I'm doing some benchmarking with IOMeter, and I'm seeing a consistent and susbtantial drop-off in performance after running the first test in my VMWare environments. These drop-offs are about the same on the three VMs I've tested on, which makes me think it's a configuration setting, or something about my VMs.
For example, one system (local RAID 10) went from 388 I/Os per second the first run, to about 211 I/Os per second on every run after that. Everything else about the test was identical, and I also bounced the machine in between runs. Testing on my local machine in a non-virtualized environment is consistent, whereas if I test it with a local VM, I also get a performance drop-off after the first run.
Any explanations or suggestions to explore?