Could ring cache really improve performance in Cassandra?

Hi, I'm doing stress test on Cassandra. And I learn that using ring cache can improve the performance because the client requests can directly go to the target Cassandra server and the coordinator Cassandra node is the desired target node. In this way, there is no need for coordinator node to

Cassandra Doesn't Get Linear Performance Increment in Stress Test on Amazon EC2

Hi, I am doing stress test on Datastax Cassandra Community 2.1.2, not using the provided stress test tool, but use my own stress-test client code instead(I write some C++ stress test code). My Cassandra cluster is deployed on Amazon EC2, using the provided Datastax Community AMI( HVM instances )