Cassandra JMeter plugin supports all the jmeter functions and variables, hence making it a right fit to generate data into cassandra. You can also validate the data and measure performance/throuhput of a cassandra cluster.
INSTALLATION:
https://github.com/Netflix/CassJMeter/wiki/Installation-Instruction
DETAILS:
https://github.com/Netflix/CassJMeter & https://github.com/Netflix/CassJMeter/wiki