When trying to add a second local storage data store to a Hypervisor I am getting the error "Has already been taken."
Add the local storage data store without selecting a Hypervisor for it. This will cause it to be treated like a normal data store. Then enter your MySQL Database and enter:
update data_stores set local_hypervisor_id='x' where id='x';
(Make sure you have the id for each. This can be obtained via the URL in the OnApp UI, or via database query.) Now the data store is attached to the Hypervisor as a second local storage data store.
The OnApp UI limits the amount of local storage data stores to one per Hypervisor.