Hi Leena, First thing you should be concerned about is : Why the repair -pr operation doesnt complete ? Second comes the question : Which repair option is best?
One probable cause of stuck repairs is : if the firewall between DCs is closing TCP connections and Cassandra is trying to use such connections, repairs will hang. Please refer https://docs.datastax.com/en/cassandra/2.0/cassandra/troubleshooting/trblshootIdleFirewall.html . We faced that. Also make sure you comply with basic bandwidth requirement between DCs. Recommended is 1000 Mb/s (1 gigabit) or greater. Answers for specific questions: 1.As per my understanding, all replicas will not participate in dc local repairs and thus repair would be ineffective. You need to make sure that all replicas of a data in all dcs are in sync. 2. Every DC is not a ring. All DCs together form a token ring. So, I think yes you should run repair -pr on all nodes. 3. Yes. I dont have experience with incremental repairs. But you can run repair -pr on all nodes of all DCs. Regarding Best approach of repair, you should see some repair presentations of Cassandra Summit 2016. All are online now. I attended the summit and people using large clusters generally use sub range repairs to repair their clusters. But such large deployments are on older Cassandra versions and these deployments generally dont use vnodes. So people know easily which nodes hold which token range. Thanks Anuj
