The Power Systems M15 and M25 Versus Their Predecessors

June 9, 2008 Timothy Prickett Morgan

It seems like a long time since IBM announced the Power Systems convergence and the new Power6-based Power 520 i Edition 9407-M15, 9408-M25, and 9409-M50 machines, which replace the System i 520, 515, 525, and 550 boxes, which were based on the Power5+ processors. To its credit, Big Blue made a lot of progress in late 2006 with its user-capped Solution Edition Power5+ machines, which were productized as the 515 and 525 with the Power5+ chips in early 2007. The new Power Systems offer further price/performance improvements, but just how much depends on the precise configuration you look at.

As many of us have asked IBM to do for years, IBM has brought its System i and System p product lines to price parity on a common set of Power servers with the same peripherals. This is a beautiful thing. But because of the pricing IBM now has for the operating i 6.1 operating system and its integrated DB2 for i relational database and the PowerVM hypervisor, the bang for the buck on the new M15 and M25 machines is not substantially different from the older 515 and 525 servers in a lot of cases. That said, in some cases, the deal is a bit better, and in a few cases, a lot better. It all depends on the comparisons you make. Which is why I made a lot of them on your behalf.

One reason why price/performance improvements are not stellar with the 2008 version of the i boxes is that IBM has substantially reworked the instruction pipeline for the Power6 chips, a move that will, so I have been told, allow it to ramp up the clock speeds to 6 GHz and higher on the Power6+ chips, which is another 20 percent higher than the top-end 5 GHz clock speed on the Power6 chips used in the Power 595 and probably to be deployed in other Power Systems machines either later this year or early next. (My guess is early next.) But while IBM is positioning for the future and counting on new features to make Power6 systems appealing, the move from Power5+ chips running at 1.9 GHz in these entry System i boxes to the new Power6 chips, which run at 4.2 GHz, did not yield much of a performance increase for Power Systems running i5/OS V5R4 or i 6.1. Even if the Power6 chip has other features, like AltiVec vector math units and decimal math units (which no other processors on the market have and which accelerate money math), customers can only expect about 10 percent more oomph by moving from Power5+ to Power6 machines. That assessment is based on the Commercial Performance Workload (CPW) benchmark test that IBM uses to gauge the relative performance of the AS/400, iSeries, System i, and Power Systems i Edition machines.

In the past, when IBM held prices relatively stable (as it did, for instance, during the jump from proprietary 48-bit CISC to PowerPC AS 64-bit RISC chips in the summer of 1995) IBM offered customers a whole lot more processing power–in that case, RISC machines had twice the performance of the CISC machines of equivalent price that they replaced. By comparison, for the entry machines in the Power Systems lineup, the jump from System i boxes that are functionally equivalent (and can run either i5/OS V5R4 or i 6.1, just like the Power6 machinery can) is a little on the stingy side.

A lot has changed in terms of packaging and pricing in the past three generations of i-class boxes–four if you count the user-capped i5 520 Solution Editions from late 2006. And it has been for the better, particularly with the move to user-based pricing for the entry i boxes. That simple move has made the i platform more competitive with Windows, Linux, and Unix alternatives–or at least that was the case 12 to 18 months ago. Of course, X64 processor technology has moved on, Microsoft has extended is Small Business Server bundled pricing to include a new Enterprise Business Server discounted license, and Linux is still quite competitive, too. I will tackle those competitive issues in future editions of this newsletter, so don’t get the cart before the horse. For now, I am just comparing the entry i boxes from the past two years.

As you can see from the price and performance comparison table I have created for entry i boxes, there is not easy way to compare across these three generations of boxes. Two years ago, IBM was still playing games with CPW governors on the Power5+ machines, crimping performance on Value and Entry editions down to 600 or 1,200 CPWs even though a Power5+ core running at 1.9 GHz was able to handle 3,800 CPWs. Some of the entry i5 520 machines actually were allowed to run full-out, of course, but customers paid a pretty penny for these machines. Then again, these boxes were licensed to support an unlimited number of users, so companies with modest workloads and relatively large numbers of end users could justify the expense. And, of course, the i5 520 machines offered a lot better bang for the buck than their predecessors, so they seemed like a good deal at the time.

