We recommend creating a prime client in addition to as many clients as you need to run your tiles. So, for 1 tile, you would have a prime client and one additional client, "client0", for tile 0.
The Benchmarking Guide indicates this under "Client Software Requirements" as
Each VMmark tile requires a client machine and each VMmark testbed requires one prime client. If desired, the prime client can also serve as a client for the first tile (which would make it both the prime client and client0).
For another example of this, check the "Hosts File Worksheet" where the primeclient IP address is listed separately from the virtualclient0, virtualclient1... IP addresses.
The prime client runs the VMmark harness and its operating system must be installed natively (a physical client). All other clients may be physical clients or virtual clients, and they serve requests to the workload VMs. It's common to set up VMmark so the prime client, which requires special software, is a physical machine, while all the clients are identical virtual machines (except for their IP and domain membership, etc.). In this case, the prime client only runs the harness, and does not handle workloads like a regular client.
However, it is possible to use the prime client physical machine also as "client0" so that it runs the harness and serves requests to the workload VMs. The setup you choose usually depends on how much hardware you have available to run client machines.
Please let me know if I can answer any more questions.
Thanks,
Rebecca