Power 750: Big Bang for Fewer Bucks Compared to Predecessors
August 16, 2010 Timothy Prickett Morgan
The Power 750 might have come to market first among the Power7-based machines, but it has taken me a bit longer than usual to cook up some comparative price/performance analysis for this midrange box, which was announced in February. I have done the work for comparisons between old and new Power blades and their alternatives in the Unix and Windows market (the two platforms that really matter for i shops), and now I will begin working my way up the product line and back down again when the entry Power7 machines (710, 720, 730, and 740) and the high-end Power7 box (795) are announced on August 17.
For this week, I want to take a look at how the various 550-class machines have delivered better bang for the buck–or not, as the case may be–since the Power5+ machine debuted in October 2005. Depending on how you want to look at it, the 550-class boxes are a rich man’s entry machine or a poor man’s midrange machine, sliding in between the entry 520 and the relatively high-end 570. The 550 was created to give IBM something to push against two-socket X64 servers with quad core processors during the Power5+ generation. You will remember that IBM got nervous enough about X64 alternatives competing against its AIX Unix that it eventually made a Power 550Q, with geared down clock speeds on Power5+ chips and doubled up chips in each socket. With the Power 560, IBM just put twice as many dual-core Power6+ chips into a 4U chassis, cramming 16 cores in the box running at 3.6 GHz.
By moving to an eight-core server architecture, the Power 750 has the kind of scalability in a 4U chassis that you would have needed in a four-chassis Power 570 to chew through your workloads. As such, the Power 750 is going to be less appealing to a lot of Power 550 shops. Particularly considering that thus far, Big Blue has not made any statements of direction about offering an upgrade path from Power 550s using Power6 or Power6+ processors to Power7-based Power 750s. Customers using older Power5+ versions of the Power 550 can upgrade to Power6 and Power6+ machines, so long as they are available from IBM and the secondhand market.
Without an upgrade path, many shops will be waiting to see what IBM has in mind for those Power 720 and Power 740 machines I told you about a few weeks ago. IBM has made a statement of direction that there will be upgrade paths from the Power 520 into its future entry machines based on the Power7 processors, but has not said much else. I hear that the Power 520 machines with two or four cores will get an upgrade path to a Power 720, but the single-core Power 520s will not. It would be interesting to see an upgrade path from the Power 550 to the Power 740, whatever that is, but I have my doubts. So if customers are going to have to kick out a machine anyway, they might as well drop down to a Power 720 and move from the P20 to the P10 software tier while they are at it. Provided, of course, their software vendors are willing to allow them to downgrade their licenses.
Providing a proper 550-to-750 upgrade path would make ISVs so much happier, since they could preserve their revenue streams.
As far as I can tell from the several Power 750 configurations I have ginned up for this story, the Power 750s have so much oomph compared to the Power 550 it is downright silly. The smallest Power 550 (with two 3.5 GHz Power6 cores activated) is rated at 7,700 on the Commercial Performance Workload (CPW) relative benchmark used for OS/400 and i machinery; topping out at eight of these cores boosts performance to 27,600 CPWs. There are 4.2 GHz Power6 cores for this machine, giving from 9,200 to 32,650 CPWs, and 5 GHz Power6+ cores, yielding from 10,600 to 37,950 CPWs.
The Power 750 is a four-socket machine, like the Power 550 was, but there are six or eight cores active on a variety of Power6 processors, and the CPW ranges are a lot wider and start at a much higher number. There is a six-core Power7 chip running at 3.3 GHz that delivers from 37,200 CPWs with all six cores turned on to 135,300 with 24 cores activated. The slower 3 GHz Power7 processors have eight cores and are cheaper per core, but those i 7.1 licenses, at $40,000 per core, are going to eat you alive. You have to do the math with your software licenses to reckon if it is smarter to pay the extra fees for the faster cores and eliminate a core’s worth of i 7.1 licenses. There is an eight-core variant of the 3.3 GHz chip whose processor card and per-core activations are quite pricey, and there is a 3.55 GHz chip that is only available in a 32-core Power 750 machine.
The Power 750 processor pricing is all over the map. Feature 8334 is the processor card with an eight-core Power7 spinning at 3 GHz; it costs $5,940 for the card and then another $3,100 per core to activate the processor. The six-core Power7 feature 8335 card, which runs at 3.3 GHz costs $7,000, plus $4,850 per core to activate. If you want the eight-core 3.3 GHz Power7, that’s feature 8332 and it costs $12,400 for the card plus $6,000 per core. And if you want the top-end eight-core Power7 running at 3.55 GHz, that’s $17,700 per card for feature 8336 plus $9,000 per core. Here’s a table to help you think about the four different processor options:
The fully loaded, top-end Power 750 with those 32 Power7 cores running at 3.55 GHz and rated at 181,000 CPWs is way overkill for the typical Power 550 shop. As the table shows, you have to ask yourself once and then twice if you think you need those 3.3 GHz cores, too, especially those eight-core Power7 processors cards, which cost $7,550 per core (including the base feature card and processor core activation fees). That extra 10 percent in clock speed ends up nearly doubling the per-core hardware cost. You can make a better case for the six-core Power7 cards, which offer that 10 percent performance boost, but still cost 57 percent more per core. Some companies are going to be compelled to move to the 3.3 GHz cores to get incremental per-core performance enhancements, but if you need to do that, for heaven’s sake, stay away from feature 8332 and 8336 processor cards.
