In this paper, we propose a quality of service (QoS) aware transport solution for storage access over data center network. Motivation for QoS differentiation comes from the emerging storage technologies which not only provide network comparable latency but also overwhelm the network bandwidth close to the storage servers. We consider both throughput and latency related QoS requirements and demonstrate how they can be enforced by Explicit Congestion Notification (ECN) enabled switches. The mechanism can be viewed as a way of adding QoS capability to the existing data center transport solutions. Our scheme can co-exist with existing congestion management schemes and ensures RTT fairness while providing service differentiation. We show that our scheme can provide differentiated treatment and besides achieving better throughput fairness during the congestion episode, our solution can reduce the target latency misses by up to 71% and 80% as compared to the existing TCP and RDMA transport.