Dear all, I'm working with a 12-node, RF=3 cluster on low-end hardware (core i5 with 16GB of RAM & SATA disks). I'm using a BOP and each node has a load between 50GB and 100GB (yes, I apparently did not set my tokens right... I'll fix that later).
I'm hitting the cluster with a little over 100 concurrent threads during reads & writes in counter columns & plain columns. When I peek at my various servers & look at my munin graphs, it looks like everything is great : iostat -dmx shows peeks of 5% utilization at worst and vmstat shows peeks of 30% CPU utilization, no swapping and plenty of caching. Munin shows me that the JVM's heap is prancing around 50% of its allocated amount (and I have no row caching for now). So my thinking has been that the cluster is under-utilized but when I increase the number of threads hitting the cluster, I do not see the throughput increase which has been puzzling. I do see an occasional TimedOutException now that I've made my batches smaller (to dozens of mutations rather than hundreds) and my slices smaller too. What I do see is that each server in the cluster has about 60-80Mb/s traffic in & out and I'm running on 100Mb ethernet. I seem to remember that you can only get to a little over 80% of the available ethernet bandwidth in real-life. Could my performance be limited by the Network Adapters ? Thanks
