Today's enterprises face unprecedented data storage and availability requirements. To meet these needs, they are increasingly turning to Storage Area Networks (SANs). Now, even more promising IP-based SANs are arriving, combining the advantages of SAN architecture with the familiarity and value of IP-based networking. Leading SAN expert Tom Clark surveys these emerging products, helping decision-makers understand the key issues, protocols, technologies, and applications. He begins with an overview of today's enterprise storage challenges and reviews existing approaches, including Fibre Channel, SCSI; and network-attached-storage solutions. He then introduces IP from the perspective of the storage professional. Clark reviews supporting technologies such as TCP offload engines; and presents in-depth coverage of security, including VLANs, encryption, and authentication. Case studies present IP SANs at work in server clustering, backup, storage consolidation, disaster recovery, and both metropolitan and wide-area IP storage networks. The book concludes with a developmental roadmap reflecting key advances such as 10 Gb Ethernet and Infiniband.
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(NOTE: Each chapter concludes with Chapter Summary.)
2. Shared Storage.
The SNIA Shared Storage Model.
Storage Networking Layers.
Packetizing of Data.
Routing of Packets.
Upper Layer Protocol Support.
Storage Networking Terminology.
Just a Bunch of Disks (JBODs).
SCSI over IP-to-Parallel SCSI Bridges.
Legacy SCSI Cabling.
Fibre Channel Layers.
FC-0 — Fibre Channel Physical Layer.
FC-1 — Fibre Channel Link Controls and Data Encoding.
FC-2 — Fibre Channel Framing, Flow Control and Class of Service.
FC-3 — Common Services.
FC-4 — Fibre Channel Upper Layer Protocol.
Fibre Channel Topologies.
Gigabit Ethernet Layers.
802.1Q VLAN Tagging.
802.1p/Q Frame Prioritization.
802.3x Flow Control.
802.3ad Link Aggregation.
Gigabit Ethernet Physical Layer Considerations.
Assumptions for IP-based SANs.
Operating Systems and SCSI I/O.
The SCSI Architectural Model (SAM-2).
Layer 2 Bridging.
Layer 3 - IP.
Address Resolution Protocol.
IP Network Example.
IP Routers and IP Switches.
Other IP Considerations.
Layer 4 - UDP.
UDP Port Numbers.
UDP for IP Storage Applications.
Establishing TCP Connections.
TCP Segment Size.
TCP Sliding Window and Congestion Control.
TCP Error Recovery.
Upper Layer Interface.
Standards-based IP Storage Protocols.
The IETF and IPS Working Group.
Fibre Channel over IP (FCIP).
FCIP and Timeout Values.
FCIP SAN Interfaces.
FCIP Error Handling.
FCIP Flow Control.
FCIP Quality of Service.
Internet Fibre Channel Protocol - iFCP.
iFCP Network Architecture.
iFCP Fabric Service Emulation.
iFCP and TCP Connection Control.
iFCP Error Handling.
Metro Fibre Channel Protocol - mFCP.
Internet SCSI - iSCSI.
iSCSI Network Architecture.
iSCSI Protocol Layering Model.
iSCSI Address and Naming Conventions.
iSCSI Session Management.
iSCSI Error Handling.
Device Discovery in Fibre Channel.
Discovery in IP Storage Networks.
iSNS Discovery Process.
iSNS State Change Notification and Entity Status Inquiry.
Securing Storage Data Transport.
Security in Fibre Channel SANs.
World Wide Name Zoning.
Security in IP Storage Networks.
Access Control Lists (ACLs).
Class of Service and Quality of Service.
802.1p Traffic Prioritization.
Type of Service (TOS).
Differentiated Services (DiffServ).
Resource Reservation Protocol (RSVP).
Multiprotocol Label Switching (MPLS).
InfiniBand and Storage Networking.
IP Storage in Data Center Applications.
Local Tape Backup.
IP Storage for Remote Applications.
Prerequisites for Successful IP Storage Deployment.
Integration with Other Storage Technologies.
IP Storage Futures.
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.
