This paper envisions a distributed network storage service with Quality-of-Service (QoS) guarantees and describes its architecture and key mechanisms. When fully realized, this service architecture would be able to support, in one integrated framework, network storage services ranging from best-effort caching to replication with performance guarantees. Content owners could, through the use of standardized protocols, reserve network storage resources to satisfy their application-specific performance requirements. They would be able to specify either the number and/or placement of the replicas, or higher-level performance goals based on access latency, bandwidth usage or data availability. The network storage provider would then optimally allocate storage resources to meet the service commitments, using leftover capacity for best-effort caching. Content consumers would then retrieve the nearest copy of the data object, be it from a replica, cache, or the original source, in a completely transparent manner. Furthermore, a distributed network storage infrastructure should be integrated with the existing transmission-based QoS framework so that applications can select the optimal combination of storage and transmission resources to satisfy their performance requirements.
This work identifies and discusses key research areas and problems that need to be tackled, including those in service specification, resource mapping, admission control, resource reservation and real-time storage management. The paper establishes a QoS framework upon which community discussion on this vision can proceed.