Effective Quality of Service Differentiation for Real-world Storage Systems

Data storage is an integral part of IT infrastructures, where Quality of Service (QoS) differentiation amongst customers and their applications is essential for many. Achieving this objective in a production environment is nontrivial, because these environments are complex and dynamic. Numerous practical and engineering constraints render the task even more challenging. This paper presents SLED-2, a QoS differentiation solution that meets these challenges in offering effective protection to the performance of important workloads at the expense of less important workloads when needed. SLED-2 uses a customized feedback heuristic that rate-limits selected I/O streams. This approach is unique in that it accounts for a number of important practical considerations, including fine-grained controls, errors in storage systems models, and inexpensive and safe QoS management. SLED-2 has been implemented for the IBM DS8000 series storage servers and shown to be highly effective in a set of hostile and practical scenarios using test facilities for IBM storage products.