You can specify one service-level objective for a Storage QoS policy group: a maximum throughput limit. A maximum throughput limit, which you define in terms of IOPS or MBps, specifies the throughput that the workloads in the policy group cannot collectively exceed.
When you specify a maximum throughput for a policy group, Storage QoS controls client operations to ensure that the combined throughput for all workloads in the policy group does not exceed the specified maximum throughput.
For example, assume that you create the policy group "untested_apps" and specify a maximum throughput of 300 MBps. You assign three volumes to the policy group. The combined throughput to those three volumes cannot exceed 300 MBps.
Note the following about specifying a maximum throughput:
For example, you can ensure that your critical workloads get the throughput that they need by limiting noncritical workloads.
For example, if you see an average utilization of 500 IOPS, you might specify a limit of 1,000 IOPS.