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  Book Review

iSCSI: The Universal Storage Connection
Book author: John L. Hufferd

Copyright © 2003 by Pearson Education, Inc


When this book appeared, I was happy to see that John Hufferd of Brocade (formerly of IBM) had written the first tome on the topic of the iSCSI storage protocol.  I have heard John speak at storage conferences, and have listened to the questions and comments he has posed and offered to other conference speakers.  I have also read many an email he has written related to iSCSI and similar topics.  He is clearly a true authority on the topic of iSCSI.  To understand this protocol requires a good understanding of both storage and networking technology, and John is one of those people who truly straddles the fence.

His book has an excellent organizational style.  Each chapter begins with a brief “To the Reader” section, and ends with a Summary.  The last chapter is a summary and set of conclusions about the material addressed in the book, and even includes a summary of those conclusions.  As would be expected for a book about a computer standard, the last third of the book is a set of appendices.

This book will invariably be used as a reference tool, with the index serving as a guide.  However, this book also includes “To the Reader” sections at the start of each chapter that are helpful in finding the chapters that are of greatest interest to many readers.  Thus, a non-technical marketing person could skip a lot of the gory details, and a software or hardware engineer could get the level of detail appropriate for an engineering project.

Intermixed with the details of the standard is a perspective into the networking and the storage aspects of the standard that are critical in allowing this storage protocol to operate in the real world of the Internet, i.e., to operate as a hybrid protocol.  These include some history and working details of TCP/IP Offload Engines (TOEs) and Remote DMA (RDMA), both of which are important for efficient implementations of iSCSI.

I found the historical anecdotes lent a perspective to understanding how we got where we are today with the standard, as well as with TOEs and RDMA that are so important to the real world’s use of iSCSI.  One of these was from 1999 when some TCP/IP and NIC vendors said that a TOE on a chip was not possible or reasonable.  This was most interesting when Broadcom announced C-NIC in 2004, which integrated iSCSI, TOE and RDMA on a single chip.  C-NIC also allows booting from a server, and hence has led directly to stateless blades – this is the true separation of storage from server blades.

While storage environments have been generally deterministic, iSCSI changed this dramatically when it allowed the commands and data involved in storage access to be placed in the highly non-deterministic environment that is the Internet.  Insights into the ramifications of this change are included in the material presented in Hufferd’s book.  For example, Chapter 9 is titled “Structure of iSCSI and Relationship to SCSI.”  This chapter shows how the framework presented in the preceding chapters works with concepts that are integral to the SCSI standard at the logical level, e.g., initiator, target, nexus and persistent reservation.  Just as SCSI is at the heart of the Fibre Channel and IDE/ATA storage standards, this chapter shows how SCSI works in the networking context of iSCSI.

Hufferd is quick to send the reader to the actual Internet Engineering Task Force (IETF) spec if questions arise or if clarifications are necessary.  Indeed, the book came out when Draft 18 was the latest version, and the work on the iSCSI standard did not finish until Draft 20 was completed in February 2003.  However, all the heavy lifting for iSCSI had been completed by the time this book was written.

Hufferd notes that iSCSI was initially developed at IBM Research, and that collaboration between IBM and Cisco brought it to the IETF.  As Technical Coordinator for the iSCSI track of the IETF standards committee, he was the right person in the right place to coordinate all the work that went into making the iSCSI standard come to fruition.

The book opens with credits to the many folks who have been involved with creating iSCSI, a standard that was first known as “SCSI over TCP/IP” in early 2000.  By early 2003, the standard reached a milestone with IETF, and Microsoft released an iSCSI driver in the summer of 2003.  iSCSI had arrived.

Some books have the feel of being tacked together, with chapters being haphazardly constructed.  This one was engineered – information is presented in a highly organized and logical fashion.  Consider it the starting point for an understanding of this protocol.

Brian A. Berg
Berg Software Design

Brian Berg is an independent consultant specializing in storage devices and storage interfaces, including work with patents and intellectual property.  He maintains a Storage Cornucopia of storage-related links on his website