The following text provides an overview of multiple technologies that must eventually coexist within enterprise networks. Networks must necessarily maintain a medley of products as new technologies are introduced and as the most recent legacy-branded products are transitioned to less critical areas. For storage, a network may require support for direct-attached Small Computer Systems Interface (SCSI) disks and tape, Fibre Channel switches and storage, and the newly introduced IP storage devices. The text therefore devotes some space to examining the attributes of each storage technology with the aim of clarifying alternatives for technology convergence.
Chapter 1 provides a historical perspective on storage issues and what problems must be resolved to achieve viable, shared storage solutions. Because the Technical Council of the Storage Networking Industry Association (SNIA) has provided a general framework for understanding shared storage, Chapter 2 reviews the SNIA Shared Storage Model to position IP SANs within storage networking as a whole.
For successful deployment, storage over IP has dependencies on both legacy and current technologies. Chapter 3 examines storage networking transports and components, including SCSI and Fibre Channel, as well as the Gigabit Ethernet infrastructure on which IP storage itself resides. The foundation protocol for all storage networking solutions is provided by the SCSI Architectural Model, or SAM-2. The main features of the SCSI architecture are reviewed in Chapter 4.
Chapters 5, 6, and 7 cover IP, the User Datagram Protocol, and TCP respectively. These chapters are intended primarily for readers unfamiliar with IP concepts, although references are also made to features that affect IP SANs.
Chapter 8 examines the three IP storage protocols currently under development in the IETF. The Fibre Channel over IP (FCIP) protocol represents a Fibre Channel extension strategy and relies on IP only to connect remote Fibre Channel SANs. The Internet Fibre Channel Protocol (iFCP) maps IP addresses to Fibre Channel end nodes and enables the replacement of Fibre Channel fabrics with IP storage networking. The Internet SCSI (iSCSI) protocol enables replacement of Fibre Channel end devices with native IP storage devices, and thus represents a radical shift from current Fibre Channel deployments. These three protocols provide a spectrum of solutions, from simple Fibre Channel extension to migration to displacement.
The IP storage transport protocols are by no means the sole focus of the IETF standards initiatives. Management of IP SANs is also a critical issue. Chapter 9 reviews the Internet Storage Name Server (iSNS) protocol that has been supported by the IP storage community as a means of rationalizing discovery and management of IP storage devices and interconnects.
Two key components that have been lacking in Fibre Channel SANs are security of storage data as it traverses the network and quality of service to ensure proper delivery. Chapter 10 reviews mainstream IP security features that can be used for IP storage networks, whereas Chapter 11 examines class-of-service and quality-of-service standards and standards initiatives. These chapters validate in principle the marketing claims of IP storage vendors that IP SANs may leverage the advanced functionality already deployed for enterprise IP networks.
Although IP storage networking is generally viewed as the successor to Fibre Channel, InfiniBand has also been promoted as a homogeneous solution for everything data related. Chapter 12 provides an overview of the InfiniBand architecture and how it may integrate into IP storage solutions.
Technology development would have little purpose if it did not solve real customer problems. Chapter 13, therefore, offers application studies to demonstrate how IP storage solutions may be applied, including server cluster, storage consolidation, LAN-free and server-free tape backup, and metropolitan and wide area applications for SANs. In many respects, a diagram of an IP SAN solution for a specific application may not differ significantly from a comparable Fibre Channel SAN solution. Boxes reside in the middle, lines are drawn, boxes sit at the end. The substantive difference, however, is how easy those boxes are to acquire, deploy, manage, and maintain. In the end, the customer does not and should not have to worry about the underlying plumbing. The customer simply expects to turn on the spigot and for data to appear. If that is convenienced by IP SANs, then the mission of IP storage vendors is accomplished.
Lastly, Chapter 14 discusses new technologies in general and the inflated expectations that invariably accompany them, and then reviews the fundamental prerequisites that must be met for successful adoption of IP storage networking. IP storage has the potential to alter traditional concepts of data access at a much more fundamental level than previously viewed via Fibre Channel SANs. If IP storage is successful, storage-specific issues may gradually disappear as networked storage access becomes more ubiquitous.