Big IBM i Shops Get Beefier Memory
February 1, 2016 Timothy Prickett Morgan
While there is no question that the installed base of OS/400, i5/OS and IBM i machinery in the world–probably something on the order of 150,000 machines–is dominated by small machines with one or two processors and only a couple of cores at most activated, there are still some very, very large customers out there. These companies are driving the performance requirements for Power Systems iron, just like big AIX and Linux shops are doing.
While all of the world gets in a tizzy over in-memory processing, the single-level storage architecture of the System/38’s CPF and the AS/400’s OS/400 make this a no brainer. These machines, and their follow-ons–the iSeries, the System i, and now the Power Systems running IBM i–all do “in-memory” by default, without any fuss or muss. In fact, if you wanted to take a Power8 machine with a couple of flash drives with a few hundred gigabytes of capacity for holding an IBM i boot image and then slap on a couple of terabytes of main memory, I think you could make a hell of a fast in-memory database, and you would not have to port your applications to SAP HANA on Linux or DB2 BLU on Linux or Unix or Oracle 12c on the same. If I were IBM, I might be showing this benefit of IBM i off, if it were not for the fact that IBM wants to sell Power Systems iron supporting SAP HANA, DB2 BLU, and Oracle 12c.
The good news for IBM i shops is that as IBM tries to encourage customers to move in-memory databases to the Power Systems platforms, this is driving up main memory requirements. And so IBM is doubling up the main memory cards it makes, which is calls Centaur DIMMs, or CDIMMs for short, to a maximum capacity of 256 GB. These are the fattest memory cards on the market, and are twice as dense as the fattest 128 GB cards IBM shipped a few months after the Power8 chips launched in April 2014. (That seems like a long time ago, doesn’t it?)
The Centaur chip, which resides on the memory card, contains a chunk of the memory controller that is specifically related to translating signals coming off the Power8 memory bus on the on-chip memory controller to the format required for either DDR3 or DDR4 main memory chips. With the Power8 chips, IBM is only supporting DDR3 technology, which was on the cutting edge when the Power8 chips first came out in Power Systems. (IBM likes to hang back a chip generation when it comes to main memory, a practice that lets it boost its margins perhaps but which does not allow it to make the densest and most energy efficient systems it can.) The Centaur chip also includes an L4 cache that sits between the main memory and the CPU complex, helping to boost performance. IBM does not run the fasted memory possible, but the initial Power8 design allowed for up to eight memory sticks to hang off of a single Power8 socket, for a total of 1 TB of memory per socket. With the double-stuffed memory cards that IBM put out in announcement letter 116-004, the E-Class Power E870 and Power E880 machines now can have up to 2 TB of memory per socket.
IBM is not providing any benchmarks or specifications about how such large blocks of memory might affect system performance, but obviously more memory is a good thing in a lot of cases. And the fact that the new 256 GB cards are priced at the same level as the old 128 GB cards means companies buying E-Class Power Systems machines now can go with the fatter memory and half populate their memory slots for a given amount of memory capacity, leaving room for a memory upgrade later.
As with all of the memory in its high end Power Systems machines, the memory card using the new 256 GB CDIMMs, which goes by feature #EM8Y in the IBM catalog, comes with all of its capacity physically installed and then it has to be activated. In this case, the #EM8Y memory card has four slots, each with a 256 GB CDIMM, and it costs $64,240. Activating each gigabyte of capacity on this card costs $93.46 on top of that, and if you do the math, the price tag for a fully activated card is $159,946, which comes to $156 per GB. If you want to fill up an entire Power E870 or E880 node, with 32 memory cards, this will run you $1.28 million.
This is the main reason that I do not think IBM will require that Power8+ systems, which are expected to ship sometime later this year, support DDR4 memory. The memory that companies buy is so expensive that they will want to preserve it if possible. Memory is not cheap in any server, mind you. Over at Oracle, a plain old 32 GB DDR4 memory stick with no L4 cache that plus into the new Sparc M7-16 server that is roughly equivalent to the E-Class costs $1,224, or $38.25 per GB. Yes, the IBM memory is way more expensive, but it does more, too. My guess is the IBM Power Systems memory sells on the street for 40 percent off list, and that Oracle doesn’t discount much at all.
One other thing: You have to go all in to use the fatter 256 GB CDIMMs, so on the Power E870 that means buying 8 TB and on the Power E880, that means buying 16 TB. These are very expensive memory modules for IBM to make and it is not messing around. You can do the scale up and down of memory using the 32 GB, 64 GB, and 128 GB CDIMM memory IBM already sells, and we think that if you squeak IBM will let you do memory on demand with the 256 GB memory as well, even though this is not explicitly allowed. There is no technical reason why IBM is doing this–it is entirely driven by economics.
In addition to beefing up the memory on the Power E870 and Power E880 machines, IBM is also making the 10-core, 4.19 GHz Power8 processor that it originally sold on the Power E870 available on the Power E880. In the fall of 2014 when the E-Class Power Systems machines were launched, the Power E870 was offered with one or two server nodes linked together using NUMA links either with an eight-core Power8 running at 4.02 GHz or a ten-core Power8 running at 4.19 GHz. The Power E880 was launched with eight-core Power8 chips running at 4.35 GHz yielding a maximum footprint of 128 cores across eight sockets, and in May last year, a twelve-core chip running at 4.02 GHz was put out with a maximum footprint of 192 cores. Steve Sibley, director of worldwide product management for IBM’s Power Systems line, says that customers saw that 4.19 GHz option and wanted something to shoot the gap between the 128-core and 192-core Power E880s, and so IBM is moving in a ten-core Power8 running at the intermediate 4.19 GHz clock speed.
“We still have quite a number of IBM i clients that need all the scale we can give them,” says Sibley.
We would sure like to talk to them and find out what it is like in the rarified air of IBM i scalability here in 2016 and compare and contrast that to what it was like 10, 15, 20, and 25 years ago.
These tweaks probably represent the last changes in the Power Systems line from IBM until new Power8+ systems come onto the market. OpenPower partners are still doing their things, however, and it stands to reason we will see some machines come out during the OpenPower Summit in early April from all kinds of companies.
The fatter 256 GB memory card will be available on March 18, and the new processor option for the Power E880 is available as of January 29.