+ You can send update queries to any database server.
+ If one Master failed, the other one will be ready to take over.
- You may have data corruption and/or index conflicts if not setup properly.
- You may get inconsistent/incomplete data when one node fails to get updates from the other one. Remember, you will be reading/writing to both servers.
+ No possibility for index conflict. Update is done on one node only.
+ Always, you can get consistent data from the Master and from up-to-date Slave node(s). This can be achieved as far as the application updating the database is behaving as expected!!
- You can send update queries only to the Master node.
- You may need to manually failover to one of the Slave nodes when the Master node fails.
Just a reminder
Doing database replication does not mean that you are doing database backup. The database backup is important to be able to restore a consistent copy of your data when a corruption occurs. In this case, all your replication nodes may have the same corrupted data!!