The OpenPOWER Saga Continues: Can You Get POWER Inside 1U?
by Johan De Gelas on February 24, 2017 8:00 AM ESTEnergy Consumption
We know that the POWER8 was not designed to be a performance-per-watt champion. Throughput, single threaded performance, and RAS were the main priorities. However, Tyan does position the GT75 as a virtualization server. In that market, performance-per-watt is important.
We tested the energy consumption of our servers for a one-minute period in several situations. The first one is the point where the tested server performs best in MySQL: the highest throughput just before the response time goes up significantly. Then we look at the point where throughput is the highest (no matter what response time). This is the situation where the CPU is fully loaded.
The final column is calculated by dividing the best throughput by the power usage. We define the "best throughput" as throughput where the balance between throughput and the 95th percentile response time is the best. In other words, beyond that point, throughput increases only slightly (less than 10%), but the response time increases much faster.
| SKU | Server Height | TDP (on paper) spec |
Idle Server W |
MySQL Best Throughput at Lowest Resp. Time (*) (W) |
MySQL Max Throughput (W) |
Transaction /s (**) |
Tr/watt ( = ** / * ) |
| IBM POWER8 8c@2.3 Tyan | 1U | 170 W | 171 | 323 | 330 | 10300 | 32 |
| IBM POWER8 10c@2.9 S812LC | 2U | 190 W | 221 | 259 | 260 | 14482 | 55 |
| Xeon E5-2699 v4 | 2U | 145 W | 67 | 213 | 235 | 18997 | 89 |
| Xeon E5-2640 v4 | 2U | 90 W | 76 | 135 | 145 | 9541 | 71 |
| Xeon E5-2690 v3 | 2U | 135 W | 84 | 249 | 254 | 11741 | 47 |
At idle, both of the POWER8-based servers reduce their clockspeed to 2.06 GHz and power-gate the cores they do not need. However, the Tyan GT75 PSU is probably more efficient in this case, and the GT75 is a less complex server as well. As a result, the idle power is significantly lower than the S812LC. Still, it is nowhere near the Intel Xeons.
Once we test the server under load, the Tyan GT75 demands a lot more power than the S812LC. That might seem contradictory at first sight, as the latter is equipped with more power hungry CPU. The main culprits are the small, extremely high RPM 1U fans inside the Tyan, which have to work hard to keep a 170W CPU cool in such a cramped environment.
Notice how the IPMI software reports 8800 RPM, but in reality the fan is running at a mindboggling 15600 RPM. A total of twelve such fans results in the cooling system as a whole consuming a lot of power.
This kind of "performance first" CPU policy really needs larger fans and more room. Case in point: in a roomier 2U chassis the load power consumption of a POWER8 setup comes very close to the contemporary 22 nm Xeon E5 v3. It will be interesting to see how this works out in the 1.25U high Rackspace BarrelEye.
Intel's "Broadwell-EP" (Xeon E5 v4) wins here by an vast margin. And there is little doubt that the next generation Skylake Xeons will probably do (slightly?) better.
However, don't count IBM and OpenPOWER out yet. First of all, MySQL is better optimized for x86-64 than for POWER8. Since MySQL is the second most popular database engine (and will probably overtake Oracle soon), we feel our choice is justified. However, it is worth mentioning that PostgreSQL (number 4) and MongoDB (5) have been fully optimized for OpenPOWER and show gains of up to 30%. Lastly, IBM's POWER9 should also do quite a bit better as a result of an improved microarchitecture and being baked with a state-of-the art 14 nm SOI process. The 14 nm POWER9 versus the "tweaked 14 nm" Intel Xeon E5 version 5 should prove a very interesting comparison.
