That Faster Power 750 Motor Is Made for IBM i Shops
April 25, 2011 Timothy Prickett Morgan
When you pay for your operating system on a per-core basis, not a per socket basis, and that operating system includes a relational database and costs as much as Big Blue charges for the IBM i platform, there is one thing I can tell you for sure: you want the fastest processor that IBM can ship, and you don’t want to pay for extra cores you will never need, to get the best bang for the buck.
And lucky for OS/400 and i shops, IBM has added just such a processor to the Power 750 midrange machine.
As The Four Hundred discussed in last week’s issue, IBM has boosted the processor speeds in the four-socket Power 750 workhorse server while at the same time doubling up the socket count on the PS7XX series of blade servers. That socket doubling was accompanied with a reduction in clock speed on the Power7 processors, from 3 GHz down to 2.4 GHz, so this is moving in exactly the wrong direction for IBM i. Yes, there are more cores and more threads per blade now, which in theory should make a database run more efficiently even at the lower clock speed. But with per-core software and maintenance pricing like IBM uses for the IBM i platform, the software charges very quickly eat you alive if you intend to support just IBM i on the machines.
If you only have modest IBM i workloads and you plan to use most of the cores on the new two-socket PS703 and four-socket PS704 blade servers to support AIX or Linux workloads–perhaps file, print, and Web servers to Linux, and maybe even some application servers, relegating the IBM i cores to running legacy RPG applications and serving up data for legacy and Webby apps alike no matter what partitions they run on–then this is a different story. Then the new PS703 and PS704 blades might be for you.
Last fall, I ginned up some comparisons showing the relative cost per core and per unit of performance, as gauged by IBM’s Commercial Performance Workload (CPW) benchmark test, for the base processor feature cards and core activations across the Power7 lineup. You’ll find the hardware-only comparison here and one that adds in the costs of IBM i licenses and Software Maintenance (SWMA, which is actually both hardware and software maintenance, despite its name) there.
This week, I added the two new PS7XX blades and the four new processor options for the Power 750 to the mix. You can see them highlighted in a color that could be light green or beige–I am not actually sure, being a man and all–in the patent-pending monster Power7s processor feature price/performance table I have created for this story. In both the comparison last fall and the one this week, I have taken a processor feature, activated all the cores on the card if they are not already, slapped on IBM i onto each core, plus ten users per core if there are per-user fees for the IBM i license. Then I also back out the cost of SWMA from the initial license and break it out as a separate item, as it should be to correctly show the breakdown of hardware, software, and support costs for the base processor features. These costs do not include the cost of a blade chassis or motherboard and rack or tower chassis, and also do not include memory, disk, and other peripherals. This is merely a way to gauge the cost of raw processing capacity across the Power7 lineup, regardless of the box you put it in or how you glue those processors together into larger system images.
If you assume that all of the cores are running IBM i, the new PS703 single-wide, two-socket blade gives less bang for the buck than a double-wide, single-socket PS702 blade server. The former yields 76,300 aggregate CPWs across its 16 cores running at 3 GHz and costs $3.81 per CPW, while the latter yields 64,0000 across 16 of the slower 2.4 GHz cores at a cost of $4.52 per CPW. The benefit, however, is that the new two-socket blade allows twice the CPU density in a BladeCenter chassis, and this is important for many supercomputing customers that IBM sells its Power-based servers too. The two-blade, four-socket PS704, with 32 cores running at 2.4 GHz, offers 110,000 CPWs of aggregate performance across its two blades, which is about 44 percent more raw oomph than the PS702 can muster. But this double-wide PS704 blade fully loaded with IBM i licenses (with 10 users per core) and a year of maintenance–without any Power Systems Express configuration discounts, of course–will run you $458,942, which works out to $5.34 per CPW. The entry four-core PS700 blade has cheaper IBM i and SWMA fees and only costs $1.26 per CPW.
Here’s how the different blades look in terms of the breakdown between hardware, software, and support costs for all the cores loaded up with IBM i:
The software bill just utterly dominates the overall cost–just like hardware used to two decades ago. They have basically switched positions.
On the Power 750 front, I think a lot of IBM i shops are going to take a shining to that four-core feature EPA3 option for the machine, which runs at 3.72 GHz. With all four cores activated, you’re talking $24,426 for a single processor card and 27,300 aggregate CPWs. Load it up with IBM i and a year of support, and the price works out to $260,426, or $9.54 per CPW. That’s almost a buck cheaper per CPW than the six-core, 3.3 GHz feature 8335 processor card that launched with the Power 750s a little more than a year ago. In general, as you can see from the chart below, the new Power 750 processor features show better bang for the buck compared to the older features:
Obviously, just looking at the hardware alone, the new features in many cases offer a lot better value for the dollar. But because software and support costs are the same between old and new features, and these factors are much more expensive than hardware, the improvement in bang for the buck is mostly wiped out.
That said, it still beats a swift kick in the teeth. Or somewhere worse.