The default timeout about vCenter server(5.5 used) is 30 minutes, so when session is timeout and then concurrent create two volumes through cinder API. There will be one of volumes creation failed. The error log is here: http://paste.openstack.org/show/246678/ Looks like if there is concurrent requests, the vmware driver will re-create the session both at same time. I'm not sure whether it is the issue point. Need some help from VMware engineer, thanks. -- Best Wishes For You! -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.openstack.org/pipermail/openstack-dev/attachments/20150530/1dbd69ad/attachment.html>