Initial Power6 Servers Show Respectable Performance Gains

Published: May 24, 2007

by Timothy Prickett Morgan

When IBM began talking about the dual-core Power6 processors a little more than a year ago in public, it did not talk much about the performance that these chips, which include lots of integrated co-processors as well as Power execution cores. Earlier this year, when Big Blue was a little more comfortable that it could meet its chip yields and clock speeds using its 65 nanometer processes, the company's top brass felt confident enough to say that the initial Power6 chips would offer about twice the performance of the initial Power5 chips from early 2004.

Based on early the benchmark test results that IBM has provided, this is turning out to be roughly true--and true using a modified version of the existing AIX 5.3 operating system, not the future AIX 6.1 release (formerly known as AIX 5.4 until this week's launch of the Power6 chip in London) that is now expected in November and that will undoubtedly have lots of tuning to take better advantage of the Power6 chip and the related server platforms that use them.

IBM has preferred the TPC-C online transaction processing benchmark test for many years as the gauge against which it judges the performance of its AIX server line; the company's internal Relative Performance (rPerf) metric is, in fact, a variant of the TPC-C code, and it is used to show customers the relative performance gains they can expect as they add processors to an existing machine or upgrade to a larger box in the System p line. IBM may eventually shift to the TPC-E benchmark for this purpose--this test emulates a stock trading application instead of the warehouse and order entry application of TPC-C--but thus far, no one has run TPC-E and posted public results. IBM had a chance to do this with the Power6 boxes, since the TPC-E test was launched a few months ago, but has declined.

In July 2004, IBM tested a pSeries 570 server with eight dual-core Power5 processors running at 1.9 GHz, and this machine, when configured with 512 GB of main memory and running AIX 5.3 and IBM's own DB2 8.1 database, was able to process 809,144 transactions per minute (TPM) at a list price cost of $6.6 million. After a 39 percent discount, this machine was able to yield a price/performance of $4.95 per TPM. (This price includes the cost of client hardware and software to drive the simulated TPC-C users, as well as a huge amount of disk storage that is mandated by the TPC-C test. In this case, 614 TB.)

By February 2006, IBM's benchmarketeers were testing a System p5 570 server using 2.2 GHz Power5+ cores, and with AIX 5.3 and a much-improved DB2 8.2 database, this box, with the same main memory but only 61.8 TB of disk capacity, was able to push 1.025 million TPM for a list price of $7.97 million; after a 43 percent discount, IBM was able to show bang for the buck at $4.42 per TPM on the TPC-C test. That was a 27 percent performance increase and an 11 percent improvement in bang for the buck. IBM had initially hoped, way back as the Power4+ generation was waning in 2003, that it could crank Power5+ chip speeds up to 2.5 GHz and beyond to boost performance even further. But for whatever reason, this did not happen.

Jump ahead to May 2007. A System p 570 server, which has a new CPU card, a new memory subsystem, and a new I/O subsystem plugging into the same motherboards that the Power5+ servers used, has been tested with the Power6 servers and 768 GB of main memory. Like the prior two 570 boxes, this one also has 16 cores, but these Power6 cores run at 4.7 GHz. This box is running a modified AIX 5.3 operating system that knows how to speak to the Power6 chip (which is done with a patch to the kernel) and a future release of DB2 9.1 that will not be ready until this November 21. On the same TPC-C benchmark test, this Power6 box is able to process 1.62 million TPM--which is nearly exactly twice the performance of the original Power5-based p5 570 server back in 2004.

Amazingly, the System p 570 box using the Power6 chips is set up with not only 50 percent more memory, but 117 TB of disk capacity. The base 16-core System p 570 server has a list price of $2.14 million not including storage, with $1.45 million of that coming just to put all that memory in the box. The storage IBM attached to the box cost $6.44 million, and the system software cost $539,698. With client hardware and software and three years of maintenance, the total price tag for the System p 570 Power6-based system under test cost just a few bucks under $10 million. But to offset some of the cost of that storage, IBM cut the price with a 43 percent discount again, yielding a bang for the buck of $3.54 per TPM. That represents a 58 percent increase in performance of the Power6 machine over the Power5+ machine, and a 20 percent improvement in bang for the buck.

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