The article provides a comprehensive overview of disk arrays, focusing on their design, performance, and reliability. It introduces the concept of data striping and redundancy, which are key techniques used in disk arrays to improve performance and reliability. The article discusses seven RAID (Redundant Arrays of Inexpensive Disks) levels (0-6) and compares their performance, cost, and reliability. It also explores advanced topics such as improving small write performance, declustered party, exploiting online spare disks, and data striping in disk arrays. The article includes case studies of existing disk array prototypes and products, and discusses future research opportunities, including scalability, latency, and interaction among new organizations. The authors aim to provide a systematic tutorial and survey of disk arrays, addressing the complex trade-offs between reliability, performance, and cost.The article provides a comprehensive overview of disk arrays, focusing on their design, performance, and reliability. It introduces the concept of data striping and redundancy, which are key techniques used in disk arrays to improve performance and reliability. The article discusses seven RAID (Redundant Arrays of Inexpensive Disks) levels (0-6) and compares their performance, cost, and reliability. It also explores advanced topics such as improving small write performance, declustered party, exploiting online spare disks, and data striping in disk arrays. The article includes case studies of existing disk array prototypes and products, and discusses future research opportunities, including scalability, latency, and interaction among new organizations. The authors aim to provide a systematic tutorial and survey of disk arrays, addressing the complex trade-offs between reliability, performance, and cost.