IBM Tweaks Memory And I/O For Entry Power9 Iron

July 16, 2018 Timothy Prickett Morgan

The summer is usually pretty quiet in IBM i Land, and this one is no exception. But things do still happen, and it is our job – and we like our job – to keep you informed of things when they do.

On July 10, while IT Jungle was away on summer break, Big Blue did some tweaks and changes for various elements of the entry Power9 machines that started rolling out this year. These are all little things, but as usual, the little things can add up.

In announcement letter 118-058, IBM has interestingly announced a new 8 GB memory feature for the “ZZ” family of Power9 servers that made their debut back in February and that we subsequently drilled down deeply into the feeds and speeds here. The new 8 GB memory card is feature #EM60 on the Power S914, Power S922, and Power S924 plain vanilla servers and the Power L922 Linux-only server, and feature #EM6G on the Power H922 and Power H924 machines for SAP HANA. You might be thinking that it is pretty silly to have an 8 GB memory card in this day and age, but it is not for a number of reasons. First, memory is more expensive than anyone thought it would be right now due to fab shortages and increasing demand from personal and client devices, which are more profitable than server memory. (Strange as it may sound.) Moreover, with eight memory slots per socket, and a relatively modest footprint, having the base memory stick weigh in at 16 GB is overkill for a lot of workloads, and can add up to many thousands of dollars of incremental investment. And finally, with a 64 GB cap on the Power S914 for IBM i workloads running on the four-core variant of the Power9 processor, that would mean only putting four memory sticks in the box. So what, you say? Well, with only half the memory sticks in the box, that also cuts the memory bandwidth in half, and in many cases, workloads have bandwidth bottlenecks as much as they have capacity needs. By switching to an 8 GB stick, all eight of the slots on a single-socket machine can be populated, giving full memory bandwidth, and still come in at the peak 64 GB capacity. So the memory is skinny, but fast. (I know what this feels like.)

As is often the case, IBM did not explain itself here, so I am just guessing. But I think this is a pretty good rationale for an 8 GB memory stick on Power9 entry servers. What IBM did not do is provide any pricing on this 8 GB memory stick, or indeed any of the other peripherals it announced on July 10. We did an analysis of memory for Power8 and Power9 entry servers back in March, and then followed this up with an analysis of IBM’s fairly modest memory price increases in June. The price increases were highest for fatter memory sticks based on DDR4 memory chips, and on the 16 GB memory, the price was $630, up 2 percent from the $619 that IBM was charging on announcement day back in February. This was a lot lower, mind you, than the $1,250 that IBM was asking for 16 GB memory using DDR3 chips for Power8 machines, and still considerably higher than the $1,110 for the DDR4 sticks at 16 GB that eventually came out for Power8 iron. Clearly, IBM was overcharging like crazy for Power8 memory if the price hike was so modest back in June. In any event, if you do the math backwards and shave a little bit extra off for an 8 GB stick, they should cost around $300 a pop, so 64 GB costs around $2,400 for eight sticks – a little less than four sticks at 16 GB a pop – but the machine has full memory bandwidth, not half. It also means all of the memory slots are full, so if you need to add memory, you will have to throw the old stuff out. So configure carefully.

In addition, IBM has made the feature #EJ32 and #EJ33 cryptographic coprocessor and accelerator cards available on the Power S914, Power S924, and Power H924 servers. This accelerator is based on a PCI-Express Cryptographic Coprocessor 4767 platform, and provides AES-256 encryption/decryption and hardware-accelerated Elliptic Curve Cryptography (ECC) key generation that meets FIPS 140-2 level 4, among other things. It only runs in bare metal mode and cannot be virtualized for PowerVM logical partitions, according to the announcement letter. (This strikes me as odd.)

IBM is also floating out a new two-port 8 Gb/sec Fibre Channel adapter card, features #EL5Y and #EL5Z, that have the same functionality as the generic feature #EN0F and #EN0G adapters, but with a lower price. (Yes, this annoys the crap out of me.)

For customers who want to move on up to the mid-2010s in terms of networking, IBM is now offering a two-port 40 Gb/sec Ethernet adapter that supports the RoCE remote direct memory access protocol, which is feature #EC3A on the Power S922, Power L922, and Power H922 and feature #EC3B on these three machines plus the Power S914, Power Ps24, and Power H924 machines. (I have no idea why they are different features. It seems odd.)

IBM is also now allowing for feature #5887 and #EL1S EXP24S expansion drawers to be migrated from older iron to Power9 iron. To be precise, feature #EL1S is available on the Power L922 and feature #5887 is available on the Power S914, Power S922, Power S924, Power H922, and Power H924 machines. There are some limitations, as outlined here:

One EXP24S drawer in mode 1 can be attached to the two SAS ports on the rear of the server using three-meter SAS YO cables such as feature ECBT or ECBU. Either SSDs or HDDs can be placed in this drawer, but SSDs and HDDs cannot be mixed in this drawer.
The EXP24S drawer (#5887/#EL1S) can be attached to SAS ports of PCIe SAS adapters using SAS YO or X cables. Up to 28 EXP24S drawers can be attached. The specific SAS cables used will depend on the specific adapter selected and drawer mode selected. Either SSDs or HDDs can be placed in the drawer, depending on the capabilities of the adapter running the bays. Note that longer distance SAS cables are thicker and can fill the Cable Management Arm more quickly.
With AIX, Linux, and VIOS, you can migrate the EXP24S with four sets of six bays, two sets of 12 bays, or one set of 24 bays (mode 4, 2, or 1). With IBM i, you can migrate the EXP24S as one set of 24 bays (mode 1). Mode setting is done by IBM Manufacturing, and there is no option provided to change the mode after it is shipped from IBM.
The EXP24S SAS ports are attached to a SAS PCIe adapter or pair of adapters using SAS YO or X cables.

And finally, the ancient PCI-Express 1.0 dual-port 3 Gb/sec SAS Tape/DVD adapter that has been used on many generations of Power Systems is now available on the Power L922 server as feature #EJ1N (low-profile) and #EJ1P (full height) adapter cards.

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