Interview with Gregory Pfister

Reading Gregory Pfister's In Search of Clusters and then talking to Wolfpack participants intrigued me with the person who brought together and explained the ideas necessary to implement clustering. I wondered whether he was aware of the impact of his book and what he thought about how vendors where putting his concepts into practice. The following interview resulted from my interest in this book and its author.

Q: Are you aware that the name Wolfpack is based on your book?

Yes, Microsoft sent me a T-shirt and a letter letting me know that Clusters influenced the name.

Q: When you subtitled your book, The Coming Battle in Lowly Parallel Computing, what did you have in mind?

I was thinking of clusters of commodity PCs vs. large SMP systems (12-, 16-, 32-way). The battle lines are just now being drawn.

Q: Do you see a large market even for Wolfpack Phase 1? Is it possible to see a tenfold increase in the quantity of clusters shipped in the next year?

It's possible, but many vendors will have to participate before clusters reach critical mass. Can one large vendor accelerate the process? Absolutely.

Q: How does Intel's four-way Pentium Pro take advantage of NT's SMP capabilities?

Going to the Pentium Pro, Intel made several changes that significantly increase the bus capabilities, which is the key limiting factor in SMP. So SMPs made with the Intel bus and the Pentium Pro chipset will be a lot better than SMPs made from Pentium chip set. They will be formidable machines.

Q: Will four-way clusters provide a better price/performance point than large (8, 16, 32 CPUs) SMP boxes?

Large SMPs cost more to produce than clusters of small SMP boxes and will therefore be more expensive. However, until cluster vendors provide a single-system image of the cluster, a large SMP will be easier to administer than a cluster.

Q: As we move toward scaling clusters, will message passing between nodes become more important?

The Message Passing Interface (MPI) is an existing standard that would help this effort, but I imagine Microsoft will adopt its own proprietary solution, Distributed Component Object Model (DCOM).

Q: What are the challenges that face Wolfpack as it moves toward scaling clusters?

The single-system image will be a huge problem to overcome. Will NT support a clustered file system to let a user view a set of files that are the sum of all nodes in the cluster? Will communication from outside the cluster have to know the address of an individual node, or will a message be able to point to a cluster? Will network management systems see the cluster as a single element or as multiple separate computers? A whole lot of these services will have to be available before an administrator will say that a cluster appears as a single computing resource in the same way a large parallel system appears. The company that provides that stuff first and on the best price/performance hardware will be a winner.

Q: Is everything coming together now that will let clustering become commonplace?

Possibly. There's no new technology necessary to do this. The technology exists. What's necessary is the will and the vision to do it.

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