Description of problem:

It is a common task to configure multiple cinder NetApp backends that use the same driver and same netapp_storage_protocol. For example, to configure multiple cinder backends that use NFS driver.

It is currently impossible to do so with standard tripleo templates [1]:

~~~
Deploying multiple instances of a NetApp back end requires a custom back end configuration. See the Custom Block Storage Back End Deployment Guide for instructions. 
~~~

Custom Block Storage Back End Deployment Guide [2] is basically recommend you to provide custome hieradata for cinder puppets, but this approach is not perfect. For example, it is impossible to use it to properly configure multiple NFS-based backends: NFS shares are configured in separate configuration file, usually named "/etc/cinder/shares.conf". But what if you need multiple backend and multiple files? The simplest way to properly create them inside cinder-volume container is to customize container image and this is certainly an overkill for such a simple task.

It is also possible that other backends have such limitations and a general change could be used to provide a valuable feature in next releases.

[1] https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/13/html/netapp_block_storage_back_end_guide/edityaml
[2] https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/13/html-single/custom_block_storage_back_end_deployment_guide/