SCv3020 vCenter

Hi, Could someone give me some advice. I have an SCv3020 connected to two R640 ESXi servers.

I need to allow volumes access on both servers and I should make these two servers a cluster for vCenter. I can make a cluster with the "Create Server Cluster" function and move the servers under it. I have production servers on both servers.

Does anyone know, can I move the servers under the Server Cluster during use or should the production servers be shut down during the move? Is there any other things I should consider before moving servers?