As a result, grid has become a centerpiece of the "utility computing" marketing drive taken up by nearly every vendor. Load balancers, clustering solutions, blade servers?just about any product can come to market with a grid label. But that hype doesn’t mean it’s grid.

"When I first started covering grids two and a half years ago, Sun had defined grids as including clusters," says Joe Clabby, president of technology research company Clabby Analytics and author of a recent report on the state of grid. By that definition, Sun would have had more than 5,000 grids. But while grids and clustering both share resources across multiple machines, grids, according to Clabby, are different because they allow "distributed resource management of heterogeneous systems." In other words, with grids you can quickly add and subtract systems?without regard for location, operating system or normal purpose?as needs dictate. Clusters are built from the ground up to function as a single pool of compute power and consequently aren’t as flexible.

The Scale’s the Thing

Scaling is one of grid’s primary benefits to the enterprise. With properly designed grid-enabled applications, grid can produce staggering performance improvements?add a new processor and get that processor’s full power added to the mix. Using grid math, you can add two or more cheaper, slower processors to achieve far greater power than you could with a much more expensive high-end machine. String enough processors together, you can even exceed the number-crunching power of some supercomputers.

Scalability at an affordable price was the key to grid for Acxiom, a company that specializes in cleaning and integrating customer data. Acxiom, for example, can determine if Bob A. Smith and R. Albert Smith in Los Angeles are the same person and, if so, consolidate his customer data into a single record. This is a critical task for marketers looking to maximize the effectiveness of their campaigns, but it takes massive amounts of processing power.

Acxiom’s "link append engine," called AbiliTec, takes name and address information and uses it to create links to databases, and it does this a lot: 15,000 links every second, 24/7, according to C. Alex Dietz, products leader at Acxiom. "It’s a perfect application for grid computing," Dietz says. "Take one name and address and feed it to the appropriate grid node. In parallel, feed the next name and address to another grid node."

But when Acxiom started integrating AbiliTec into all of its services, the company discovered that the original architecture?based on multi-CPU symmetric multiprocessing machines?wouldn’t scale sufficiently to handle the load. Acxiom then built the grid system from scratch using custom code (built around Ascential Software’s Orchestrate framework for grid applications) and a bank of IBM blade servers that supply some 4,000 nodes for the grid. (For more on blade servers, see "The Inevitability of Blade" on Page 68.) The result has been the capacity to process 50 billion records a month. "We had to invent a way to take a raw name and address and go into a database and extract links extremely fast and extremely accurately," says Dietz. "We couldn’t do it with traditional techniques."