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OSDI 2000 Abstract
Towards Higher Disk Head Utilization:
Extracting Free Bandwidth From Busy Disk Drives
Christopher R. Lumb, Jiri Schindler,Gregory R. Ganger,
David F. Nagle, Carnegie Mellon University, and Erik Riedel, Hewlett-Packard Labs
Abstract
Freeblock scheduling is a new approach to utilizing more of a disk's potential media bandwidth. By filling
rotational latency periods with useful media transfers, 20-50% of a never-idle disk's bandwidth can often be
provided to background applications with no effect on foreground response times. This paper describes freeblock
scheduling and demonstrates its value with simulation studies of two concrete applications: segment cleaning and
data mining. Free segment cleaning often allows an LFS file system to maintain its ideal write performance when
cleaning overheads would otherwise reduce performance by up to a factor of three. Free data mining can achieve
over 47 full disk scans per day on an active transaction processing system, with no effect on its disk performance.
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