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Abstract : |
In 1989, the RAID group at U. C. Berkeley built a prototype disk array called RAID-I. The bandwidth achieved by RAID-I was severely limited by the memory system bandwidth limitations of the disk array's host workstation. As a result, most of the bandwidth available from the disks could not be delivered to clients of the disk array #le server. We designed our second prototype, RAID-II, to deliver as much of the disk array bandwidth as possible to #le server clients. A custom-built circuit-board disk array controller, called the XBUS board, connects the disks and the high-speed network directly, allowing data for large requests to bypass the server workstation. A single workstation may control several XBUS boards for increased bandwidth. RAID-II runs the Log-Structured File System #LFS # to optimize the performance of the disk array for bandwidth-intensive applications. The RAID-II hardware with a single XBUS controller board delivers 20 megabytes#second of I#O between the disks and high-speed networks. This performance is an order of magnitude better than our #rst prototype, but somewhat lower than our performance goals because of lower-than-expected performance of the commercial disk controller boards and our disk system interfaces. A preliminary implementation of LFS delivers 13.4 megabytes#second to the clients., |