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Amandtec - Friday, February 24, 2017 - link
Only an amateur here but I did read some of your previous articles on this. I thought the big advantage of POWER was it was encouraging 3rd parties to bring ASIC's into their server space, while Intel wan't to own the whole hardware setup? Surely ASIC's is where the whole performance per watt game ends - see Bitcoin mining.ddriver - Friday, February 24, 2017 - link
There is nothing preventing you from building your own accelerators and hooking them to a free PCIE slot.JohanAnandtech - Friday, February 24, 2017 - link
True. But you have only one PCIe 8x and AFAIK it is not an OpenCAPI one, nor an NVME capable.JohanAnandtech - Friday, February 24, 2017 - link
I meant NVLink, not NVME :-)SarahKerrigan - Friday, February 24, 2017 - link
The GT75 is a weird system and I've never been clear on why it exists. The Supermicro 1U (S821LC) at least gets you two CPU's for cheap in 1U... I'm not overly surprised by poor performance here. This is a 130W CPU, not a 170 as Anandtech says, running at low clocks. 170 is only the turbo power. I'm also guessing it's loud as hell with those fans.That being said - Anandtech also has a history of interestingly Intel-centric interpretations of results. Remember when Intel's uarch was "a lot more sophisticated" than P8 according to Anandtech based purely on ST 7zip results, and then when ThunderX did well on 7zip, Anandtech said 7z was a meaningless benchmark irrelevant to server workloads? I've also noticed that since gcc's Power output improved (~4000 MIPS single-thread compression with gcc 6.2 on 3.3GHz P8), 7zip has conveniently vanished from Anandtech's Power reviews. The idea of drawing conclusions about microarchitectures based on a balance of a range of tests seems alien to them. Looked at through that lens, Power8 (well, in systems not named GT75 :P) looks decent at some things, less decent at others, but overall pretty good. Database perf/W, per Anandtech's testing, is better than Haswell. This isn't a bad place for P8 to be, considering it's been shipping since early 2014 and is on the verge of replacement.
Tl;dr - GT75 is a turd but Anandtech sees what they want to see. I have to wonder if Ryzen is going to be reviewed the same way.
JohanAnandtech - Friday, February 24, 2017 - link
7zip is indeed a bad indicator for server performance, but at the time, we only had access to a virtual machine on top of a POWER8 with 2 GB of RAM and we thought it might give us a first glimpse of what the P8 was capable off.As time progressed, we understood that is mostly a TLB/latency sensitive benchmark. So it has no place in a server oriented article, it is mostly interesting to discuss micro arch details.
Ian Cutress - Friday, February 24, 2017 - link
Anandtech has different editors focusing on different areas - Johan on Server, I'm on CPU, Matt on mobile, etc. Feel free to reach out via email if you have suggestions for us.Kevin G - Friday, February 24, 2017 - link
This isn't the best showing of POWER8. Those chips need robust cooling to keep their clock speeds up to be competitive. The 1U form factor does place a lot of constraints on the design.As for the Tyan system itself, I'm kinda of surprised that they went with the Centaur buffer that uses DDR3 as IBM has reportedly been shipping buffers that support DDR4 for nearly half a year now. That'd lower power consumption greatly, though likely not enough to be competitive with Intel on a system level performance/watt metric. Moving to DDR4 would give the system a massive increase in memory capacity as 128 GB LR DDR4 DIMMs are shipping with 256 GB LR DIMMs on the horizon. Using 256 GB DIMMs, a system like this would support 8 TB which is a lot for a 1U server.
Considering the internals of the system I'm not surprised but a secondary PSU option would have been nice, even if it was external. PSU redundancy is remarkably common, even for 1U systems.
I'd also be worried about IO performance on this system with all the networking and SATA ports hanging off of a single PCIe uplink to the CPU.
I do agree with the conclusion that POWER9 looks to be very promising. The nice thing is that IBM is going to be offering both the SMT4 and SMT8 cores in both types of sockets (essentially four different dies!).
ddriver - Saturday, February 25, 2017 - link
Form factor wont change the facts - it is a power, it is too expensive, and it is too slow. Power sounds great on paper, but it doesn't seem to deliver in practice.Kevin G - Tuesday, February 28, 2017 - link
Form factor does matter when it changes the cooling system which in turn can invoke thermal throttling.Even on the x86 side of things, half wide 2U servers are popular as they can use larger fans despite having the same effective density as a full width 1U server. The increased air flow into a chassis is great for keepings cools and helps maintain high turbo levels for performance.