I am developing an automated script for our server maintenance. It would execute a nodetool repair ever weekend. We have 3 nodes in DC1 and 3 in DC2. We are currently on Cassandra 0.8.4.
I am trying to understand effects of what would happens if connectivity between DC1 and DC2 is lost or couple of replica goes down BEFORE or DURING a nodetool repair. It could be a network issue, an network upgrade(which usually happens on weekends),or something else. I understand that nodetool repair computes a Merkle tree for each range of data on that node, and compares it with the versions on other replicas. So if their is no connectivity between replicas how would a nodetool repair behave ? Will it really repair the nodes. Do i have to rerun node tool repair after all nodes are up and connectivity is restored. Will their be any side effects of this event which i need to handle ? I goggled about it but couldn't find much details. Any insight would be helpful. Thanks, - Sachin
