The paper "A Case for Redundant Arrays of Inexpensive Disks (RAID)" by David A. Patterson, Garth Gibson, and Randy H. Katz introduces the concept of RAID, a method to improve the performance, reliability, power consumption, and scalability of I/O systems using arrays of inexpensive disks. The authors highlight the limitations of Single Large Expensive Disks (SLED) in terms of performance and capacity, while noting that the capacity of personal computer disks has grown rapidly. RAID offers a solution by leveraging the lower cost and higher capacity of these disks, with the promise of significant improvements in performance. The paper outlines five levels of RAID, each with different cost-performance characteristics and reliability levels. Level 1, or mirrored disks, provides the highest performance but is the most expensive. Levels 2 and 3 reduce costs by using Hamming code for error correction and single check disks per group, respectively. Level 4 improves performance for small transfers by interleaving data across all disks, while Level 5 further enhances performance by distributing data and check information across all disks, allowing multiple individual writes per group. The authors compare RAID to the IBM 3380 and Fujitsu Super Eagle, showing that RAID can offer a factor of 10 improvement in performance, reliability, and power consumption, with a reduction in size. They also discuss the modular growth capabilities of RAID and its potential to replace SLEDs in future I/O systems. The paper concludes by emphasizing the advantages of RAID in meeting the challenge of exponential growth in processor and memory speeds, while acknowledging open issues such as latency and practical implementation details.The paper "A Case for Redundant Arrays of Inexpensive Disks (RAID)" by David A. Patterson, Garth Gibson, and Randy H. Katz introduces the concept of RAID, a method to improve the performance, reliability, power consumption, and scalability of I/O systems using arrays of inexpensive disks. The authors highlight the limitations of Single Large Expensive Disks (SLED) in terms of performance and capacity, while noting that the capacity of personal computer disks has grown rapidly. RAID offers a solution by leveraging the lower cost and higher capacity of these disks, with the promise of significant improvements in performance. The paper outlines five levels of RAID, each with different cost-performance characteristics and reliability levels. Level 1, or mirrored disks, provides the highest performance but is the most expensive. Levels 2 and 3 reduce costs by using Hamming code for error correction and single check disks per group, respectively. Level 4 improves performance for small transfers by interleaving data across all disks, while Level 5 further enhances performance by distributing data and check information across all disks, allowing multiple individual writes per group. The authors compare RAID to the IBM 3380 and Fujitsu Super Eagle, showing that RAID can offer a factor of 10 improvement in performance, reliability, and power consumption, with a reduction in size. They also discuss the modular growth capabilities of RAID and its potential to replace SLEDs in future I/O systems. The paper concludes by emphasizing the advantages of RAID in meeting the challenge of exponential growth in processor and memory speeds, while acknowledging open issues such as latency and practical implementation details.