In Search of Clusters (2nd Edition)

From the Publisher:

This provocative new book explains an increasingly popular form of parallel or distributed computing that is frequently misunderstood. A leading expert on multiprocessing, Pfister demonstrates that clusters are a distinct form of parallel computing with extraordinary potential and highlights the critical role clusters can play in downsizing.

From the Inside Flap:

Preface to the Second Edition

Well, I had to write a second edition. Too much of what I predicted in the first edition became history. You know, it feels good to be able to say that. They even code-named the development project at Microsoft “Wolfpack” after the cover. “Dogpack” or “dogfight” didn't have the right connotations, I guess. Sent me a logo T-shirt, too. I also got some nice e-mail from other developers, but nobody else was that classy. Before I completely dislocate my shoulder patting myself on the back, I should mention that I missed a couple of rather major things the first time around. I didn't foresee the importance of mass-market high availability. I also didn't foresee how much confusing “NUMA” rhetoric would be used. Neither were left out entirely, mind you, but they certainly didn't get anywhere near the attention they either deserve or require. That's been corrected, in the form of two major added chapters, major revisions to other chapters, and scattered revisions throughout the book.

Another major change is the inclusion of information about cluster hardware and software acceleration, a subject that literally did not exist in sufficient quantity to take notice of when the first edition was written. Of course the chapter of examples was trash about 40 seconds before the first edition hit the stands. This edition's version probably will be, too. There has to be a better way to do that part; books can't compete with magazines' rates of publication, much less the Internet. I've tried to be more generic in this edition, but you can't ignore the real systems and do that job right.

However, the basic original structure of the book has stood up adequately, for which I'm grateful; this edition would have been far more work were that not true. As a result, readers of the first edition will probably have an odd sense of reverse deja vu (jamais vu?), like “Hey, I thought I read that before, but it didn't say that.” Believe me, literally every page of this thing has been changed. Why? When the first edition was written, it really was true that most people in the computer industry had not heard of clusters, and those that had mostly considered them a lower form of life. Products that really were clusters weren't called that, because there were much cooler things to claim to be: Massively Parallel. Distributed. Hemidemisemicoupled. Whatever.

Now you would have to be deaf to not have heard of clusters. All God's chilluns got a cluster product, or two, or four, and are talking about them'if that's the phrase'with all the power of their collective lungs. The products are mostly (not always) fairly crude, but, hey, you have to start somewhere. At least they recognize the name. I've had to revise things fairly pervasively to take this new milieu into account, and have also removed some of the ranting about how this might actually be a useful thing to do. Not all. Some.

I'd like to think that the publication of the first edition had something to do with this change in the state of affairs. That would be far more satisfying than merely having correctly nailed a few short-term predictions.
Acknowledgments

I of course remain grateful for IBM's rather enlightened policy towards book authors, which still provides both support for writing and motivation to complete the job. The views expressed here are not necessarily those of the IBM Corporation, of course.

I am also again grateful for the support of my family, who once again put up with my lack of attention while immersed in this project, even though the first edition didn't produce all its promised benefits: my children Danielle and Jonathan, and, of course, my wife, Cyndee Stines Pfister'who originally said that was probably her only chance to get her name in a book. Well, lightning strikes twice.

I also again owe a large debt to the many people who have discussed the subjects of this book with me, both within and outside IBM. I feel privileged to say that the clich remains true: There are far too many to mention all of them individually. However, my manager, IBM Fellow and Vice President Rick Baum, must certainly be thanked for uttering the fateful words, “Don't you think it's time for you to do a second edition?” And then giving me the time to actually do it'possibly more time than he anticipated, and certainly more than I originally estimated, but it did finally get done. Jim Rymarczyk, Dave Elko, and Pete Sargent at least partly repaired my woeful ignorance of Parallel Sysplex. I'm particularly grateful to Dave for the several sessions at which he endured my intemperate questioning. Tom Weaver and Lisa Spainhower provided extremely useful review feedback, as well as much useful discussion over the years. Renato Recio, Tom Chen, Jeff Weiner, and other members of the System Architecture and Performance I/O team are also to be thanked for the times when, hiding behind the clever fa ade of “we're just dorky I/O guys who don't know nothing about the serious stuff,” they filled in large gaps in my understanding of that Rodney Dangerfield of computing. Not all the gaps, by any means; but I'm better off than I was before. And Bill (“Rocky” ) Rockefeller: May he always keep The System off all our backs.

Once again, however, the people who are most to be thanked are the IBM customers I have met over the years, as well as the members of the IBM field force who brought us together. Those customers gave me the opportunity to find out what was really of importance to them, which of course must be of paramount importance to we who serve them. It appears that many of them really do want to understand the kind of information that is in this book'at least when it is properly explained, as I have tried to do. They also unwittingly provided me with numerous opportunities to try out ways of explaining various topics, and to debug the analogies, metaphors, and jokes in response to questions and quizzical looks. As a direct result, getting through many of the chapters that follow will require markedly less caffeine.
Greg Pfister
August, 1997
Austin, Texas
pfister@us.ibm
Preface

Anyone planning to purchase, sell, design, or administer a server or multiuser computer system should buy and read this book.

Key needs of those systems'high performance, an ability to grow, high availability, appropriate cost, and so on'imply the use of parallel processing: multiple computing elements used together as a single entity. Parallel processing, with a bit of distributed processing, is what this book is about; it will give you the background needed to understand where the real issues lie in that realm. However, this doesn't mean that this book discusses “highly” or “massively” parallel computers. Those are flamboyant enough to have already attracted a multitude of variably successful explanations and are really of direct interest only in a vanishingly small fraction of the computer market.

Instead, this book uniquely discusses both the hardware and the software of “lowly” parallel computers, the everyday, practical work gangs of computing: symmetric multiprocessors, so-called “NUMA” systems, and, in particular, clusters of computers.

You do not have to be a died-in-the-denim “techie” to enjoy and profit from this book. Its form and content reflect the author's experience in explaining these issues quite literally hundreds of times to people with at best a semi-technical computer background. This has included customers who have better things to do with their time than become computer technophiles; marketing reps, both the technically oriented and the Jag-driving backslappers; and development managers, who too often think they have better things to do with their time than understand the technological basis of their business. You do need familiarity with the current computing milieu. An ability to (mostly) understand the thick, monthly computer magazines demonstrates a background adequate to get a lot out of this book. In some areas this may even be overkill. If you've understood this preface so far, you're in good shape. But that this book has been written to be accessible does not mean that it is Ye Compleate Moron's Guide to a Child's Garden of Stupid Tiny BASIC Tricks, either. Its content is not technically trivial. Because it approaches both parallel and distributed systems from a nonstandard viewpoint, that of clusters, it offers a fresh perspective that can potentially enrich both. As discussed below in “History,” technically sophisticated readers have profited from prior versions that weren't publicly published. Of particular interest have been the analysis of single system image and the characterization of the programming models used in commercial computing.

One result of this unusual perspective is that while many different groups of peo

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