To determine an appropriate throughput limit, you should monitor performance from the cluster. You should not use a tool on the host to monitor performance. A host can report different results than the cluster.
Storage QoS limits I/O to and from the cluster. The rate of I/O that the cluster experiences can be different from what an application experiences. For example, reads from the application can go to the file system buffer cache and not to the cluster.
Due to this behavior, you should monitor performance from the cluster and not from a host-side tool.