Unfortunately, this is a separate engine running external to the oVirt cluster.

The main error on the hosts is: any idea what this Volume is referring to?

I have 3 existings storage domains

ISO EXPORT and DATA all upgraded to 4.3

None have this UUID.

VolumeDoesNotExist: Volume does not exist: (u'1d1b6dfd-197a-4583-8398-6b941dbca854',)

2019-07-05 23:02:15,954+0800 ERROR (tasks/0) [storage.StoragePool] failed: Volume does not exist: (u'1d1b6dfd-197a-4583-8398-6b941dbca854',) (sp:384)
2019-07-05 23:02:15,954+0800 INFO  (tasks/0) [storage.SANLock] Releasing Lease(name='SDM', path=u'/rhev/data-center/mnt/192.168.88.40:_genie_ovirt_data/f9aaa65a-0ac7-4c61-a27d-15af39016419/dom_md/leases', offset=1048576) (clusterlock:488)
2019-07-05 23:02:15,955+0800 INFO  (tasks/0) [storage.SANLock] Successfully released Lease(name='SDM', path=u'/rhev/data-center/mnt/192.168.88.40:_genie_ovirt_data/f9aaa65a-0ac7-4c61-a27d-15af39016419/dom_md/leases', offset=1048576) (clusterlock:497)
2019-07-05 23:02:15,955+0800 ERROR (tasks/0) [storage.TaskManager.Task] (Task='159b9026-7034-43c2-9587-8fec036e92ba') Unexpected error (task:875)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/storage/task.py", line 882, in _run
    return fn(*args, **kargs)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/task.py", line 336, in run
    return self.cmd(*self.argslist, **self.argsdict)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/sp.py", line 333, in startSpm
    self._upgradePool(expectedDomVersion, __securityOverride=True)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/securable.py", line 79, in wrapper
    return method(self, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/sp.py", line 484, in _upgradePool
    str(targetDomVersion))
  File "/usr/lib/python2.7/site-packages/vdsm/storage/sp.py", line 1108, in _convertDomain
    targetFormat)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/formatconverter.py", line 447, in convert
    converter(repoPath, hostId, imageRepo, isMsd)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/formatconverter.py", line 405, in v5DomainConverter
    domain.convert_volumes_metadata(target_version)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/fileSD.py", line 813, in convert_volumes_metadata
    for vol in self.iter_volumes():
  File "/usr/lib/python2.7/site-packages/vdsm/storage/sd.py", line 764, in iter_volumes
    yield self.produceVolume(img_id, vol_id)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/sd.py", line 846, in produceVolume
    volUUID)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/volume.py", line 817, in __init__
    self._manifest = self.manifestClass(repoPath, sdUUID, imgUUID, volUUID)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/fileVolume.py", line 71, in __init__
    volUUID)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/volume.py", line 86, in __init__
    self.validate()
  File "/usr/lib/python2.7/site-packages/vdsm/storage/volume.py", line 112, in validate
    self.validateVolumePath()
  File "/usr/lib/python2.7/site-packages/vdsm/storage/fileVolume.py", line 131, in validateVolumePath
    raise se.VolumeDoesNotExist(self.volUUID)