What is the best strategy for configuring a SQL cluster?

Hi,

I need four instances of sql, where one of the servers is down, the other is able to take over all the connections.

I thought about the following scenarios:

1 - A single cluster with all four instances installed on all nodes. In all, there would be four servants. So any of the nodes could handle any of the four instances.

2 - Two cluster, each with two instances and two servers;

3 - A single cluster with four nodes. Since two servers would have two instances and the other two would have two other instances.

NOTE: I need a volume for individual backup per instance or a shared between all the instants.

What kind of RAID is LUN for data, log and tempdb?

Thank you.