how does ES store in a cluster with 5 nodes? All data on 5 nodes or how is that distributed?
I assume you mean Elasticsearch when you say "XXX".
Generally speaking, yes it will be spread across the nodes in the cluster. Ultimately it will depend on the number of shards for your index, and the number of indices.
OK. Do I have to manage this? Can I say: store it on 3 nodes instead off all?
You can store some data on some nodes, yes, look at allocation filtering. And yes, that is something you manage.
Without that Elasticsearch will handle it for you.