Thanks for the quick reply. I did not try the "slow" test using a normal disk drive, however I first discovered this problem when writing to a 7200RPM disk drive at a much higher messaging rate (e.g. 1500 to 3000 creates/sec rather than 84 creates/sec). This is what caused me to start simplifying the configuration trying to find the root cause. As part of that investigation, I created a RAM disk to avoid the hard drive, but the hard drive wasn't the problem. I just haven't switched back to the hard drive.
I don't know what ZooKeeper is doing internally, or how & why it is deriving 76ms MAX latency. The very regular periodic pattern suggests something odd. Hmmmm.....
