Quality of service (QoS) is a critical enabling technology for enterprises and service providers wanting to deliver consistent primary storage performance to business-critical applications in a multi-tenant or enterprise infrastructure. The type of applications that require primary storage services typically demand greater levels of performance than what is readily available from traditional storage infrastructures today. However, simply providing raw performance is often not the only objective in these use cases. For a broad range of business-critical applications, consistent and predictable performance are the more important metrics. Unfortunately, neither is easily achievable within traditional storage arrays.