Exclusive: IBM deals a pair of powerhouses

With its new eServer OpenPower 710 and eServer p5 510, IBM has delivered two state-of-the-art enterprise servers that can handle transactions galore. And these products sport what is probably the industry's most advanced microprocessor for server consolidation, fault-tolerant apps, and floating-point-intensive computation.

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Well, strictly speaking, there really is just one server. The two boxes are exactly the same, with the only discernible difference being a firmware limitation on one of them that prevents it from running anything but Linux.

You may have seen that IBM has been hyping its OpenPower product line as "Tuned for Linux." That's what I saw in the company's literature, and that's what I heard from product managers who briefed me on the servers during the review process. Try as I might, however, I could find no difference in these two 2U (3.5-inch), dual-Power5 servers, other than that the OpenPower 710 was running Suse Linux 7.0 and that the p5 510 was running AIX 5L, which is IBM's version of AT&T Unix.

Finally, an IBM engineer gave me the skinny. The phrase "Tuned for Linux" refers to OpenPower's marketing position. "They're the same boxes coming down the assembly line," he said.

But there are two, and exactly two, differences: One, the OpenPower 710 has a significantly lower price, which is meant to help IBM gain traction in the Linux market with the Power5 processor; and two, there's a firmware block that prevents an OpenPower box from booting anything but Linux, a feature meant to keep the box from cannibalizing sales of the p5 server to the AIX crowd.

With that in mind, I took a look at the servers to see what makes them tick.

Cache is king

These servers sport three key differentiators when compared with other RISC-based systems on the market: their dual-core Power5 processors with 1.9MB of L2 cache and 36MB of L3 cache; hardware-based partitioning; and high-end fault-tolerant features.

The Power5 processor, which is an evolution of the old PowerPC series, is a RISC processor that's well suited to floating-point processing. In its earliest incarnation -- in IBM's RS/6000 workstations -- it found a home in scientific and visualization applications. The Power5 continues to be a strong floating-point system, as the 1.65GHz processors in the OpenPower 710 and p5 510 are incredibly fast. Although I didn't run formal benchmarks, it was blazing when I ran BLAS (Basic Linear Algebra Subroutines) applications on the Linux system. The systems I tested had 4GB RAM. They are expandable to 32GB.

This incarnation of the Power5 processor also has dual cores, so the two-processor servers can run four threads in hardware simultaneously. So far the only other dual-core RISC processor is Sun's UltraSparc IV chip; the two are essentially equivalent in performance, but the Power5's extra cache makes it better suited not only to numerical work but also to heavy-duty multiprocessing, as would happen in a server-consolidation scenario. Cache truly is king.

Partitioning -- in the IBM world, it's called LPARS, or Logical Partitions -- allows a single computer to behave as if it were many different computers. Application and OS states are maintained separately in each partition. This is ideal for server consolidation.

Unlike software-based partitioning, such as VMWare or Microsoft's Virtual PC, however, a common OS image can be shared among partitions, making this very efficient. LPARS are a common feature of IBM's zSeries mainframes and iSeries minicomputers. Although Sun offers a similar feature, called containers, as part of Solaris 10, IBM has implemented partitioning in the servers' firmware.

The practical benefit of hardware-based partitioning is that LPARS can, if desired, run different operating systems. In the case of the OpenPower 710, those can be different builds of Linux, such as mixing Suse or Red Hat, or using different kernels. In the p5 510, one can mix AIX and Linux in different partitions. IBM's implementation of partitioning is very easy to set up and manage -- I could find absolutely no way of "breaking" through one partition to see anything going on in another.

These servers have a hardwired limitation of 10 LPARS in the firmware. AIX and Suse Linux, the version I tested on the OpenPower 710, can manage the partitions dynamically. (According to IBM's literature, Red Hat Linux can't dynamically manage the partitions.) The large amount of processor cache can ensure that each partition runs efficiently, without causing excessive swaps; the hardware can also be tuned very tightly, with either automatic or manual assignment of processing power to individual partitions. (I found it easier to let the server manage the processor pool.)

Fault tolerance

In any deployment, but particularly one based on server consolidation or high-performance computing, fault tolerance is key, and IBM has packed excellent features into the server, including hot-swap power, hot-swap PCI-X slots, redundant cooling, and chipkill memory protection. All that's missing is onboard RAID as a standard feature. The virtualized IO allows Fibre Channel and Ethernet to be moved between connectors, if needed, to handle a failure.

Although I couldn't test it, IBM says the Power5 processors can take portions of its own L2 and L3 caches offline if they detect or suspect problems, without a significant performance hit. The servers also contain small slide-out diagnostic panels that allow you to check for problems -- very handy, especially because the machines lack local keyboard/video connectivity.

Although no machine is perfect, these two come darned close. To be honest, I can't find any significant weaknesses in the hardware offerings. My testing spent most of the time on the OpenPower 710, merely because I'm more comfortable with Linux than with AIX. But I found both machines to be fast, solid, and reliable, and I can recommend either without hesitation.

The only worry is a broader one, regarding software support: There simply aren't as many applications and development tools for AIX and for Linux on Power5 as there are for other platforms, such as the x86 processor family. Furthermore, if you migrate to Power5, you're essentially locked into IBM's server products.

But beyond that, the learning curve is negligible, the prices are reasonable, and the platform is an excellent choice for Linux, particularly the lower-priced OpenPower 710.