But time moves on, and with the user-priced System i 515 and 525 machines (and their Solution Edition predecessors that were a beta test of the idea in late 2006), IBM took the governors off, giving the machines full 3,800 CPW performance on a single core machine and 7,100 CPW performance on a dual-core machine, and then made its money on i5/OS licenses and user fees. IBM didn’t carve out i5/OS prices at the time, but did say an end user accessing the system would require a $250 license a pop. (That is still the price per seat for access to the system, by the way, with the new Power 520 machines, not including the base operating system.) With the Power 520s, IBM is carving out the cost of the operating system (including its database) as well as per-user fees to access that operating system as distinct from the hardware–the first time IBM has done that since 1994, when it briefly offered user-based pricing on CISC AS/400 3XX boxes. (And, it should have stayed there, in my opinion.) i5/OS V5R4 and i 6.1 costs $1,795 per processor core on a 515 or M15 box and costs $5,995 per core for an 525 box and $11,995 on an M25 box. Those cores have to be activated, of course, before the operating system can be installed, and on an M15 machine, that costs $895 after you have paid for the processor and memory card that has the electronics on it, which in the case of the M15 costs $1,536. The M25 processor card, which has two cores on it (neither activated upon sale) costs $4,577, and activation costs $2,154 per core. As you can see, a lot of the cost that used to be hardware on two-core entry hardware boxes is not expressed as software.

In the comparisons I have made across these three generations of boxes, I have calculated the cost per transaction per minute for the machine based on the CPW benchmark and my conversion of that rating to estimated TPC-C online transaction processing performance. I have also added users for the earlier machines that did not have them to calculate the cost per user. I have tried to keep machines in the same price bands or the same user bands or both whenever possible to allow for the maximum number of comparisons on the table. I have also removed Software Maintenance fees from all of the systems, even though IBM requires customers to buy it, because I think customers should have the choice of maintenance services or not (or IBM or otherwise) and because I want to isolate system costs from support costs. (I will be examining support costs for i boxes in a future edition of this newsletter. Fear not.)

In the table, two sets of rows are highlighted with a yellow tint. This is for those of you who want to cut to the chase scene and look at the most balanced and realistic comparisons. The interesting bit, as far as I am concerned, is that the Power 520 M15 with 20 users costs $17,616, which is actually more than the System i 515, which cost $16,014. Both of these machines have 4 GB of memory, four 70 GB disks and a RAID controller, a tape drive, an i5/OS or i license, a hypervisor, and 20 users. The 515 is rated at 3,800 CPWs and the M15 is rated at 4,300 CPWs, and they have a cost of 42 cents and 41 cents per transaction per minute (TPM). The price/performance did not really improve a lot, at 3 percent–you got more performance, but you had to pay for most of it. Somewhat more astonishingly, the cost per user on the 515 box with 20 users is $801 a pop for the whole setup, and rose to $881 with the M15 box. That’s a 10 percent decline or backstep in value. IBM is making this up somewhat in lower maintenance costs, I am told. But if you look at the older i5 520 machines compared to the newer user-priced boxes, the price/performance on the X15 class machines was substantial in 2007, at 60 percent on either a TPM or per-user basis. So the deal was a lot better than it has been.

Now, when you compare a 525 machine with one processor activated and an M25 with a single core turned on, each with 30 users, as I did in the yellow section, you get a radically improved bang for the buck. The 525 was overpriced in my opinion, and designed to extract extra money from customers who wanted peripheral expansion even if their computing needs were more modest. The M25 box with 30 users, which has the same configuration as the 515 and M15, costs $26,858 for a 4,300 CPW box, or 63 cents per CPW. But last year’s 525 (and this year’s if you buy one) costs $1.09 per TPM, and delivers only 3,800 CPWs. And the cost per user on the 525 comes out to $1,372–a lot more than the 515 and the M15 of equal performance and still a lot more than the $895 per user it costs for the M25 in this same configuration. This is a 42 percent better value based on TPM and 35 percent based on per-user costs.

The price/performance improvements on 40-user M15 and M25 machines and on 150-user M25 boxes are substantial, as you can see from the second yellow section at the bottom of the table. I have configured these and prior generations of i5 520, i515 and i525 machines with two activated cores (each with an i operating system), 8 GB of main memory, eight 70 GB disks and a RAID controller, and a tape drive. The price/performance improvements last year were substantial, ranging from 38 percent to 78 percent (the numbers are the same for per TPM and per user value comparisons because both the user counts and the performance are constant across the generations, just in case you are puzzled over this), depending on the configuration, and the jump to M15 and M25 machines resulted in a bang for the buck improvement of 32 percent to 39 percent on a per TPM basis and from 20 percent to 29 percent on a per user basis.

In short, the comparisons for entry i machines could have been worse, and sometimes have been. We’ll see if the prices and performance stack up against the competition, which is bringing a lot of iron to bear. But before I get into that, I will give you comparisons between midrange and high-end i boxes so you can plan your upgrades, and then comparisons to Windows, Linux, and Unix platforms so you can justify your choices to the bean counters.

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