iSCSI：连接通用存储的网络技术详解 - CSDN文库

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《iSCSI：通用存储连接》是一本由John L. Hufferd所著的专业书籍，由Addison Wesley出版社于2002年11月出版，ISBN号为0-201-78419-X，共368页。这本书的目的是为网络、内部网以及互联网上的数据存储专业人士提供关于新兴的iSCSI标准的全面介绍和深入指南。iSCSI技术的核心在于通过网络实现数据存储、访问和管理，显著降低了共享存储解决方案的总拥有成本，促进了不同系统（包括服务器级系统、笔记本电脑和台式机）以及数据的整合。 iSCSI协议的关键特性使得组织能够将分散的系统和数据统一起来，这对于企业来说具有极大的价值，因为许多顶级科技公司如IBM、Cisco Systems和Intel等都在积极支持iSCSI的发展。该书详尽地探讨了iSCSI技术的各个方面，包括会话建立、错误处理等，以及它与基础的SCSI协议之间的关系，后者是iSCSI发展的重要起点。书中具体涵盖了以下几个关键话题： 1. **iSCSI概述**：介绍了iSCSI的基本概念，解释了为何它是当前存储网络架构中的重要组件，以及它如何利用TCP/IP协议进行数据传输。 2. **协议架构**：详细解析了iSCSI协议栈，包括发现、会话管理、数据块传输、认证和错误恢复等各个阶段的运作机制。 3. **与SCSI的关系**：讨论了iSCSI如何继承并扩展了SCSI的功能，使其能够在远程环境中提供类似本地存储的性能。 4. **部署策略**：针对不同的环境，如数据中心、远程办公室和云存储，提供了实施iSCSI的最佳实践和策略。 5. **兼容性与标准化**：阐述了iSCSI与业界其他存储接口的兼容性，以及它在不同标准和规范中的地位。 6. **安全性与管理**：涵盖了iSCSI的安全措施，如IPSec和CHAP认证，以及如何有效地管理和监控iSCSI环境。 7. **案例研究和未来趋势**：书中还可能包含实际案例分析，展示了iSCSI在不同组织中的应用成功，以及预测了iSCSI技术的未来发展方向。《iSCSI：通用存储连接》不仅是一本技术手册，也是一份战略参考资源，为读者提供了理解、实施和优化iSCSI存储解决方案的必要知识。对于任何关注存储网络演进或寻求提高存储效率的读者来说，这是一本不可多得的参考资料。

SCSI Bus Interconnect

A SCSI bus permits hard disks, tape drives, tape libraries, printers, scanners, CD-ROMs, DVDs, and the like

to be connected to server systems. It can be considered a general interconnection technique that permits

devices of many different types to interoperate with computer systems. (See Figure 1-1.)

Figure 1-1. Small computer system interface (SCSI).

The protocol used on the SCSI bus is the SCSI Protocol. It defines how the SCSI device can be addressed,

commanded to perform some operation, and give or take data to or from the (host) computing system. The

operational commands are defined by a data structure called a command description block (CDB). For

example, a read command would have a CDB that contained an "opcode" defined by the protocol to mean,

"read." It would also contain information about where to get the data (e.g., the block location on the disk) and

miscellaneous flags to further define the operation.

The protocol that defines how a SCSI bus is operated also defines how to address the various units to which

the CDB will be delivered. Generally, presenting the address on the hardware lines of the SCSI bus performs

the addressing. This address technique calls out a particular SCSI device, which may then be subdivided into

one or more logical units (LUs). An LU is an abstract concept that can represent various real objects such as

tapes, printers, and scanners.

Each LU is given an address. This is a simple number called the logical unit number (LUN). Thus, the SCSI

protocol handles the addressing of both the SCSI device and the LU. (Note: "LUN," though technically

incorrect, will often be used when "LU" is meant.) Servers may connect to many SCSI buses; in turn the SCSI

buses can each connect to a number of SCSI devices, and each SCSI device can contain a number of LUs (8,

16, 32, etc.). Therefore, the total number of SCSI entities (LUs) attached to a system can be very large. (See

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SCSI Bus Interconnect 16

Fibre Channel Interconnect

Understanding the problems with SCSI led a number of vendors to create a new interconnection type known

as Fibre Channel. In this technology the SCSI CDBs are created in the host system, as they were in SCSI bus

systems; however, the SCSI bus is replaced with a physical "fibre channel" connection and a logical

connection to the target storage controller.

The term "logical connection" is used because Fibre Channel (FC) components can be interconnected via hubs

and switches. These interconnections make up a network and thus have many of the characteristics found in

any network. The FC network is referred to as an FC storage area network (SAN). However, unlike in an

Internet Protocol (IP) network, basic management capability is missing in Fibre Channel. This is being

rectified, but the administrator of an IP network cannot now, and probably never will be able to, use the same

network management tools on an FC network that are used on an IP network. This requires duplicate training

cost for the FC network administrator and the IP network administrator. These costs are in addition to the

costs associated with the actual storage management duties of the storage administrator.

I have had many storage customers request that storage be set up on an IP network, for which they have

trained personnel. (See Figure 1-5.) This request comes from the fact that FC networking has not been taught

in colleges and universities.

[*]

People with FC skills are generally taught by the vendor or by specialty

schools, which are paid for by their company. This is a very expensive burden that must be borne by the

customer of FC equipment. The more storage shipped that is FC connected, the more ruthless the demand for

trained personnel. Without universities providing trained graduates, companies will keep hiring people away

from each other.

[*]

There is at least one important exception: the University of New Hampshire, which has

become an important center for interoperability testing for Fibre Channel (and recently for

iSCSI).

Figure 1-5. Have versus want.

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Fibre Channel Interconnect 20

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