cluster

Please see my comments in line below beginning with "<<<"

in every node of vcs the in-memory contain the information loaded from main.cf and the information related to what service is up on what node.right?

<<< only the first node (where had is up first) gets initial cluster configuration from the on disk main.cf,  cluser resources states and cluster configuration can change from time to time online.  GAB is responsible for keeping up this info on each node's had running in kernel updated

when a service is brought up on a node then this information from memory is copied to the other nodes.right?

<<< correct (do not norammly use the word copy).  this is what GAB prot h for - communicates the status of resources running on each system to all systems in the cluster.