IBM’s Power7 Blades Pack a CPW Punch

April 19, 2010 Timothy Prickett Morgan

The Power7-based Power Systems lineup got a little rounder and fuller last week as IBM kicked out two new blade servers based on the eight-core Power7 chips that made their debut in midrange rack-based servers back in February. The new Power Systems 701 and 702 blades pack a serious performance wallop, as they must do to compete with very aggressive X64 alternatives from Intel and Advanced Micro Devices.

The new PS701 and PS702 blades also offer a lot better bang for the buck compared to the prior Power6+ JS23 and JS43 blades they replace, at least based on the Commercial Performance Workload (CPW) online transaction processing benchmark test results IBM has published for the new Power7 blades. Combined with more aggressive pricing on the hardware, IBM and its Power Systems resellers will be far better able to make the case for blades at OS/400 and i shops.

The aggressive pricing and performance may also be giving us a preview into the future entry Power7 machines coming in rack and tower forms, presumably to be called the Power 720 and maybe with a Power 710 and Power 705 smaller variants (perhaps with Smart Cube SMB appliance bundles). If the past is prologue, then the future entry Power 710s and 720s should be priced very much like the PS701 and PS702 blade servers, and offer about the same oomph, too. Since April 2008, when IBM converged the System i and System p product lines, one of its goals has been to keep price parity between i and AIX hardware and systems software, but also to get the price of blade servers down to the same level as rack servers, enticing customers to move to blades and their more sophisticated management and simpler cabling. (Blades also give vendors a lot more account control, but it is hard to see how OS/400 and i shops could be more under IBM’s thumb. It’s not like there is a real alternative this side of porting applications or buying new ones.)

The move from dual-core Power6+ to eight-core Power7 processors means IBM can put a lot more cores into a lot less space, and with the PS701 blade server, that is precisely what Big Blue has done. The PS701 blade server has only one processor socket, but delivers eight cores in that socket, compared to the two sockets that were required in its predecessor, the JS23, to deliver only four cores. (This is why you try to shrink your processors as quickly as Moore’s Law allows.) By taking out one socket and rejiggering the layout of the blade, IBM not only could double up the core count on the blade, but also double up the number of memory slots, expanding from eight slots in the JS23 to 16 slots in the PS701.

Even though the JS23 used 4.2 GHz Power6+ cores, the PS701’s 3 GHz Power7 cores deliver nearly the same performance per core, thanks in large part to that giant 32 MB eDRAM L3 cache memory that IBM put at the heart of the Power7 chip. The net-net is that a PS701 smokes a JS23 blade in terms of raw aggregate performance. But each core has about 15 percent more oomph than the 4.2 GHz Power6+ cores, which could mean customers have to shell out extra money for i 7.1 licenses for the cores on the blade to get the performance they need.

Like prior Power Systems blade servers, IBM is basically offering customers one option for processors on the PS701 blade: you get an eight-core Power7 chip running at 3 GHz with 4 MB of L2 cache per core and that 32 MB L3 cache. That’s your option, like Henry Ford and his original black for cars. IBM is supporting 4 GB and 8 GB DDR3 memory sticks on the PS701, and the server has a single hot-swap, 2.5-inch disk slot that can have a 300 GB or 600 GB SAS disk. (But not yet a flash-based solid state disk, go figure.) The PS701 has a SAS disk controller, a dual-port Gigabit Ethernet controller, and two PCI-Express mezzanine slots for adding Fibre Channel, Ethernet, and InfiniBand adapters to the blade. The PS701 also has a service processor on it for managing the blade.

Starting with the LS series of Opteron blades a few years back, IBM started to design its Opteron blades to make use of an on-board HyperTransport link between two adjacent blades to turn a two-socket X64 blade into a four-socket blade with twice as much main memory in a single system. IBM adopted this approach with the two-socket JS23 and four socket JS43 blades from last April, whereby a JS43 is really just two JS23s snapped together at an SMP port. As The Four Hundred explained two weeks ago, IBM has employed this snap-together approach with BladeCenter HX5 blades using Intel’s eight-core “Nehalem-EX” Xeon 7500 processors, calling it FlexNode and allowing two blades to be linked together in an SMP configuration. IBM also has a memory extender called Max5 that allows each Xeon 7500 blade, which has two sockets (compared to one on the PS701) as well as 16 DDR3 memory slots (the same as the PS701), to add an extra 24 memory slots for the two-socket blade, pushing memory up to 320 GB for a two-socket blade. This keeps the core-to-memory ratio about the same as you get with a PS701.

