Low Power Server CPUs: the energy saving choice?
by Johan De Gelas on July 15, 2010 4:54 AM EST- Posted in
- IT Computing
How useful are low power server CPUs?
We were quite a bit surprised that the lower power CPU did not return any significant energy savings compared to the X5670. Intuition tells you that the best server CPUs like the X5670 only would pay off in a high performance environment (for example an HPC server). But human intuition is a bad guide when dealing with physics. Cold hard measurements are a much better way to make up your mind. And all our measurements point in the same direction: the fastest Xeon offers a superior performance/watt ratio in a typical virtualization consolidation scenario.
You could argue that the X5670 is quite a bit more expensive; a server equipped with a dual X5670 will indeed cost you about $900 more. We admit: our comparison is not completely accurate price wise… as always we work with the CPUs that we got in the lab. But a typical server with these CPUs, 64 GB and some accessories will set you back $9000 easily. The 2.8 GHz Xeon X5560 is hardly 4% slower than the X5670, and will probably show the same favorable performance/watt ratio. And if you place a X5560 2.8 GHz instead of a L5640 2.26 GHz, you only add $200 dollar to a $8k-$9k server. That is peanuts, lost in the noise of the TCO calculation. So the question is real: are the "Low power Xeons" (L-series) useless and should you immediately go for the X-series?
Defeated as it may be, the L5640 can still play one trump card: lower maximum currents. Over the period of our 70 minutes of testing, we decided to take a look at maximum power. To avoid that any extreme peaks would muddle up the picture, we used the 95th percentile.
Let us focus on the “balanced” power plan. The L5640 makes sure power never goes beyond 231 W, while the peak of the X5670 is almost 20% higher. As a result, a rack of low power Xeon will be able to keep the maximum current consumed lower. You could consider the low power Xeon L5640 a “power capped” version of Xeon X5670. In many datacenters you pay a hefty fine if you briefly need more than the amp limit you have agreed upon. So the low power Xeon might save you money by guaranteeing that you never need more than a certain amperage.
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Zstream - Thursday, July 15, 2010 - link
It kills the AMD low power motto :(duploxxx - Thursday, July 15, 2010 - link
lol, all that you can say about this article is something about AMD. Looks like you need an update on server knowledge, Since the Arrival of Nehalem Intel has the best offer when you need the highest performance parts and when using Low power parts which give still the best performance. Since MC arrived things got a bit different mostly due to aggressive price for all mid value but still a favor to intel parts for highend and L power bins. Certainly in the area of virtualization AMD does very wellWhat is shown here should be known to many people that design virtual environments, Virtualization and low power parts don't match if you run applications that need cpu power and response all the time, L series can only be very useful for a huge bunch of "sleeping" vm's.
Interesting would be to compare with AMD, but 9/10 both low power and high power intel parts will be more interesting when you will only run 1 tile, the huge core amount lower ipc advantage will loose against the higher ipc/core of intel in this battle.
Zstream - Thursday, July 15, 2010 - link
Excuse me? I am quite aware of low power consuming chips. The point AMD has made in the past four to five years is that low power and high performance can match Intel's performance and still save you money. I have been to a number of AMD web conferences and siminars were they state the above.MrSpadge - Thursday, July 15, 2010 - link
Not sure if you're being sarcastic here, as it's obvious AMD would tell you this.
But regarding the actual question: you'd be about right if you compared K8 or Phenom I based Opterons with Core 2 based ones. And you'd be very right if you compared them to Phenom II. However, the performance of these Intels is being held back by the FSB and FB-DIMMs and power efficiency is almost crippled by the FB-DIMMs. But Nehalem changed all of that.
MrS
duploxxx - Friday, July 16, 2010 - link
4-5 years.... Nehalem was launched q12009 since then all changed. Before that Xeon parts suffered from FBDimm powerconsumption and FSB bottleneck and that is why AMD was still king on power/performance and was able to keep up with max performance. Nehalem was king, Istanbul was able to close the gap a bit but missed raw ghz and had higher power needs due to ddr2, again MC parts leveraged back this intel advantage and now there is a choice again, but L power still is king to Neh/Gulf.Penti - Saturday, July 17, 2010 - link
It invalidates low power versions of AMDs also. That's he's point I would believe.stimudent - Thursday, July 15, 2010 - link
Not really.If there can't be two sides to the story or a more diverse perspective, then it should not have been published. Next time, wait a little longer for parts to arrive - try harder next time.
MrSpadge - Friday, July 16, 2010 - link
A comparison to AMD would have been nice, but this article is not Intel vs. AMD!It already has 2 side: high power vs. low power Intels. And Johan found something very important and worthy of reporting. No need to blur the point by including other chips.
MrS
Zstream - Thursday, July 15, 2010 - link
I know we have the VMware results but could someone do an analysis on AMD / INTEL chips?For instance I can get a 12 core AMD chip or a 6 core/12 HT chip from Intel. Has anyone done any test with Terminal Servers or Real world usage of a VM (XP Desktop) with core count?
I would think that a physical 12C vs 6C impacts real world performance by a considerable large amount.
tech6 - Thursday, July 15, 2010 - link
Great work Anandtech - it's about time someone took the low power TCO claims to task.