At this point, your cluster is up and running. There is data coming in and everything seems to be humming along. But Cassandra is not a set it and forget it system. There is maintenance required, and there are tools to help you perform the necessary maintenance tasks.
The most basic command that you should be familiar with when administering a Cassandra cluster is
nodetool is a command line interface to Cassandra cluster management. It can provide you with basic information about an individual node or all nodes in the cluster or ring.
As of Cassandra 1.2,
nodetool provides the options shown in Listing 7.1
usage: java org.apache.cassandra.tools.NodeCmd --host <arg> ...