The System iWant, 2010 Edition: Midrange Boxes

Published: January 25, 2010

by Timothy Prickett Morgan

The midrange of IBM's Power Systems lineup is too complicated as it now stands, and IBM needs to once again simplify the product line while at the same time providing different chassis options to customers who have varying needs for peripheral storage such as disk, flash, and tape drives. With the launch of the Power7-based machines, due for their initial launch in February, likely with more machines rolling out as 2010 unfolds, Big Blue has a clean slate with which to work.

Last week, I talked generally about some of the things that IBM should consider doing for its high-end Power 595-class machines, which you can see here. In many ways, this is the easiest box to spec out in terms of its feeds and speeds, even if it is the most complex and expensive Power-based machine for IBM to design, build, sell, and support. The midrange might seem to present an easier set of requirements to meet, but then again, there is not one midrange customer so much as a really wide spectrum of them, all with different needs.

Right now, there are four different midrange rack and tower servers in the Power6 and Power6+ lineup: the Power 550, 560, 570, and 575. (I am not counting JS43 blade server, which is a midrange-class machine of a sort. I will deal with what I think IBM needs to do with blades.) With the Power 550s, IBM puts a single dual-core Power6 or Power6+ chip and its DDR2 main memory on a processor card, and puts as many as four processor cards (each with eight memory slots) into a 4U chassis that can be mounted in a rack or tipped on its side and deployed as a tower box. As X64 servers were building up their core counts, IBM put out a Power 560, which crammed two Power6+ chips onto a single card to boost the core count, but the clock speed on the cores had to be dropped down to keep it from melting. The net gain was a machine with about 30 percent more oomph that could support twice as many logical partitions as the Power 550 as well as 50 percent more main memory (384 GB) and twice as many logical partitions (160).

In many cases, the Power 560 obviated the need to move to a Power 570 class machine, variants of which were delivered with single-chip and double-chip processor cards using Power6 or Power6+ chips. The double-chip cards were only available with the Power6+ chips, and packed 32 cores, 160 partitions (not 320 as you might expect), and 768 GB into a single system image. That large image was not created in a single package, but rather is created by taking four 4U boxes, each with two processor cards, and lashing them together with fiber optic cables and a homegrown Power SMP chipset. The Power 570 was aimed at customers who needed more memory and peripheral expansion than was available in the Power 550, and then the Power 560 when it debuted in October 2008; the Power 570 (although it wasn't called that at the time) came out in May 2007 and the Power 520 and 550 machines came out the following February.

Finally, there is the Power 575, a water-cooled supercomputer node that comes in a 2U form factor, which is 24-inches wide like the Power 595 and crams 32 cores into that space. This machine will be replaced by the Power7 IH supercomputer node (which I told you about back in November), a 2U custom-sized node with switching and 256 cores crammed into the node. The Power 575 did not support any variant of i/OS, and the Power IH node won't, either.

Let's start with the future 570-class machine first and see what it might look like. IBM has promised customers with Power 570 and Power 595 machines using Power6 or Power6+ processors that they will get upgrade protection. This probably means the Power7 machine that replaces the current Power 570s will look similar to those current boxes. That means we can expect a 570-class box to have from one to four chassis. Now, with clock speeds expected in the range of 3 GHz to 4 GHz on the Power7 cores (and quite possibly lower on some machines), IBM has to jack up the number of threads per core and the number of cores per chip to compete against dual-core, dual-thread Power6+ chips running at between 4.2 GHz and 5 GHz. Now, if IBM keeps the basic 570-class machine architecture the same--two processor cards per chassis with one or two chips per card, spanning up to four chasses in a single system image--then IBM can double or quadruple the number of cores per box. At quadruple the cores, but running at around 20 to 30 percent lower clock speeds, you can get about three times the throughput. But that also would require about three times the main memory, unless that embedded DRAM (eDRAM) L3 cache on the Power7 cores means workloads might need less main memory to run. The question is, how is IBM going to cram all that DDR3 memory into the chassis if it is indeed adding that many cores?

The other issue with lowering the clock speed and boosting the core count on the 570-class machine is that i/OS prices per unit of performance are going to rise. This is why the Power 560 was unattractive to many i/OS shops compared to the Power 550 or the Power 570. And this is another reason why I think IBM should just sell the hardware and give the operating system away for free. (I know, funny, right?)

Suffice it to say, IBM has a lot of different ways it can skin the high end of the midrange cat with the Power7 machines.

Ditto for the 550 and 560 classes of machines. For one thing, I think IBM should consolidate these back to one product, and I would go so far as to say that it would be better still to offer 2U and 4U chassis with different peripheral and processor options and collapse the Power 520, 550, 560, and 570 machines into one box. This way, if you want to build out SMP configurations like the Power 570 does, you slap in a chipset and the interconnects and away you go. A company investing in a Power 550 should have been able to move in the Power 560 or Power 570 directions without too much hassle. The 2U chassis could offer two processor cards (with two Power7 chips with half their cores deactivated, or eight working cores, per card) and the 4U chassis could offer four processor cards (for 16 cores per chassis if IBM uses half duds here, too). The need to put lots of memory on such processor cards and not having room for two sockets might limit them to only one full-working Power7 chip per card. Either way, a 550-class 2U box would have a maximum of 16 cores (twice as many as the current 550, but running with lower clock speeds) and a 570-class, four-node machine made of 2U chasses would have 64 cores--twice the top-end Power 570 sold today. A Power7 box based on a 4U chassis might offer double this amount, depending on how the processor cards slip into the server, or 128 cores in a four-node configuration. That would be half the 595-class machine, but probably with lower clock speeds and a lot less main memory per core.

The main thing is that IBM has to be able to demonstrate that more CPWs of work will be done by the new Power7 midrange machines to justify customers shelling out the money to move up to them. And it can't price the i/OS software stack so the software goes up to get that performance. Having already slashed memory prices on Power Systems machines at the end of November last year by between 28 percent to 70 percent, I don't think customers can expect lower memory prices than what IBM is currently charging for a given class of machine in the midrange of the line.

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