Quality-of-Service (QoS) is a means to ensure specific performance levels for applications and workloads. In general there are two ways to accomplish this:
1. Ability to set limitations to avoid unwanted behavior from non-critical VMs.
2. Ability to set guarantees to ensure service levels for mission-critical VMs.

Nutanix ECP Storage QoS provides administrators granular control to manage the performance of VMs and ensure that the system delivers consistent performance for all workloads. Administrators can limit the IOPS for individual VMs. IOPS is the number of requests the storage layer can serve in a second. Throttling IOPS on VMs is used to prevent noisy VMs from over-utilizing the storage system resources. Nutanix ECP Storage QoS is availabe in the Ultimate and Pro edition.

Nutanix AOS 5.0 enhanced performance reliability by introducing separate internal Read and Write I/O Queues so write-intensive workloads (or write bursts) will not starve out read operations, and vice-versa. This behavior is non-tunable.