I want to create my own private Eos chain for my own specific use case which is very RAM hungry. Imagine that I have a network of nodes having, for example, 32GB of ram. But I have two contracts with very long arrays, each having 20GB. Are both contracts in the memory so nodes needs to have 2*20GB of memory? Or how this works? Thanks, T
Each node has a complete copy of the RAM of the blockchain. You need enough RAM on all nodes to keep the data there.
If you're starting a private chain, you don't need 21 nodes. Your chain can have less nodes.
Are you sure you need all this data in RAM? Have you looked into demux? This might allow you to keep parts of the data in a regular database while still being recorded on chain.