A Case for Service Differentiation in SANs

Motivated by the need to simplify data sharing and curb rising storage management costs, storage systems are becoming increasingly consolidated. This is in turn leading to large and complex storage area networks connecting hundreds of storage devices and servers. Database, mail, multimedia and file servers, for example, gain access to a shared pool of storage devices through a common storage area network. The traffic carried over such storage networks is therefore increasinly heterogeneous, both in terms of its characteristics as well as its utility and its relative importance and value to the organization. Contrary to widespread misconceptions, storage network bandwidth is not overly abundant, and many deployed networks are reported to be oversubscribed. In this paper, we argue that storage area networks should provide di erentiated services to storage traffic to ensure that the performance of business critical applications is not unduly harmed by low-priority batch traffic such as backup and long running data mining applications. In particular, we discuss the challenges of providing differentiated services in storage networks and, building on previous work addressing a similar problem in wide-area networks, we present an architecture that achieves such differentiation in practice. Furthermore, we propose a mechanism to ensure proper bandwidth allocation in the particular case of Fibre Channel Arbitrated Loop, which is the most widely deployed Fibre Channel network topology.

By: Khalil S. Amiri, Kang-Won Lee

Published in: RC22757 in 2003


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