RAID-II: a high-bandwidth network file server

Abstract

In 1989, the RAID (Redundant Arrays of Inexpensive Disks) group at U. C. Berkeley built a prototype disk array called RAID-I. The bandwidth delivered to clients by RAID-I was severely limited by the memory system bandwidth of the disk array' s host workstation. We designed our second prototype, RAID-H, 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. RAID-II runs 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 for large, random read operations and up to 31 megabytes/second for sequential read operations. A preliminary implementation of LFS on RAID-II delivers 21 megabytes/second on large read requests and 15 megabytes/second on large write operations.