Unless you are loading them all up with i 7.1 and the 5250 Enablement features. On the Power 750 machines, i 7.1 costs $40,000 per core, and after a recent price break from $50,000 to $15,000 per core for 5250 capacity, shelling out more for faster cores with more performance to curtail software fees doesn’t really work on machines with relatively few cores, as most Power 550 shops have. If i 7.1 had a much lower price, you’d have to be a lot more careful about which cores you are picking. But on these machines, the hardware accounts for a mere fraction of the system cost. It is the software that accounts for most of the money in the system.
In the 550-class monster comparison table I put together for this story, I tried to gin up comparisons of Power 550 (Power6+) and Power 750 (Power7) machines that delivered a successive but incremental performance improvement compared to the System i M50 from early 2008, which were based on the Power6 processors and predate the Power Systems convergence. In the comparisons, I convert CPWs to transactions per minute, estimating the performance of the boxes on the TPC-C online transaction processing benchmark if they were loaded up heavily, and then put a base amount of main memory, disk, and a tape drive on the box.
The first comparison in each generation is for a base, lower-cost machine without 5250 capacity. In the first set of comparisons, I have two cores, with OS/400 or i activated on both cores, and I eventually activate one core for 5250 processing. In the second set, the machines are configured with four cores and all four cores have 5250 enabled on them as well as OS/400 or i. In addition to calculating per transaction costs for the configured systems, I also put the typical number of users on the boxes from the user-priced M25 and M50 categories used by IBM years ago–10, 30, 40, 80, 150, and 300. The configurations are designed to show the cost per user as users are added and load up the systems.
The first thing that is obvious from this table is that the System i5 550 machines based on Power5+ processors were ridiculously expensive and that the user-priced System i 525 servers based on exactly the same iron (but only with two cores) were limited in their scalability, but just wickedly less expensive than anything in the 550-class. We’re talking 76 cents per CPW on a 40-user box rated at 7,100 CPWs. The base Power 750 box I created using the 3 GHz Power7 chips (and only activating two cores for running i 7.1) is rated at around 11,150 CPWs, or 57 percent more oomph, but at a cost of $1.01 per CPW. When you compare these machines on a per-user basis, the System i 525 with 40 users cost $1,345 per user, but the base Power 750 I set up cost $2,796 per user.
In general, on 550-class machines, the cost per CPW has been trending down at around 30 to 40 percent, depending on the configuration, but the cost per user has been going down by 10 to 40 percent. In many cases, on entry configurations, the cost per CPW and per user goes up with each generation, not down. All of the data is in the table, but below is a picture that wraps it up. Remember, this chart presumes slightly increasing CPWs for the two socket boxes over time, but nothing crazy.
The good news for customers with 550-class machines who are needing to upgrade to Power 750 boxes is that the cost per user is significantly lower on the Power 750s with i 7.1 and 5250 enabled on the cores because of that 5250 Enablement price cut. On a Power 550 or 750 box, 5250 capacity costs $60,000 across all the cores in the box instead of $150,000. (It costs $15,000 on a single core, instead of $50,000 previously.) This really cuts the cost per user down to under $1,000 per user on machines with 150 or 300 users. On a somewhat loaded Power 750 with eight cores, the cost per user on a machine with 600 users drops down to under $650 to $750 per user. On a heavily loaded Power 750 using the cheap 3 GHz Power7 chips with the full 32 cores on and the full 512 GB of memory installed, you are talking about a minor $25 per user difference between having 5250 turned on and not, with it costing $655 per user with 5250 enabled.
If anything, I would expect a fair number of shops with big Power 570 and entry Power 595 boxes to take a serious look at the Power 750 if their I/O requirements are fairly low.
That’s the first thing. But as I reported last week, IBM is allowing customers to slide over their i 6.1.1 and i 7.1 licenses from Power 550 machines to Power 750 machines at $5,000 per core excepting for the initial i license; 5250 enablement features are also being allowed to slide over for $5,000 per core. While this is not an upgrade, this is a significant savings for customers.
Let’s take one example, the Power 750 I set up with 32 GB of main memory, eight disks, and four of the 3.3 GHz cores supporting 300 users. That machine, purchased new, costs $281,913 with i 7.1 and 5250 on all four cores, or $940 per user. Sliding over three OS/400 V5R4M5 or i 6.1 licenses to i 7.1 and sliding over four 5250 enablement licenses drops the price to $136,913 for a new machine, or $456 per user. It nearly cuts the cost in half. This savings, more than anything else, is why Power 550 customers might do a push-pull upgrade to a Power 750 even if Big Blue doesn’t get around to offering a formal hardware upgrade.