Linux系统下基于SCST的SCSI target驱动设计

摘要

随着信息数字化的深入发展，数据存储的需求日益增长。存储虚拟化带给我们最直接的益处就是，提高存储利用率，降低成本，简化存储管理，而基于网络的虚拟存储技术将成为未来的一种趋势，它的开放性、扩展性、管理性等方面的优势将在数据大集中、异地容灾等应用中充分体现出来。存储局域网(SAN)是一种高性能，扩展性极强的存储系统模型，近年来应用非常广泛。FC-SAN是一种基于光纤通道协议的存储局域网，它通过光纤传输SCSI指令和数据。本文详细论述了Linux系统下基于SCST的SCSI target驱动设计原理与实现。SCST是Linux系统下一个为了简化SCSI 驱动设计而开发的一个SCSI子系统层。SCSI target驱动应用于存储局域网(SAN), 它与光纤通道HBA卡协同工作，处理和响应SCSI发起端的I/O请求，实现存储虚拟化和存储分配功能。整个SCSI target驱动分三层模块，最底层模块处理与HBA卡通信，解析SCSI指令和数据并传递给上层驱动处理。虚拟磁盘模块则响应I/O请求，完成数据的最终读写操作。这三个模块均以内核模块的方式嵌入Linux内核。

关键词：　虚拟存储，SCSI，SAN，SCST，光纤通道

Abstract

With the deepening development of digital information, demand for data storage is increasing dramatically. The basic benefits that storage virtualization brings to us are increment in storage utilization rate increment, cost cutting and simplification in storage management. As network starge virtualization is becoming the trend of future technology, its advantages in compatibility, expansibility and quality management will be fully seen in the applications such as data concentration and different area disaster recovery. Storage area network(SAN) is a storage system model with excellent performance and scalability that has been widely used in recent yeas.FC-SAN is baed on the fibre channel transport protocol,which allows SCSI commands and data transmits on fibre channels.This assay descripts the design and implemention of SCSI target driver based on SCSI under linux operation system. SCST is a SCSI subsystem for linux,it simplify the design of scsi target driver. SCSI target driver works with Host bus adapters,processes and responses to I/O requests from initiators on storage area network.It realizes storage virtualization and distribution.The whole SCSI target driver is a three-tier system.The lowest module communicates host bus adapters,parses SCSI commands and data,then pass them to the top module.The virtual disk module response the I/O requests and do the real data read and write operations.