1. Best practice is don't. But if you must, you need to install another instance. 2. Min/max memory for each SQL instance; ensure you have adequate hardware for both instances to run on one node in case you lose the other node 3. You'll want to fix whatever issue occurred and failback to balance the cluster again.
1- Do I need to install sqlserver again on the newly active node? Or just add new App to this Node? 2- Each server has 32GB RAM? what do u mean min/max setting? 3- What change should be done in Windows Cluster Admin?
1. It's just another install, same as you did the first time. 2. Well you need to set these in case of a failover. Min/max memory in sp_configure for each instance. 3. It depends why the failover occurred. There are probably hundreds of reasons.
1. You need to install a new Failover Cluster Instance, and add a node. 2. There are 2 routs you can go, you can set each instance's Max Server Memory to something like 14GB so in the case when they are both running on the same node, there is enough memory. You could also set them both to somethng like 24GB. Obviously there is not enough memory on a single node to be able to give each instance 24GB if there is a failover and they are both running on a single node, but there would be enough for both instances to start and run. This would be ok if you have good monitoring, and can get in and quickly reconfigure memory in the case of a failover. 3. No changes required in Windows Cluster Admin. You will need another set of Shared storage for the 2nd instance though.