Documentation about deciding no. of cluster nodes, CPU, RAM, disks and high availability etc... is needed.
How you size your cluster will depend on the use case and what requirements you have around performance and load so it would help if you could provide some details around this. As an introduction I would recommend you have a look at the following resources. Even if some of them refer to the cloud most of the guidance also applies to on-premise deployments.
Thank you, Chris!
Let me check the links!