Cmg 92 Reno

Author : Bruce L. Worthington
Publisher :
ISBN 13 :
Total Pages : 514 pages
Book Rating : 4.3/5 (91 download)

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Download or read book Aggressive Centralized and Distributed Scheduling of Disk Requests written by Bruce L. Worthington and published by . This book was released on 1995 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: "Disk request scheduling is a critical element of high- performance computer system design. Previous disk scheduling research is insufficient because it uses simplistic or outdated disk models, unrepresentative workloads, and inadequate performance metrics. This dissertation explores the disk scheduler design space and provides guidelines for computer system engineers. Host-based and disk-based centralized scheduling are compared with distributed scheduling, a new paradigm with cost, complexity, and performance advantages. In distributed scheduling, individual disk schedulers located at multiple points along the I/O path cooperate to make scheduling decisions. Scheduler implementations are evaluated using a detailed simulator containing validated models of state-of-the-art host systems, controllers, buses, and disk drives. The simulator is driven with extensive traces of real-world system and disk activity, and it reports system performance metrics (e.g., application run times) in addition to traditional disk subsystem metrics (e.g., mean request response times). It is shown that for the best system performance, scheduling algorithms must incorporate system-level information (e.g., request priorities). Scheduling algorithms that focus on reducing seek delays do not need extensive disk-specific information. Finally, algorithms must exploit a disk's on-board cache to achieve the lowest disk service times. Additional guidelines are provided for dealing with disk drive command queues, sequential disk request optimizations, and different on-board cache configurations."