Setting up a multiple-instance cluster with two nodes

You cannot do shared database access in a cluster. It is simply not possible. There is only one copy of your database, and it will reside on the node where you place it or it gets placed due to a failover. When a node fails, the databases are transferred to the other node and restarted, but they are precisely the same databases regardless of which node has ownership. During failover, yes, both SQL Server instances can run on a single node which is what clustering was designed for. If you want to take advantage of the processing capacity on both servers, you can configure one SQL Server instance to run on Node A and a different SQL Server instance to run on Node B. Keeping in mind that during a failover when both SQL Server instances are running on the same node, you can get degradation in performance.

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