Well, maybe should you describe us your hardware and the C* release toi are using. Also give us some metrics.
I have troubles finding some quantitative information as to how a healthy Cassandra node should look like (CPU usage, number of flushes,SSTables, compactions, GC), given a certain hardware spec and read/write load. I have troubles gauging our first and only Cassandra node, whether it needs tuning or is simply overloaded.
If anyone could point me to some data that would be very helpful.
(So far I have run the node with the default settings in cassandra.yaml and cassandra-env. The log claims that the server is occasionally under memory pressure and I get frequent timeouts for writes. I see what I think are many flushes, compactions and GCs in the log. Some toying with heap and new gen sizes, key cache, and the compaction throughput settings did not improve the overall situation much.)