IBM's mainframe makeover

For the past several years, Big Blue has transferred the technology inside its mainframes to beef up its other server lines. Now the process is going the other way.

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Stephen Shankland
7 min read
For the past several years, IBM has transferred the technology inside its mainframes to beef up its other server lines. Now the process is going the other way.

The Armonk, N.Y.-based computing giant has kicked off a project to dramatically change the underlying architecture of its zSeries mainframes so the machines will use the same Power processors and other technology as its high-end, but less expensive, pSeries and iSeries servers.

By using the same processors across product lines, IBM will potentially be able to substantially reduce the cost and time involved in bringing mainframes to market, as well as cutting the cost of supporting them once they get installed in corporations. Currently, IBM has four server lines, each with its own software and engineering teams. The company will also likely be able to consolidate software development.

"For the first time, IBM will have converged three of its four servers onto a common hardware platform," an IBM executive wrote in a document reviewed by CNET News.com.

The memo also stated that IBM is working to adopt the InfiniBand high-speed networking technology across all three of these server lines as well as its line of Intel-based servers, which would further simplify product development and support.

IBM declined to comment on the strategy, but analysts viewed it with cautious praise as a way to cut hardware and software engineering costs.

"As a long-term plan, it does probably make some sense," said Illuminata analyst Jonathan Eunice, but engineering challenges and a demanding customer base make the task difficult.

Mainframes--highly regarded for their imperviousness to problems as severe as central processor failure--ship with highly customized software and different memory and communication subsystems than those found in most servers. Their ability to process huge numbers of transactions per second makes them widely used for tasks such as managing sales inventory or tracking bank accounts.

Big Blue's server family
Quick guide to the IBM server world

zSeries: Formerly the S/390. Top-end mainframes with entrenched corporate customer base. Sell often for more than $1 million. Run the z/OS, VM and Linux.

iSeries: Formerly the AS/400. Mini-mainframes running AIX and Linux. Loyal following. Power processors inside.

pSeries: Formerly the RS/6000. Linux-Unix server for general business. Runs on power chips.

xSeries: Formerly Netfinity. Intel-based servers running Windows and Linux. Often least expensive, least powerful machines but gaining power and popularity.

But the million-dollar-plus systems are expensive, especially when software and support costs are factored in. Competitors such as Sun Microsystems and Hewlett-Packard have been trying to beckon mainframe buyers with Unix servers.

Because of their customized nature, change moves at a glacial pace in the mainframe world. Incorporating the Power processor line into the zSeries, for instance, is more complicated than just writing a software layer that would emulate the old processor and allow the use of existing software.

But IBM has the ability to execute a multiyear project and make such a change without disrupting customers. "IBM doesn't think in normal terms. Their planning horizons are very long-term," said Kevin Krewell, an editor with the Microprocessor Report, an online newsletter.

Among IBM's recent successful projects was a years-long effort to catch up to Sun in Unix servers and its X Architecture plan to lift Intel servers past some of their current limitations.

The processors in today's mainframe are a "pretty old design," Krewell said, and changing to Power chips would allow Big Blue to take advantage of more modern features such as "superscalar" processing, the ability to carry out several operations simultaneously.

The shift to Power architecture isn't expected soon--most likely some time after the appearance of the Power6 processor planned for 2006, one source familiar with the plan said. It took years for IBM to shift its mainframes from its earlier 31-bit processors to the current 64-bit line introduced in 2000 with the z900.

Dramatic steps
The move was foreshadowed by IBM's decision in 2000 to consolidate its four server lines under the eServer brand. The company has been working to share technology and research across the four lines, but bringing the Power processors to the mainframe would be one of the most dramatic steps to date.

IBM already has trumpeted its efforts to bring mainframe capabilities to the rest of its server line. Ravi Arimilli, chief technology officer for IBM's Power line, boasted in a recent interview that IBM's coming Power5 processor was "95 to 97 percent" of the way toward a mainframe processor, and said some of IBM's Power chip design "is a reflection of what IBM" accomplishes in mainframes.

And convergence has already begun elsewhere among IBM's servers that share the Power processors.

The Power processors are 64-bit chips that are related to the 32-bit PowerPC processors used by Apple Computer or in networking equipment made by various manufacturers. The 64-bit chips, though, are more powerful and versatile. The chips can manage far larger amounts of memory, which in turn allows servers to access information from databases much more quickly.

