The Organization of This Book

This book takes you through a progression of concepts that in the end should provide a foundation for understanding storage networking infrastructures and applications. It assumes no prior knowledge of SANs and yet attempts to strike a balance between basic and advanced content. Hopefully, this mix will provide sufficient technical detail for those who need it and meaningful overview for those who want to understand SAN technology at a more abstract level.

The first two chapters provide a framework for understanding the central concepts of shared storage. Chapter 1 reviews the SNIA Shared Storage Model, which clearly abstracts the basic layers of storage applications and underlying infrastructure. The SNIA Shared Storage Model is a useful tool for understanding SAN architectures and positioning them in relation to upper-layer application requirements. It has also proven to be a useful tool for justifying SAN acquisitions to management by explaining how a particular solution will better serve business requirements. Chapter 2 provides an overview of storage and networking concepts and explains how the fusion of these ideas has created new means to solve data storage issues.

Because Fibre Channel was the first transport to appear on the storage networking scene and continues to ship in significant volumes, the next three chapters provide a technical discussion of Fibre Channel protocols, topologies, and products. Chapter 3 reviews lower-layer physical transport, protocols, and addressing. Chapter 4 reviews Fibre Channel topologies, with emphasis on the Fibre Channel fabric switch services provided by most SAN solutions today. Chapter 5 describes the product suite developed by vendors for Fibre Channel servers, storage, interconnects, and other components. Collectively, they provide a rich toolset for the SAN architect in designing efficient solutions.

Beginning in 2000, the initiative to transport storage data over mainstream TCP/IP networks generated IP storage networking architectures and products. These products further enhance the ability of SAN designers to craft shared storage configurations that leverage IP exclusively or integrate both IP and Fibre Channel into a heterogeneous storage network. Chapter 6 reviews the protocols and issues unique to IP SANs, and Chapter 7 describes IP storage products that have been introduced to the market over the past two years.

Chapter 8 provides an overview of storage-specific applications supported by the SAN infrastructure. Server clustering for high-availability data access, tape backup for data archiving, and data replication via disk mirroring are commonly deployed as part of a SAN solution, although these storage applications in turn are intended to serve high-level customer business applications and databases.

Inevitably, the gains provided by SANs are accompanied by some pain. Although vendors attempt to debug and certify SAN configurations in advance, problems naturally arise during installation or subsequent operation. Chapter 9 explains some basic troubleshooting techniques and tools for identifying and isolating storage network problems.

Chapter 10 discusses SAN management and its unique challenges. Managers of shared storage must integrate transport management with management of data placement on disk or tape. Creating a unified management capability has been difficult, even for software vendors with ample resources to address SAN management. The Common Information Model (CIM) initiative, however, is at last getting traction in the industry and may provide the framework required for comprehensive management of storage networks.

Chapter 11 attempts to describe the amorphous entity known as "storage virtualization." Storage virtualization has suffered somewhat from excessive vendor marketing, but is a viable technology for simplifying storage administration and opening a broader market for SAN solutions. This chapter covers the theoretical capabilities of storage virtualization as well as the more limited functions currently available in shipping products.

Institutions and enterprises have been implementing SANs for a wide variety of applications. Some of these are discussed in Chapter 12, Application Studies, with examples of potential issues customers might face in the course of deploying and administering SANs. Where applicable, combinations of Fibre Channel and IP storage products are proposed, especially for addressing metropolitan and wide area SAN configurations.

Chapter 13 discusses the still unresolved issues of SAN technologies, including interoperability, management, and convergence of SANs with mainstream networking. For engineers, these issues are simply challenges to be mastered, provided that market competition does not artificially thwart their efforts.

As a summary of SAN design, Chapter 14 offers speculation on the future of storage networking. That future promises to be as dynamic as the emergence of SANs was, with the rapid development of new storage initiatives such as virtualization and IP-based SANs, and accommodation of new host interconnects such as InfiniBand.

In this edition I have included in the appendixes additional material that may be useful as reference or background information on storage networking in general. The SNIA has produced some very valuable work in the form of the SNIA Shared Storage Model and the SNIA Dictionary. I encourage vendors as well as consumers of storage networking technology to take advantage of the SNIA's ongoing work and, when possible, to participate in SNIA activities. The more closely customers and technologists align their common goals, the more quickly viable solutions can be put into customers' hands.