Description of problem:
One of the host in the cluster seems not able to run vms or to hotplug with ISCSI disks. The other host in the cluster *works fine*, I've checked the packages and there's doesn't seem to be an issue with it. Also the host works as SPM for typical operations, migration of disks, adding domains, ...

Packages are the proper ones for the release. Wonder if you guys can take a look.


Version-Release number of selected component (if applicable):
rhevm-3.6.1.3-0.1.el6.noarch
libvirt-daemon-kvm-1.2.17-13.el7_2.2.ppc64le
libvirt-docs-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-driver-lxc-1.2.17-13.el7_2.2.ppc64le
libvirt-lock-sanlock-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-driver-nodedev-1.2.17-13.el7_2.2.ppc64le
libvirt-python-1.2.17-2.el7.ppc64le
libvirt-daemon-driver-qemu-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-driver-nwfilter-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-driver-interface-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-config-network-1.2.17-13.el7_2.2.ppc64le
libvirt-debuginfo-1.2.17-13.el7_2.2.ppc64le
libvirt-client-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-driver-storage-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-driver-secret-1.2.17-13.el7_2.2.ppc64le
libvirt-devel-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-driver-network-1.2.17-13.el7_2.2.ppc64le
libvirt-daemon-config-nwfilter-1.2.17-13.el7_2.2.ppc64le
libvirt-login-shell-1.2.17-13.el7_2.2.ppc64le
qemu-img-rhev-2.3.0-31.el7_2.4.ppc64le
ipxe-roms-qemu-20130517-7.gitc4bce43.el7.noarch
libvirt-daemon-driver-qemu-1.2.17-13.el7_2.2.ppc64le
qemu-kvm-tools-rhev-2.3.0-31.el7_2.4.ppc64le
qemu-kvm-rhev-2.3.0-31.el7_2.4.ppc64le
qemu-kvm-common-rhev-2.3.0-31.el7_2.4.ppc64le
vdsm-jsonrpc-4.17.13-1.el7ev.noarch
vdsm-xmlrpc-4.17.13-1.el7ev.noarch
vdsm-python-4.17.13-1.el7ev.noarch
vdsm-4.17.13-1.el7ev.noarch
vdsm-infra-4.17.13-1.el7ev.noarch
vdsm-yajsonrpc-4.17.13-1.el7ev.noarch
vdsm-cli-4.17.13-1.el7ev.noarch


How reproducible:
100%

Steps to Reproduce:
1. Create a vm with a boot disk on the iscsi domain (or use an already created one)
2. Try to start the vm

Actual results:
Thread-23957::ERROR::2016-01-12 05:34:03,418::vm::758::virt.vm::(_startUnderlyingVm) vmId=`ccfc6e2b-60dc-4b29-a10f-ddc6d00b1c99`::The vm start process failed
Traceback (most recent call last):
  File "/usr/share/vdsm/virt/vm.py", line 702, in _startUnderlyingVm
    self._run()
  File "/usr/share/vdsm/virt/vm.py", line 1889, in _run
    self._connection.createXML(domxml, flags),
  File "/usr/lib/python2.7/site-packages/vdsm/libvirtconnection.py", line 124, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 3611, in createXML
    if ret is None:raise libvirtError('virDomainCreateXML() failed', conn=self)
libvirtError: internal error: process exited while connecting to monitor: 2016-01-12T10:34:03.210899Z qemu-kvm: -drive file=/rhev/data-center/b3115183-d522-428b-9dce-2809fe39a79d/bc7ac735-26d4-4bbd-a45b-0ac909896d00/images/9b158596-e5fe-40d5-95ce-da802a07756a/1ec33a65-7728-4259-a36b-9c1508907e35,if=none,id=drive-virtio-disk1,format=qcow2,serial=9b158596-e5fe-40d5-95ce-da802a07756a,cache=none,werror=stop,rerror=stop,aio=native: Could not open '/rhev/data-center/b3115183-d522-428b-9dce-2809fe39a79d/bc7ac735-26d4-4bbd-a45b-0ac909896d00/images/9b158596-e5fe-40d5-95ce-da802a07756a/1ec33a65-7728-4259-a36b-9c1508907e35': Permission denied

Also regarding the hotplug:
Steps to Reproduce:
1. Use a vm with a boot disk on an nfs domain and start it
2. Hotplug a iscsi disk (in VMs -> Disks -> New)

Actual results:
Disk is added but fails to hotplug with:
[org.ovirt.engine.core.vdsbroker.vdsbroker.HotPlugDiskVDSCommand] (ajp-/127.0.0.1:8702-2) [5ab6ea5f] Failed in 'HotPlugDiskVDS' method
2016-01-10 02:37:01,532 ERROR [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (ajp-/127.0.0.1:8702-2) [5ab6ea5f] Correlation ID: null, Call Stack: null, Custom Event ID: -1, Message: VDSM host_mixed_1 command failed: internal error: unable to execute QEMU command '__com.redhat_drive_add': Device 'drive-virtio-disk0' could not be initialized


Additional info:
- The host doesn't seem to have any issue with nfs or to handle iscsi domains (add them/remove, create disks/migrate, ...)
- Other host in the cluster doesn't have any issue like this one