IBM first started using the 64-bit Power chips in 1995 in its AS/400 systems--now called the iSeries line. In 1997, it brought the Power chips to its pSeries Unix servers.

Until recently, the iSeries and pSeries used somewhat different Power chips, but that's changed with the introduction of the Power4 chip in the top-end p690 "Regatta" and the i890 machines. Though the processor is the same, there are some other hardware differences between the p690 and i890.

Those refrigerator-size systems also share some parts with the mainframes, including the cabinet, power supplies and internal frame. "We're bringing about convergence where it makes sense. Where it is practical, we're leveraging common technology across the different series platforms," Mark Shearer, vice president of eServer product marketing, said in an earlier interview.

Software convergence
Software is another area where convergence is possible. The iSeries can run Linux and its native operating system, OS/400, but IBM announced in April that an update will let the iSeries servers also run AIX, the version of Unix that runs on IBM's pSeries servers.

Merging iSeries and pSeries has allowed IBM to pool research from the Rochester, Minn., iSeries team and the Austin, Texas, pSeries team. For example, the two lines share some of the same "hypervisor" software, which runs at a lower level than the operating system.

Hypervisor controls tasks such as adding new processors to a server as it runs or managing how resources are shared among independent "partitions" on a server--sections of the server that more or less act as independent servers.

IBM is also looking at interweaving zSeries trends more tightly with hypervisor advances, Helene Armitage, IBM's vice president of Unix software development, said in an interview.

Hypervisor is becoming more significant as Big Blue works on programs such as its eLiza effort to make servers self-healing, Armitage said. IBM wants hypervisor to perform error detection and correction functions, fixing problems before they have time to distress the operating system, thereby making newer operating systems such as Linux more reliable. And IBM is "looking at" embedding hypervisor functions directly into the Power processor.

Another aspect of software convergence is through Linux, the Unix-like operating system IBM supports across all four of its server lines.

Competitive pressure
IBM's mainframes are well ahead of Unix and Windows servers in their abilities to continue running under almost any circumstances. Cosmic rays? The zSeries isn't affected, unlike some Unix offerings. But competition is increasing.

Sun has publicly said it looks to mainframes for inspiration when designing its high-end Unix servers. And Hewlett-Packard is seeing strong sales of its top-end Unix server, with sales increasing 5 percent in the quarter ended April 30 and revenue from future orders surging 33 percent.

Both those companies are consolidating development as well. Sun's "Uniboard" strategy recycles processor modules (a board-like structure that includes processors and memory) across its higher-end servers, simplifying development and testing.

HP, after its acquisition of Compaq Computer, has four processors in its high-end servers, but is working to shift them all to Itanium, a chip it co-developed with Intel, by 2004.

Some competitive pressures have eased, though. Hitachi and Fujitsu's Amdahl subsidiary withdrew from the mainframe market, said Toni Sacconaghi, an analyst with brokerage Sanford C. Bernstein.

Mainframe revenue in 2001 at IBM increased for the first time in six years because of the resulting "benign pricing," Sacconaghi said. While the sales of mainframe processing power grew in line with historical averages, the pricing for that capacity dipped 12 percent instead of the 30 percent average of the previous five years, he said.

Switching mainframes to Power processors is a good idea, Sacconaghi added. "From an economic perspective, it makes sense. The trick is providing seamless transitions on the software side," he said.

Still years away
Mainframe processors have sophistication the Power series will have to match before the switch is made.

For example, mainframe processors essentially have two processor "cores" that simultaneously execute the same instructions, the Microprocessor Report's Krewell said. If the cores come up with different results, they automatically redo the calculation, repeatedly if necessary, and if the results still are different, the processor hands over its duties to a different processor.

A processor can say, in effect, "'I suffered a failure, but don't worry, I moved that instruction over to that other processor,'" Illuminata's Eunice said.

"That's the kind of thing that causes Unix or Windows to panic," Eunice added. "It's pretty hard to do what a zSeries does. If it weren't, every Dell, HP and Sun box would do it."

Switching processors is tough, but IBM has experience at the job. For example, it switched its AS/400 line to the Power architecture without losing its loyal customer base.

HP's NonStop division, the makers of the high-end line formerly named Tandem, has switched more than once, Eunice said, and Intel has retrofitted Pentium chips so the old instruction language still works but the inner workings are more modern.

"At some point it becomes mandatory (to overhaul processors) because...plowing big money into moving the older design forward is prohibitive," Eunice said.