In a multi-threaded environment where multiple threads are trying to get list of all VMs on host, we have seen that at times this list is missing couple of VMs. The code used is fairly simple, it makes three libvirt calls. 1. Call virConnectNumOfDefinedDomains() to get number of defined domains. 2. Call virConnectNumOfDomains() to get a list of active domains. 3. If there are defined domains, then call virConnectListDefinedDomains (conn, (char **)names, n_names), where n_names is the count returned from #1. The count returned from #3 is less than the one returned from #1. I have bumped up the connection count in libvirtd.conf to 100, and using 20 threads. On average I get one missing defined VM every 5 runs of this test. I have 25 running VMs and 8 defined VMs on this host. # rpm -aq | grep libvirt libvirt-python-0.8.7-18.el6_1.1.x86_64 libvirt-0.8.7-18.el6_1.1.x86_64 libvirt-cim-0.5.14-1.el6.x86_64 libvirt-client-0.8.7-18.el6_1.1.x86_64 Its RHEL 6.1 running 2.6.32-131.17.1.el6.x86_64 Regards, Sharad Mishra