Comment 0 for bug 1603282

The VDisk-to-host mapping may be fail due to the SCSI LUN id is already uesed by other VDisk mapping to this host with this SCSI LUN id, which is caused by two cinder volume nodes run parallelly.

In the storwize volume driver for a volume attaching shouldn't try to calculate SCSI LUN ID locally during initialize_connection() since two cinder volume nodes may run parallelly. The SCSI LUN ID maybe duplicate during serveral cinder volume nodes run parallelly. The storwize backend can decide SCSI LUN ID.

See the error message:
2016-06-09 15:42:06.135 15042 DEBUG oslo_concurrency.processutils [req-cda98724-4f9d-4c46-b88a-f5d3a841cfaa - - - - -] Result was 1 ssh_execute /usr/lib/python2.7/site-packages/oslo_concurrency/processutils.py:330
2016-06-09 15:42:06.136 15042 ERROR cinder.volume.drivers.san.san [req-cda98724-4f9d-4c46-b88a-f5d3a841cfaa - - - - -] Unexpected error while running command.
Command: svctask mkvdiskhostmap
Exit code: 1
Stdout: u''
Stderr: u'CMMVC5879E The VDisk-to-host mapping was not created because a VDisk is already mapped to this host with this SCSI LUN.\n'