Anyway, if you want more SMP scalability out of your Power7 blades, you buy feature 8358, which is essentially a PS701 blade that has its service processor removed and an SMP link feature added, and voila, you create a two-socket PS702 double-wide blade server that has 32 memory slots, topping out at 256 GB of total main memory using 8 GB DIMMs.

In terms of hardware pricing, you won’t hear a lot of complaints from i shops that are just reckoning the prices on the new Power7 blades against the prior Power6+ blades. The base PS701 comes with 16 GB of memory and no disk and it costs $5,503; it costs another $800 to activate all the cores on the blade, which you have to do unless you buy the BladeCenter 700 Express configuration, which has one PS701 blade with only four cores activated. Memory sticks are sold in pairs, and it costs $799 at list price to add two 4 GB sticks and $1,899 to add two 8 GB sticks. The 300 GB SAS disk costs $689, and the 600 GB disk costs $899; both 2.5-inch units spin at 10K RPM. If you add a SAS pass-through module to link to a SAS switch and SAS disks in the blade chassis, that costs $249.

If you configure up an eight-core PS701 blade with 64 GB of memory (half of the max and 8 GB per core, which seems like plenty for a lot of workloads), toss in the SAS pass-through and a 300 GB disk, the list price for the hardware is $12,939. This machine is rated at 42,100 CPWs of OS/400 and i OLTP relative performance, so you are talking on the order of 31 cents per CPW. By comparison, a JS23 blade with four 4.2 GHz Power6+ cores activated, 32 GB of main memory (that same 8 GB per core), and a 73.4 GB SAS disk cost $15,011; this machine was rated at 14,400 CPWs, which means the hardware alone costs $1.04 per CPW. That’s a factor of 2.9 improvement in performance–and yes, i 7.1 really knows how to make use of the four threads per core–and a factor of 3.4 improvement in bang for the buck.

The last time I saw numbers like that, it was the jump from CISC to RISC AS/400s back in 1995. And to be honest, the numbers 15 years ago were not this impressive. More like a factor of two.

Of course, the i software stack costs the same per core on Power6 or Power7 iron, so on configured systems, the difference will not be as dramatic because i 7.1 and Software Maintenance will overwhelm the hardware cost.

The same kind of improvement in performance and bang for the buck holds for this year’s PS702 blade hardware compared to last year’s JS43 blades. It costs $5,504 to buy the feature 8358 SMP expansion blade, and when you snap a PS701 blade into it to create a PS702 blade, and then configure it with 128 GB of memory (that’s half the max and 8 GB for each of the 16 cores that get activated on the two blades), plunk on a disk and the SAS pass-through module, you’re talking $26,839. This double-wide blade is rated at 76,300 CPWs, so the hardware alone costs a little more than 35 cents per CPW. But a four-socket, double-wide JS43 blade with eight cores activated, 64 GB of memory, a disk, and the SAS pass-through would run you $29,463 to get 24,050 CPWs of performance. That works out to $1.23 per CPW, which is 3.5 times more expensive per CPW than the PS702. The PS702 blade, fully configured, delivers 3.2 times the CPW oomph as the JS43 blade.

It is hard to overstate how much more computing power this is. The question is–and one that I will be working to answer in the coming weeks–once you layer on i 7.1, is the resulting system competitive with AIX, Windows, and Linux alternatives using the same Power Systems or X64 hardware?

It will be interesting to find out.

The PS701 and PS702 blades will be available in June 4. They can slot into the BladeCenter-H standard chassis, the BladeCenter-S chassis for office environments, and the BladeCenter-T chassis for telecommunication companies and service providers that need ruggedized, DC-powered computers. IBM’s i 7.1 and AIX 5.3 and 6.1, Red Hat‘s Enterprise Linux 5.5, and Novell‘s SUSE Linux Enterprise Server 10 SP3 are supported on the blades. SLES 11 will be supported later this quarter when SP1 for that OS comes out.

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