Power6-Based System i Performance and Bang for the Buck

Published: July 30, 2007

by Timothy Prickett Morgan

Say what you will about IBM, but in the two decades I have been following its systems and server divisions, Big Blue has done a remarkably good job providing its customers very detailed performance data to describe the amount of work that its machines can do. No other server maker provides relative performance metrics like customers buying System i, System p, and System z servers can get. As part of the rollout of the Power6-based System i 570, which was launched last week, IBM gave out preliminary benchmark test results.

As you might imagine, the relative increase in the performance of the new System i 570 server against its predecessors in the iSeries and System i product lines depends on the nature of the test. Like the Commercial Processing Workload (CPW) test that IBM has used to measure relative performance since it retired the RAMP-C transaction processing test 11 years ago. CPW is loosely based on the Transaction Processing Council's TPC-C benchmark test, but one that has been tweaked to make it easier for IBM to run. CPW is an I/O intensive workload, that means the significant boost in clock speed in the dual-core Power6 processors over Power4, Power5, and Power5+ chips as well as its larger L2 cache memories do not help performance as much as on other workloads, such as IBM's own Trade6 test and the Standard Performance Evaluation Corporation's SPECjbb2005 benchmark. These latter two tests are written in Java and they stress CPUs and memories a lot more than does CPW. And therefore, given the architecture of the new System i 570, they do better on benchmarks compared to earlier iron.

Since CPW is what most customers use to reckon performance, given that they tend to run online transaction processing on their OS/400 and i5/OS servers and that IBM has priced AS/400, iSeries, and System i servers based on first RAMP-C and then CPW, the performance boost from moving to the Power6 chip is probably most important. I will discuss the CPW results this week, and then follow up in subsequent stories with results on other tests, including IBM's Domino Mail and Calendar test and SAP's Business Intelligence data warehousing test.

Back in the second quarter of 2001, when the iSeries Model 840 was the big bad AS/400 box, the product line used 600 MHz S-Star Power processors, and the largest machine had 24 processors and a rating of 20,200 on the CPW test; the base machine cost $1.47 million with minimal 5250 processing capacity and $5.8 million with full 5250 capacity. If you could order a 16-processor version of this machine, it would have cost just under $1 million with no green-screen processing, no memory, and no disks and it would have maybe done 15,000 CPWs of work. (When you paid that money, all the processors were turned on, too.) For the basic central electronics complex, or CEC, as IBM calls it, it cost about $65 per CPW without 5250 capacity and a stunning $4 million with green screen capacity turned on.

In the second quarter of 2003, the high-end of the iSeries line got the dual-core Power4 processor running at 1.3 GHz; the low-end 8XX models were still based on S-Star chips running at 540 MHz and 750 MHz. At that time, a 16-core iSeries 890 was rated at 20,000 CPWs, and the base machine without any 5250 capacity cost $900,000, or $45 per CPW. With 5250 capacity activated across all cores using OS/400 Enterprise Edition, this box cost just under $2 million, or $99 per CPW. (These prices did not include Software Maintenance or monthly maintenance fees.) IBM cut the cost of 5250 capacity in half with these announcements. OS/400 was bundled into the price of the hardware at this time.

In the second quarter of 2004, IBM debuted the dual-core Power5 processors in the iSeries line, and the biggest machine initially in that line was the i5 570, which spanned from two to 16 cores and which resembled, in basic design, the same four-chassis system that IBM has plunked the Power6 chip into. This i5 570 machine with 16 1.65 GHz cores was rated at 44,700 CPWs. The base machine with 13 cores cost $269,000 with OS/400 Standard Edition on the 13 cores in the largest box, and $1.22 million running OS/400 Enterprise Edition. Activating the remaining three cores in this box cost $23,100. Adding OS/400 to these cores cost another $135,000, and adding 5250 Enterprise Enablement to the remaining three cores would cost $250,000. When you do the math, a 16-core i5 570 using the 1.65 GHz processors and running OS/400 Standard Edition would cost $427,100 for just the CEC and the operating system, or $9.55 per CPW. To run green-screen apps across this whole box would require a base machine that cost $1.63 million, or $36.49 per CPW.

In January 2006, IBM rolled out the Power5+ processors and put the 2.2 GHz version of these chips--the fastest the company offered at the time--into the i5 570. This boosted performance by 31 percent to 58,500 CPWs compared to the Power5 chip. With i5/OS V5R4 Standard Edition, a 16-core CEC cost $509,592, including processor activations for eight cores not included in the price of the base box, adding i5/OS to those eight cores added another $472,000 to the cost, bringing the total for a base machine that could not support green screens apps to $981,592, or $16.78 per CPW. That was a lot more per CPW for the server-style i5/OS support, which explains why IBM has been constantly messing around with pricing on the i5 570. With Enterprise Edition and its 5250 processing capability, this machine cost $1.49 million, or $25.41 per CPW. This was a pretty substantial cut in green-screen processing costs.

That brings us to the new Power6-based System i 570, which is rated at 76,900 CPWs when it is fully loaded with cores. And with 16 of the top-speed 4.7 GHz Power6 cores, the money still adds up to a big pile. The base CEC with eight cores activated costs $340,000. It costs $17,700 to activate a core, so pushing it to eight cores costs another $141,600. i5/OS is on the first four cores, but adding it to the remaining dozen cores costs another $708,000. If you want 5250 processing, it costs $50,000 per core. There is no longer a Standard or Enterprise Edition differentiation on this machine--you pay for what you use.

So to create something that would have been called a System i Standard Edition machine would cost $1.19 million, or $15.47 per CPW, while a machine modeled after Enterprise Edition with full 5250 processing would cost just under $2 million, or $25.87 per core.

In plain English, prices for the new Power6 box are essentially the same as the old Power5+ box. The difference is, you don't have to load it up with i5/OS, you can deploy i5/OS Application Server where you don't need the database (and for only $19,000 per core instead of $59,000 per core for the full i5/OS license), and you can reasonably and affordably collapse Linux and AIX loads on this machine, too.

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