This is in the engine.log

[storage.StoragePool] Trying to upgrade master domain `f9aaa65a-0ac7-4c61-a27d-15af3901
6419` (sp:479)
2019-07-06 00:24:14,056+0800 INFO  (tasks/5) [storage.StorageDomain] Converting domain f9aaa65a-0ac7-4c61-a27d-15af39016419 volumes
metadata from version 4 to version 5 (fileSD:811)
2019-07-06 00:24:14,121+0800 INFO  (tasks/5) [storage.StorageDomain] Removing remnants of deleted images [] (fileSD:740)
2019-07-06 00:24:14,121+0800 ERROR (tasks/5) [storage.StoragePool] Unexpected error (sp:383)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/storage/sp.py", line 333, in startSpm