The OpenPOWER Saga Continues: Can You Get POWER Inside 1U?

Positioning the Tyan GT75

Tyan positions the GT75-BP012 as an HPC and virtualization server. But that is clearly a mistake. Since the POWER architecture has been almost completely absent in the HPC world for years now, the HPC software ecosystem is dominated by x86. The POWER HPC software ecosystem is very small in comparison. That is a fact, not an opinion, as even IBM talked about "a re-entry in the HPC market" at the end of 2015.

But people do not switch to another server ecosystem easily: there has to be a compelling reason, a Unique Selling Proposition (USP). Only the recently launched S822LC can claim such an USP; it has a much faster link (NVLink) to the best NVIDIA GPUs, and as a result can offer much higher performance in some specifically-tailored HPC applications.

The GT75-BP012 has no GPU capable PCIe slot, let alone an NVLink connection. In the cramped 1U space, the CPU is limited to 3.025 GHz, which is a bad trade-off for HPC users. The GT75-BP012 is definitely not an HPC server.

Neither is it a virtualization server, as the virtualization market lives and dies by performance-per-watt.

The only target that is left is the “In-memory computing” market, which ranges from in-memory key value stores ("Redis") to DB2 BLU. In those cases, the limited processing power is – most of the time – less important than the amount of memory that can be installed at a reasonable price. Originally, the server was limited to 512 GB (32 slots, 16 GB per slot) but it should now support up to 1 TB. We say "should" as we were not able to check this.

Still, we do not feel a 1U server is a good match for POWER8. Place that POWER8 CPU on the same Tyan "Habanero" motherboard inside the 2U IBM S812LC (and Tyan's own 2U TN71 servers) and you'll get a much more attractive server. The CPU performs 40% better, the power under load is 20% lower, and you get much more PCIe slots. To reduce it to a car analogy, a turbocharged V8 cannot breathe through a straw.

Tyan's Business Model: Direct Sales Only

As one of the founding fathers of the OpenPOWER foundation, Tyan is in a unique position. It can be the "Open and easily accessible" vendor for buyers who don't care about the different services IBM offers, but just want a fast POWER server for an affordable price. However, the truth is that it is a lot easier to buy a server from IBM than from Tyan.

While the S812LC can be found on IBM's web shop, Tyan follows the more traditional Direct Sales model. So you are meant to buy the POWER8 servers in large volumes, and pricing varies by contract. As a result of this sales model, Tyan does not readily disclose the price of this server.

Consequently, in our discussions with Tyan they were vague about pricing due to the above, which makes it very difficult for us to make any meaningful comparison to other POWER8 offerings or any Xeon-based servers. While it's of course Tyan's choice how they want to do business, we consider this a missed opportunity for the company, as all of the other OpenPOWER vendors are also targeting the customers who want to buy servers in large volumes. As a result, if you want low volumes, IBM is your only choice as far as we know.

Eye Towards the Future: POWER9

Wrapping things up, the announcement of the POWER9 SMT-4 Scale Out processor is the reason why we remain optimistic about the chances of the OpenPOWER ecosystem. A full analysis of POWER9 is beyond the scope of this article, but there is a lot we like about what has been disclosed thus far for the "Linux optimized" POWER9 SO SMT-4:

1. It is not an improved POWER8, there are many large improvements
2. A better balance between single-threaded performance and throughput: SMT-4 will be combined with a more powerful core
3. NVLink 2.0, which offers 7x more bandwidth to the GPU than PCIe 3.0
4. No more power-hogging, latency-increasing memory buffers

The POWER9 SO SMT-4 will have up to 8 DDR-4 channels, and up to 2 DIMMs per socket. This means that raw memory bandwidth and memory capacity are halved relative to POWER8, but it is a very good trade-off. The use of direct attached memory (same as the Xeon E5) lowers the latency of DRAM accesses, makes the motherboard design a lot less expensive, and lowers power consumption with 60-80W.

Add 50 to 100% higher performance per socket, and you get formidable competitor for the new Xeon E5 v4 "Skylake EP". Tyan is in a good position to make this powerhouse accessible for the rest of us, so hopefully we will see a more ambitious approach than today.