Can NUMA hit the server big time?

The state of NUMA Who's got it, who's thinking about it and who might get it.
Vendor	NUMA position
Data General	Offers Aviion NUMA servers
Sequent	Offers line of NUMA Q-2000 servers
Compaq, Dell	No interest at this time
HP	Offers two NUMA Exemplar and V class servers
Amdahl	Considering NUMA design in M8001 server
IBM	Evaluating NUMA for Netfinity

The life of NUMA server users and vendors can be lonely.

Non-Uniform Memory Access (NUMA) is a symmetrical multiprocessing (SMP) technology most fervently backed by companies such as Data General and Sequent, which claim NUMA overcomes the performance limitations of traditional SMP systems.

But to date, the technology has been rejected by big name server vendors, such as Compaq and Dell, and software vendors, such as Microsoft. Will NUMA catch on in a bigger way in months to come? There are some indications that it could. For example, IBM is giving the technology serious consideration. But most evidence points to the technology continuing to lurk in the shadows.

NUMA proponents claim the technology is an improvement over traditional Intel-based SMP systems that can suffer from traffic jams on their shared-memory buses and typically cannot accommodate more than 16 or 32 processors. With NUMA, each Intel processor has its own local memory and is able to form static or dynamic connections with other chips' memories. NUMA servers can be powered by 64 or more processors.

"NUMA is at the beginning," says Steve Aucoin, director of product marketing at the Aviion business unit at Data General. The company estimates that about half its server revenue comes from NUMA unit sales. "Over the next couple of years, you'll see more major vendors getting NUMA products out there," he says.

Data General and Sequent have been selling NUMA servers for more than a year, and Hewlett-Packard and Silicon Graphics sell NUMA machines to handle certain technical applications. But it is tough to get a handle on the size of the market because vendors don't break out their NUMA sales figures.

However, according to anecdotal evidence, it appears that NUMA systems are working as advertised. "The Aviion 20000 doesn't go down at all . . . NUMA has proven to be a very sound concept," says Peter Clark, manager of information systems at Jordan's Furniture, an Avon, Mass., retailer that has been using an eight-processor Data General NUMA server for about a year. Clarks says he is particularly enamored with the Pentium Pro-based server's ability to balance loads across processors. Previously, Jordan's used a 12-way Data General Aviion 9500, a system that could no longer handle the company's point-of-sale and other applications.

Pricing for Data General's NUMA boxes starts at less than $80,000 for a four-way server, which the company claims can be one-third to one-half of the price of enterprise servers from other companies.

NUMA should prove most attractive to companies running online transaction processing, enterprise resource planning and other processing intensive applications, says Richard Partridge, an analyst with D.H. Brown Associates, a Port Chester, N.Y., market research and consulting firm. He expects more vendors to get into the market once Data General and Sequent work out any kinks in the technology.

One of those vendors could be IBM, which is giving NUMA some serious consideration as a future architecture for its Netfinity line of PC servers, says Tom Bradicich, director of server architecture and technology at IBM's personal computer group. He sees a possible role for NUMA in certain server cluster systems.

HP offers NUMA servers through its Convex division. For example, the company offers the Exemplar server for running technical applications and the V Class box for commercial applications. HP is trying to keep an open mind about whether NUMA will play a bigger role in its server products down the road, company officials say.

"We don't take a particular religious position on any of these things," says Brian Cox, a product manager for HP's NetServer division. He says the company's decision to support NUMA more widely would hinge on such factors as SCO's UnixWare or Microsoft's Windows NT gaining NUMA hooks.

Dell is more skeptical. As Microsoft and Intel improve their operating system software and processors, respectively, the need for NUMA will drop off, says Bob van Steenberg, vice president and general manager of Dell's enterprise server division. In three years, SMP performance in NT boxes will exceed that of NUMA machines, he says. "We don't want to go backwards," van Steenberg says.

Compaq has evaluated NUMA for the past two or three years and has paid particular attention to where application vendors are going, says Karl Walker, vice president of technology development at Compaq. "We want to make sure we provide platforms that are consistent with where the majority of the systems and software base is going," he says. "NUMA has some positives. But it has some attributes that we think are not appropriate for a lot of mainstream deployment. We see it as useful more in specialized, highly scientific applications."

Like Dell, Compaq is putting much of its efforts into supporting a message-passing server communications technology called Virtual Interface Architecture (VIA), which Microsoft is supporting. "With VIA, a message can be sent from any processor to any processor regardless of the memory architecture," Walker says. "NUMA architectures are more tightly coupled to the specific memory architecture of a specific CPU and don't lend themselves as well to heterogeneous environments."

Sun says it's doing just fine with its SPARC-based SMP servers running Solaris. "The fallacy is that you cannot engineer large SMP systems when in fact you can, and we have been for the past two years, as evidenced by our 64-CPU offerings," says Ken Won, future systems marketing manager for Sun.

Despite what vendors say, some observers believe that many Unix server vendors are going to slip some form of NUMA technology under the covers of their machines, though they may not necessarily call attention to it.

"In five years, all the players will have this engineering approach in their platforms," Partridge predicts.

NUMA architectures and user level scheduling - a short introduction

AV 20000 and ccNUMA: Beyond The Application Bottleneck
Data General white paper.

Non-Uniform Memory Access Hardware: A Primer
Compares NUMA to other approaches.