RAID-II: A high-bandwidth network file server

Ann L. Chervenak, Ken Shirriff, John H. Hartman, Ethan L. Miller, Srinivasan Seshan, Randy H. Katz, Ken Lutz, David A. Patterson, Edward K. Lee, Peter M. Chen, Garth A. Gibson

Research output: Chapter in Book/Report/Conference proceedingChapter


In 1989, the RAID (Redundant Arrays of Inexpensive Disks) 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 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 RAID-I file server. We designed our second prototype, RAID-II, to deliver more of the disk array bandwidth to file server clients. A custom-built crossbar memory system called the XBUS board connects the disks directly to the high-speed network, allowing data for large requests to bypass the server workstation. A single workstation can control several XBUS boards for increased bandwidth. RAID-II runs the Log-Structured File System (LFS) software to optimize performance for bandwidth-intensive applications. The RAID-II hardware with a single XBUS controller board delivers 20 megabytes/second of raw I/O between 24 disks and the high-speed network for large, random read operations and up to 31 megabytes/second for sequential read operations. This is an order of magnitude better than our first prototype, but lower than our performance goal of 40 megabytes/second because of lower-than-expected performance of the commercial disk controller boards and our disk system interfaces. A preliminary implementation of LFS software on RAID-II configured with 24 disks delivers 13.4 megabytes/second on large read requests.

Original languageEnglish (US)
Title of host publicationHigh Performance Mass Storage and Parallel I/O
Subtitle of host publicationTechnologies and Applications
PublisherWiley-IEEE Press
Number of pages12
ISBN (Electronic)9780470544839
ISBN (Print)0471208094, 9780471208099
StatePublished - Jan 1 2001


  • Arrays
  • Bandwidth
  • File servers
  • Hardware
  • Prototypes
  • Servers
  • Workstations

ASJC Scopus subject areas

  • Computer Science(all)


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