In some situations, throttling a workload (I/O to a storage object) can affect the performance of non-throttled workloads if the I/O requests are sent from the same client.
If a client sends I/O requests to multiple storage objects and some of those storage objects belong to Storage QoS policy groups, performance to the storage objects that do not belong to policy groups might be degraded. Performance is affected because resources on the client, such as buffers and outstanding requests, are shared.
For example, this might affect a configuration that has multiple applications or virtual machines running on the same host.
This behavior is likely to occur if you set a low maximum throughput limit and there are a high number of I/O requests from the client.
If this occurs, you can increase the maximum throughput limit or separate the applications so they do not contend for client resources.