RabbitMQ can send one message to different queues through exchange. While queueA and queueB on different node accept same message, will these two nodes store the message respectively on their own disk or using a common database to store this message once for sharing between nodes?
RabbitMQ in cluster does not share the same database-messages.
Each node has its own local database.
If want to learn more about that, I suggest to read: https://github.com/rabbitmq/internals/blob/master/queues_and_message_store.md