To create an additional storage in OpenStack, follow the below given steps.
Configure the OpenStack Compute and the OpenStack Block Storage services throug /etc/cinder/cinder.conf file.
Use the openstack volume create command to create a volume. This command creates an LVM into the volume group (VG) cinder-volumes.
Use the openstack server add volume command to attach the volume to an instance. This command creates a unique IQN that is exposed to the compute node.
The compute node, which runs the instance, now has an active iSCSI session and new local storage (usually a /dev/sdX disk).
Libvirt uses that local storage as storage for the instance. The instance gets a new disk (usually a /dev/vdX disk).
Hope this will help You.