> average queue size column too. But given the vmstat output I doubt > this is the case since you should either be seeing a lot more wait > time or a lot less idle time.
Hmm, another thing: you mention 16 i7 cores. I presume that's 16 in total, counting hyper-threading? Because that means 8 threads should be able to saturate 50% (as perceived by the operating system). If you have 32 (can you get this yet anyway?) virtual cores then I'd say that your vmstat output could be consistent with READ-ROW-STAGE being CPU bound rather than disk bound (presumably with data fitting in cache and not having to go down to disk). If this is the case, increasing read concurrency should at least make the actual problem more obvious (i.e., achieving CPU saturation), though it probably won't increase throughput much unless Cassandra is very friendly to hyperthreading.... -- / Peter Schuller
