In-Depth

Multi-Core Enterprise Computing: A Ferrari Engine in a Go-Cart

Chip densities are doubling every 24 months, but a new report says few applications can take advantage of the change.

• By Stephen Swoyer
• 02/03/2009

Proponents like to point to the increasing density of commodity servers -- with quad-core systems common, eight-core chips on tap, and 16- and 32-core chips shipping, and even bigger chips on the drawing board -- as proof that pervasive virtualization is inevitable. At first glance, a new report from Gartner Inc. seems to put that enthusiasm in check, chiefly by suggesting that organizations will have trouble effectually using all of those chip cores. To a degree, however, the Gartner report further bolsters the virtualizer's case: existing software just isn't able to scale across SMP chip configurations of the kind that are being dveloped.

"Looking at the specifications for these software products, it is clear that many will be challenged to support the hardware configurations possible today and those that will be accelerating in the future," said Carl Claunch, vice president and distinguished analyst at Gartner, in a statement. "The impact is akin to putting a Ferrari engine in a go-cart; the power may be there, but design mismatches severely limit the ability to exploit it."

With so many chip cores idling inside of comparatively few servers -- and with most of these systems having been physically consolidated into highly dense rack configurations -- virtualization provides the single best way for IT organizations to both ratchet up system utilization and manage hundreds or thousands of virtual engines. On the other hand, skyrocketing chip density is already close to overwhelming most of today's top virtualization technologies, Gartner points out. At current rates, on-chip core configurations double every two years.

One upshot of this, Claunch says, is that a 32-way server can accommodate as many as 256 chip cores -- when outfitted with eight-core microprocessors, that is. By 2011, the same server -- still with a base 32-way configuration -- will accommodate 512 chip cores; and by 2015, Gartner projects, that number could double again, this time to 1024.

"Most virtualization software today cannot use all 64 processors, much less the 1,024 of the high-end box, and database software, middleware, and applications all have their own limits on scalability," Claunch explained. "There is a real risk that organizations will not be able to use all the processors that are thrust on them in only a few years time."

How will today's technologies run out of gas? Claunch says it's a question of "hard" and "soft" limits, with the former hard-coded into the virtualization, operating system, or application software itself. For example, an operating system could use an eight-bit field to store its processor configuration, which sets an effective hard-limit at 256 processors.

So-called soft limits, on the other hand, are altogether more insidious. "Soft limits, however, are uncovered only from word of mouth, real-world cases. They are caused by the characteristics of the software design, which may deliver poor incremental performance or, in many cases, yield a decrease in useful work as more processors are added," the Gartner statement reads.

The lesson for buyers, Claunch and Gartner conclude, is to both be vigilant and to temper one's enthusiasm for highly dense server configurations -- at least until one can do one's homework.

"There is little doubt that multicore microprocessor architectures are doubling the number of processors per server, which in theory opens up tremendous new processing power," Claunch concludes. "However, while hard limits are readily apparent, soft limits on the number of processors that server software can handle are learned only through trial and error, creating challenges for IT leaders. The net result will be hurried migrations to new operating systems in a race to help the software keep up with the processing power available on tomorrow's servers."