Computer Science Department
School of Computer Science, Carnegie Mellon University


D-SPTF: Decentralized Request Distribution in Brick-based Storage

Christopher R. Lumb, Gregory R. Ganger, Richard Golding*

November 2003

Keywords: Decentralized storage, storage systems, array scheduling, scalability

Distributed Shortest-Positioning Time First (D-SPTF) is a request distribution protocol for decentralized systems of storage servers. D-SPTF exploits high-speed interconnects to dynamically select which server, among those with a replica, should service each read request. In doing so, it simultaneously balances load, exploits the aggregate cache capacity, and reduces positioning times for cache misses. For network latencies of up to 0.5ms, D-SPTF performs as well as would a hypothetical centralized system with the same collection of CPU, cache, and disk resources. Compared to existing decentralized approaches, such as hash-based request distribution, D-SPTF achieves up to 65% higher throughput and adapts more cleanly to heterogenous server capabilities.

20 pages

*IBM Almaden Research

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