Preface

THE FOLLOWING WORK provides an overview of a new technology for creating storage area networks (SANs) with conventional Transmission Control Protocol/Internet Protocol (TCP/IP) and Gigabit Ethernet networking. IP-based storage networking continues the work initially started by Fibre Channel of providing flexible, high-performance block data access for storage applications. SANs have already proved their practical value in facilitating applications such as server clustering, storage consolidation, and tape backup. With continued market momentum, storage networking is expected to capture more than half the new storage deployments within the next few years.

The unique contribution of storage over IP solutions is the ability to integrate storage networking into mainstream data communications. For customers, the economies of scale provided by common infrastructure and common management make a compelling argument for the adoption of IP SANs, whereas Fibre Channel, despite the effort of certain authors, is still viewed as problematic and must be maintained as a separate network. As often happens in high-technology fields, one group of vendors breaks the very hard ground of technical issues, only to see others behind them sowing and reaping the newly tilled and now-fertile soil.

Although IP storage can leverage many of the advances made by Fibre Channel, it has its own issues to address. The Internet Engineering Task Force (IETF) is currently working on multiple protocols for transporting block data over IP networks. The IETF activity consists of ongoing discussions on the requirements of storage data over IP and a series of Internet drafts that embody the work in progress. A detailed analysis of the standards specifications for these protocols is well beyond the scope of this short book, and well beyond the endurance of its author. The IP storage technical documentation, however, is readily available on the IETF Web site listed in the bibliography. The curious reader will also find there the latest versions of standards drafts and Requests for Comments (RFCs) for auxiliary protocols such as security and quality of service, which would be quickly outdated if included here.

The scope of the following text also includes an overview of Fibre Channel technology. This is provided as a basis to appreciate the challenges of IP storage and to acquaint readers from the internetworking world with SAN concepts first aired by Fibre Channel. As with IP storage specifications, this book cannot detail Fibre Channel standards. For granular detail, the reader may reference Robert Kembel's Fibre Channel Consultant series, which includes a recent book on fabric switches, or the reader may examine the appropriate Fibre Channel standards directly. A more comprehensive overview of Fibre Channel topologies and products is also included in my previous work, Designing Storage Area Networks.

This book is intended for information technology (IT) managers, administrators, consultants, and technical staff responsible for networking and storage management. Storage and networking have traditionally resided in two distinct worlds. Typically, people from an internetworking background are not familiar with storage issues, whereas storage administrators may need to know little about IP internetworking. Storage networking is a melding of these technologies into an integrated solution. IP storage networking offers some relief to networking personnel because the interconnects, bandwidth provisioning, and transport management for IP SANs are drawn from mainstream IP networking. For storage administrators, understanding IP storage is also facilitated by the more accessible expertise within IT staff who are already familiar with the IP component of IP SANs. To satisfy readers from both worlds, this text does not assume prior knowledge of either IP networking or storage concepts. The respective readers may skim at will through material they already understand and may dwell on the passages that contain new content. Although it is difficult to write a single book for such a potentially diverse readership, it is hoped that regardless of specific technical background, the reader will in the end close the cover with an understanding of the benefits that IP storage can provide.

The particular prejudices at work throughout the text will become obvious. Fibre Channel was a pioneering technology. It was the first to develop and implement successfully in viable products a number of new capabilities that have benefited IT in general. A stable and relatively error-free switched gigabit transport, a fully functional serial protocol for block data transmission, and innovative treatment of networked servers and storage have been leveraged by IP storage vendors to accelerate the development of IP SANs. Despite the technical attributes of Fibre Channel, however, historical momentum and massive resources are on the side of IP and Gigabit Ethernet technology. Although Fibre Channel storage solutions will continue to ship in significant volumes for some time to come, the tide of storage networking will eventually turn at customer direction toward the network infrastructure that already dominates mainstream data communications. The challenge for all storage network vendors and customers alike will be to make this transition as painless as possible.