Hi, my environment info: centos-release.x86_64 7-7.1908.0.el7.centos glusterfs.x86_64 6.8-1.el7 ovirt-engine.noarch 4.3.9.4-1.el7 ovirt-release43.noarch 4.3.9-1.el7 I have an external agent (openstack staging_oviirt) that powers on/off VMs during bulk install. See also here some other details: https://lists.ovirt.org/archives/list/users@ovirt.org/thread/B4CDWTAR7YLRLRS... I repeat many times the installation for test purposes and during these phases the application powers on (through ostacpm user) about 8 VMs in the same moment. Sometimes it happens that one or more of them fail to start and in web admin gui I see this kind of sequence of events: VM ostack-ceph2 was started by ostackpm@internal-authz (Host: ovirt.mydomain). User <UNKNOWN> got disconnected from VM ostack-ceph2. VM ostack-ceph2 is down with error. Exit message: Unable to add bridge vlan23 port vnet21: Device or resource busy. Failed to run VM ostack-ceph2 on Host ovirt.mydomain Failed to run VM ostack-ceph2 (User: ostackpm@internal-authz). Soon I press the start button from web admin gui and the VM powers on without problems. I think this kind of problem doesn't depend on the rest api agent. Could it be a sort of bug or concurrency of power on commands? If I grep VM UUID and name of the VM for the one above, I get this in engine.log: https://drive.google.com/file/d/1QsedDqvlbvVPCifDNted4ipSsJ2GeBJV/view?usp=s... On ovirt host I see: 2020-05-04 10:16:05,491+0200 ERROR (vm/38f806e7) [virt.vm] (vmId='38f806e7-5c48-4ffe-90e8-671b1a585256') The vm start process failed (vm:934) Traceback (most recent call last): File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 868, in _startUnderlyingVm self._run() File "/usr/lib/python2.7/site-packages/vdsm/virt/vm.py", line 2895, in _run dom.createWithFlags(flags) File "/usr/lib/python2.7/site-packages/vdsm/common/libvirtconnection.py", line 131, in wrapper ret = f(*args, **kwargs) File "/usr/lib/python2.7/site-packages/vdsm/common/function.py", line 94, in wrapper return func(inst, *args, **kwargs) File "/usr/lib64/python2.7/site-packages/libvirt.py", line 1110, in createWithFlags if ret == -1: raise libvirtError ('virDomainCreateWithFlags() failed', dom=self) libvirtError: Unable to add bridge vlan23 port vnet21: Device or resource busy 2020-05-04 10:16:05,492+0200 INFO (vm/38f806e7) [virt.vm] (vmId='38f806e7-5c48-4ffe-90e8-671b1a585256') Changed state to Down: Unable to add bridge vlan23 port vnet21: Device or resource busy (code=1) (vm:1702) Let me know if you meed more information Gianluca