In Cassandra 1.2 and later, large numbers of schema changes can simultaneously take place in a cluster without any schema disagreement among nodes. For example, if one client sets a column to an integer and another client sets the column to text, one or the another action will be instantly agreed upon. Which action is agreed upon is unpredictable.
The new schema resolution design eliminates delays caused by schema changes when a new node joins the cluster. As soon as the node joins the cluster, it receives the current schema with instantaneous reconciliation of changes.
In the event that a schema disagreement occurs, check for and resolve schema disagreements as follows:
$ cassandra-cli -host localhost -port 9160 [default@unknown] DESCRIBE cluster;
[default@unknown] describe cluster; Cluster Information: Snitch: com.datastax.bdp.snitch.DseDelegateSnitch Partitioner: org.apache.cassandra.dht.RandomPartitioner Schema versions: UNREACHABLE: [10.202.205.203, 10.80.207.102, 10.116.138.23]