Hi, we have a master node in site-1 with 3 primary indexers in site-1 and 3 indexers in site 2. What configuration changes are to be made if we need to configure a new master node in site-2 as the DR? Are both master's are to be running all the time or only one?
A cluster can have one and only one cluster master so both cluster masters (active and standby) will not be running all the time. Following documentation page provides details on steps and configuration changes that you would do in case of DR (migrating cluster to a new server).
https://docs.splunk.com/Documentation/Splunk/6.5.3/Indexer/Handlemasternodefailure