Manuel, you just need to activate your cluster on startup as the error message suggests. In addition to the Ignite.active(true) API, there is an option to use a script: "$IGNITE_HOME/bin/control.sh --activate".
Whether you need persistence is for you to decide. For me persistence is needed if: - The data are too big to fit in memory. - You want your data to survive entire cluster going down (not just some nodes, which is addressed by configuring backups). - You do not want to spend time for initial data load. - You have legal requirements to persist data (like bank transactions info) For me typical web session data do not require persistence since they should fit in memory, you can configure backups for fault tolerance and there are no legal requirements to persist web data. Maybe you have some specific scenario.
