This was found in queens but is likely in later levels as well of the VMAX FC driver.
During our testing, sometimes this failure would occur during a volume terminate connection.
It seems like the driver logic needs to be changed so that this condition is a success, not a failure, because the volume is already the proper storage group. Here is a partial logging sequence:
2018-11-15 13:00:29.248 1715 INFO cinder.volume.drivers.dell_emc.vmax.common [req-1abeab15-7d1a-4fe2-a3fa-991ccd87c41e 0688b01e6439ca32d698d20789d52169126fb41fb1a4ddafcebb97d854e836c9 fa38e290709948f5876995c490a91690 - default default] Terminate connection: volume-vm-vsnp-28a4aac8-00000001-boot-0-607cbc4f-1196.
2018-11-15 13:00:32.426 1715 INFO cinder.volume.drivers.dell_emc.vmax.masking [req-1abeab15-7d1a-4fe2-a3fa-991ccd87c41e 0688b01e6439ca32d698d20789d52169126fb41fb1a4ddafcebb97d854e836c9 fa38e290709948f5876995c490a91690 - default default] Masking view OS-828422A_78562FX_1-F-PVC_PG-MV successfully deleted.
2018-11-15 13:00:32.449 1715 INFO cinder.volume.drivers.dell_emc.vmax.masking [req-1abeab15-7d1a-4fe2-a3fa-991ccd87c41e 0688b01e6439ca32d698d20789d52169126fb41fb1a4ddafcebb97d854e836c9 fa38e290709948f5876995c490a91690 - default default] Using existing default storage group
...
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/masking.py", line 1171, in do_remove_volume_from_sg
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils extra_specs, move, connector)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/masking.py", line 1219, in _last_vol_in_sg
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils device_id, volume_name, extra_specs, connector, move)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/masking.py", line 1286, in _last_vol_masking_views
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils parent_sg_name, connector, move, extra_specs)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/masking.py", line 1404, in _delete_mv_ig_and_sg
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils extra_specs, device_id, move)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/masking.py", line 1369, in _delete_cascaded_storage_groups
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils extra_specs, src_sg=child_sg_name)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/masking.py", line 1447, in add_volume_to_default_storage_group
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils _move_vol_to_default_sg(storagegroup_name)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "<string>", line 2, in _move_vol_to_default_sg
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/coordination.py", line 151, in _synchronized
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils return f(*a, **k)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/masking.py", line 1446, in _move_vol_to_default_sg
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils default_sg_name, extra_specs, force=True)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/rest.py", line 972, in move_volume_between_storage_groups
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils array, source_storagegroup_name, payload)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/rest.py", line 674, in modify_storage_group
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils resource_name=storagegroup)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/rest.py", line 377, in modify_resource
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils self.check_status_code_success(operation, status_code, message)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils File "/usr/lib/python2.7/site-packages/cinder/volume/drivers/dell_emc/vmax/rest.py", line 251, in check_status_code_success
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils data=exception_message)
2018-11-15 13:00:32.473 1715 ERROR powervc_cinder.zonemanager.powervc_utils VolumeBackendAPIException: Bad or unexpected response from the storage volume backend API: Error modify storagegroup resource. The status code received is 500 and the message is {u'message': u'A problem occurred modifying the storage group resource: Storage Group [OS-no_SLO-SG] already contains the following volumes : [00063]'}.
