lib/python2.7/site-packages/mom/__init__.py", line 217, in get_hypervisor_interface return module.instance(self.config) File "/usr/lib/python2.7/site-packages/mom/HypervisorInterfaces/vdsmjsonrpcclientInterface.py", line 96, in instance return JsonRpcVdsmClientInterface() File "/usr/lib/python2.7/site-packages/mom/HypervisorInterfaces/vdsmjsonrpcclientInterface.py", line 31, in __init__ self._vdsm_api = client.connect(host="localhost") File "/usr/lib/python2.7/site-packages/vdsm/client.py", line 157, in connect raise ConnectionError(host, port, use_tls, timeout, e) ConnectionError: Connection to localhost:54321 with use_tls=True, timeout=60 failed: [Errno 111] Connection refused Is this the cause or is this benign? As for your suggestion for the engine-VM, for now I've switched to using plain CentOS instead of Node, and this shows the problem occurs prior to adding the engine-VM. The failure occurs in the stage before: adding a new host.