@InProceedings{barve:round, author = {Rakesh Barve and Phillip B. Gibbons and Bruce K. Hillyer and Yossi Matias and Elizabeth Shriver and Jeffrey Scott Vitter}, title = {Round-like Behavior in Multiple Disks on a Bus}, booktitle = {Proceedings of the Sixth Workshop on Input/Output in Parallel and Distributed Systems}, year = {1999}, month = {May}, pages = {1--9}, publisher = {ACM Press}, address = {Atlanta, GA}, URL = {http://vibes.cs.uiuc.edu/IOPADS/Accepted/Shriver.ps}, keywords = {disk, I/O bus, parallel I/O, pario-bib}, abstract = {In modern I/O architectures, multiple disk drives are attached to each I/O bus. Under I/O-intensive workloads, the disk latency for a request can be overlapped with the disk latency and data transfers of requests to other disks, potentially resulting in an aggregate I/O throughput at nearly bus bandwidth. This paper reports on a performance impairment that results from a previously unknown form of convoy behavior in disk I/O, which we call rounds. In rounds, independent requests to distinct disks convoy, so that each disk services one request before any disk services its next request. We analyze log files to describe read performance of multiple Seagate Wren-7 disks that share a SCSI bus under a heavy workload, demonstrating the rounds behavior and quantifying its performance impact.} }