For a resource without any ‘colocation’ configuration, how the pacemaker to determine which node this resource will startup on?
Because on my system, when I stop a resource, then start it again, it always startup on node 2.
Even I migrate the resouce to node1, stop and start it again, then it also startup on node 2.
Pacemaker will, in the absence of (co-)location rules or utilization scores, allocate the resources in a round-robin manner for load-balancing; typically starting with the node with the lowest nodeid.
But since this is affected by groups etc, it is essentially random and not behaviour that should be relied on. If you need resources placed somewhere, use configuration rules that ensure that the node picked is functional for them.