Can a single Nova setup have multiple databases on different nodes?

From what I learned from the Nova documents, the database (MySQL, PostgreSQL, etc.) is setup along with the Cloud Controller. My question is: is it possible to configure multiple databases on different Nova nodes? If YES, how Nova keep the data consistency between these multiple databases?

I saw such description from the Nova Admin Guide (Diablo release, page 13 "System Achitecture"):
"To achieve the shared-nothing property with multiple copies of the same component, Nova keeps all the cloud system state in a distributed data store. Updates to system state are written into this store, using atomic transactions when required. Requests for system state are read out of this store. "

What does the "distributed data store" mean? it this "data store" referring to the database (MySQL, etc.)? If YES, could someone explain why it's distributed? If NOT, what does it mean?

Thanks a lot.