The Architecture and Design of HS-series StorageWorks Array Controllers

This document provides a comprehensive overview of the HS-series StorageWorks array controllers (including models HSJ30, HSJ40, HSD30, and HSZ40). It details the product goals, which focused on achieving open systems capability, high availability through dual-redundant configurations and parity RAID technology, and high performance via optimized controller throughput, latency, and hardware acceleration (such as the FX chip for XOR operations). The paper explains key design choices, including the use of SCSI-2 as a device interconnect, the development of a common hardware platform to manage costs and complexity, and the implementation of a battery-backed nonvolatile write-back cache to eliminate the 'write hole' and enhance performance. Finally, it outlines the system's fault-tolerant mechanisms, such as automatic failover and hot-swappable components, designed to meet the rigorous demands of enterprise storage environments.