For example, I have now a project that works in production and I want to migrate from standalone to Replica Set. The database is already quite large. What is the correct: should I first set up a Replica Set with empty databases - and then use mongodump to transfer data? Or should I first, when tuning the Replica Set on each node, create a database with the same data and then initialize the Replica Set?
Or I want to change the topology of the existing Replica Set and add one or several nodes? How can I transfer data to new nodes? Is it necessary to stop all nodes for this?