Hi, I am using libvirt version 0.10.1 and qemu-kvm version 1.2.0 with RHEL 6.3 When I use libvirt API to make block migrate with a VM, it failed frequently. I check the migrated VM and found that the filesystem damaged. But sometimes it works very fine, I don't know why, it seems to be random. All failed tests have the same condition, image transfer incompletely in live migration. The image I used is 10GB size, after a failed migration it has only about 400MB to 3GB in remote host. Here is the code: import libvirt from xml.dom import minidom name = "vm-01" host = libvirt.open("qemu:///system") vm = host.lookupByNmae(name) vm_xml_file = "/etc/libvirt/qemu/%s.xml" % name vm_xml = minidom.parse(vm_xml_file).documentElement.toxml() remote_host = "qemu+ssh://host02/system" remote = libvirt.open(remote_host) try: vm.migrate2(remote, vm_xml, 89, name, None, 0) except Exception,e: print str(e) Before run the code I have already create a image for migration in remote host 'host02'. Path, size, and privilege all OK. Here is the related log: in source host 'host01': 2012-11-24 05:14:40.001+0000: 24888: warning : qemuDomainObjBeginJobInternal:838 : Cannot start job (query, none) for domain wrksp-776; current job is (async nested, migration out) owned by (24890, 24890) 2012-11-24 05:16:16.398+0000: 24888: error : qemuDomainObjBeginJobInternal:842 : Timed out during operation: cannot acquire state change lock 2012-11-24 05:16:21.317+0000: 24887: error : virNetSocketReadWire:1184 : End of file while reading data: Input/output error in remote host 'host02': 2012-11-24 05:14:00.776+0000: 11065: warning : qemuDomainObjEnterMonitorInternal:993 : This thread seems to be the async job owner; entering monitor without asking for a nested job is dangerous 2012-11-24 05:14:01.196+0000: 11065: warning : qemuDomainObjEnterMonitorInternal:993 : This thread seems to be the async job owner; entering monitor without asking for a nested job is dangerous 2012-11-24 05:14:01.198+0000: 11065: warning : qemuDomainObjEnterMonitorInternal:993 : This thread seems to be the async job owner; entering monitor without asking for a nested job is dangerous 2012-11-24 05:14:01.208+0000: 11065: warning : qemuDomainObjEnterMonitorInternal:993 : This thread seems to be the async job owner; entering monitor without asking for a nested job is dangerous 2012-11-24 05:14:01.211+0000: 11065: warning : qemuDomainObjEnterMonitorInternal:993 : This thread seems to be the async job owner; entering monitor without asking for a nested job is dangerous I try to use command "virsh migrate vm-01 --live --copy-storage-all --persistent --undefinesource qemu+ssh://host02/system --verbose", the test results have no change, common but not regular. Even after my once successful test, it will certainly fail when I try to make a second migrate with the same VM. How can I solve this problem？ Anything is helpful. Thanks.