The worker VMs have to also be I/O Analyzer appliance VMs.
If the I/O Analyzer appliance VM doesn't run Iometer after the test is started, it's mostly due to network issues. Please double check whether you can SSH from the controller VM to all the worker VMs (including the controller VM itself). The backend script relies on SSH to invoke all worker Iometer processes.
For step by step instructions on using I/O Analyzer, refer to I/O Analyzer User's Guide p.p. 15-18.
Thanks,
Chien-Chia