A Cluster by Any Other Name Is Not a Grid

Have you noticed how lately, when the conversation turns to distributed computing, grid and cluster are used as synonyms? These two words do have different meanings, Donald Becker reminds us.

“Clustering takes multiple independent machines, and through software and networking, makes them appear as a single, more powerful and/or reliable machine,” Becker says. “What you are trying to do is to create a unified virtual system over multiple single machines. Grid is a concept that involves working with a large number of separately administered machines. With grid, you don’t control the configuration, the operating systems, the libraries installed—anything. So it’s a lot more difficult to ensure that that application is going to run remotely.”

So-called grid computing solutions for small to midsize businesses are more likely to be utility computing or clustering solutions, Becker says. A grid implementation is much more difficult. The only place for "true grid," he says, is with global enterprises that have a single point of administration for the CIO.

Becker knows whereof he speaks. While working at NASA's Goddard Space Flight Center during the late 1980s, Becker created the first Beowulf cluster, using software to connect many inexpensive PCs to solve complex math problems typically reserved for classic supercomputers.

Beowulf is a trademark controlled by Linux International. It defines a type of scalable performance cluster based on commodity hardware, open-source infrastructure software and a private system network.

Becker founded Scyld Computing in 1998 to design a new generation of cluster control software. He now serves as the company's chief scientist. Scyld, which is a subsidiary of Penguin Computing, develops and sells a cluster operating system called the Scyld Beowulf Series 29 Linux Clustering Software. Better known as Scyld Beowulf, the platform is a standards-based Linux distribution that has been extended through the Scyld BeoMaster technology for ease of deployment and manageability of Linux clusters. A full high-performance computing software toolset is integrated with the platform, and it utilizes the Linux Kernel Version 2.4. Most MPI applications running on Red Hat Enterprise Linux ES 3 run unchanged in the Scyld Beowulf environment, Becker says.

One of the keys to the success of his company’s technology, Becker says, is the open-source infrastructure on which it runs. "We have some new ideas on how to make large sets of machines very simple to manage," he says. “But without an open-source infrastructure such as Linux, we wouldn’t be able to do that.”

Becker finds it "curious" that grid and cluster have become almost interchangeable terms. "A few years ago, clusters meant simple one-to-one failover," he says. "The terms have moved from that simple concept of a single spare taking over a workload to being synonymous with chains spread across the planet. It’s surprising.”

Becker literally wrote—or rather co-wrote—the book on Beowulf Clustering: How to Build a Beowulf: A Guide to the Implementation and Application of PC Clusters (with Thomas Sterling, John Salmon, and Daniel F. Savarese, The MIT Press, May 28, 1999).

About the Author

John K. Waters is a freelance writer based in Silicon Valley. He can be reached at


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