Eye on Blades Blog: Trends in Infrastructure
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A Blade Kill

In April, SPEC updated their server power benchmark to allow results for blade servers, and now HP has released its first blade result. 
HP just published a SPECpower_ssj2008 result for the HP BL280c G6 server blade.  It's the top score for a blade.   I talked to Kari Kelley, the BL280c product manager, and she called it a "solid kill."

The kill comment made more sense after Kari explained she played division-1 volleyball while at Texas A&M. "A kill is a good thing," she assured me.

SPEC didn't open up that benchmark to blades until their SPECpower_ssj2008 V1.10 came out this spring.  For a multi-node system (like a blade infrastructure), the benchmark has to be run with a full set of servers -- so a c7000 enclosure filled with 16 BL280c servers in HP's case. Power is measured at the AC line voltage source, while the test itself monitors throughput and power usage at various performance levels, including periods when the servers are 100% idle.  HP has written this whitepaper that talks more about the benchmark methodology.

For the BL280c G6 server, the overall result was 1877 ssj_ops/watt.   Full details here.  For full details about kills, along with sets and spikes, you'll have to talk to Kari.

SPEC and the benchmark name SPECpower_ssj are trademarks of the Standard Performance Evaluation Corporation. The latest SPECpower_ssj2008 benchmark results are available on the SPEC website at http://www.spec.org/power_ssj2008.

Applications Matter - What Affects Server Power Consumption: Part 2

 How does the application you are using and what it is doing affect the power consumption of system.

The first thing that everyone looks at when talking about power consumption is CPU utilization.  Unfortunately CPU utilization is not a good proxy for power consumption and the reason why goes right down to the instruction level. Modern CPUs like the Intel Nehalem and AMD Istanbul processors have 100s of millions of transistors on the die.  What really drives power consumption is how many of those transistors are actually active.  At the most basic level an instruction will activate a number of transistors on the CPU, depending on what the instruction is actually doing a different number of transistors will be activated. So a simple register add, for example, might integer add the values in two registers and place the result in a third register.  A relatively small number of transistors will be active during this sequence.  The opposite would be a complex instruction that streams data from memory to the cache and feeds it to the floating point unit activating millions of transistors simultaneously.

Further to this modern CPU architectures allow some instruction level parallelization so you can, if the code sequence supports it, run multiple operations simultaneously. Then on top of that we have multiple threads and multiple cores.  So depending on how the code is written you can have a single linear sequence of instructions running or multiple parallel streams running on multiple ALUs and FPUs in the processor simultaneously

Add to that the fact that in modern CPUs the power load drops dramatically when the CPU is not actively working, idle circuitry in the CPU is placed in sleep modes, standby or switched off to reduce power consumption.  So if you're not running any floating point code, for example, huge numbers of transistors are not active and not consuming much power. 

This means that application power utilization varies depending on what the application is actually doing and how it is written.   Therefore depending on the application you run you will see massively different power consumption even if they all report 100% CPU utilization.  You can even see differences running the same benchmark depending on which compiler is used and whether the benchmark was optimized for a specific platform or not and the exact instruction sequence that is run.

The data in graph below shows the relative power consumption of an HP BladeSystem c7000 Enclosure with 32 BL2x220c Servers.  We ran a bunch of applications and also had a couple of customers with the same configuration who wre able to give us power measurements off their enclosures.  One key thing to note is that the CPU was pegged at 100% for all of these tests, (except the idle measurement obviously).

As you can see there is a significant difference between idle and the highest power application, Linpack running across 8 cores in each blade.  Another point to look at is that two customer applications, Rendering and Monte Carlo, don't get anywhere close to the Prime95 and Linpack benchmarks in terms of power consumption.

It is therefore impossible to say what is the power consumption of server X and comparing it to server Y unless they are both running the same application under the same conditions.  This why both SPEC  and the TPC have been developing power consumption benchmarks that look at both the workload and power consumption to give an comparable value between different systems.

SPEC in fact just added Power Consumption metrics to the new SPECweb2009 and interesting enoughly the two results that are up there have the same performance per watt number, but they have wildy different configurations, absolute performance numbers and absolute wattage numbers. So there's more to performance per watt than meets the eye.

The first part of this series was Configuration Matters

Datacenter Power Allocation


I was going to add some more details to Chuck's post on how a blade server powers on, but I got sidetracked by a brilliant post from Mike Manos of Digital Realty on the real basics of what is going with power in your datacenter.

What Mike is explaining, far better than I could, is how power gets used up and reserved in your datacenter by breaker sizes, redundancy and natural tendency of the facility management to be conservative when allocating power to servers, and as he says they have good reason to be.  If they plug in a device that causes a breaker to trip taking down multiple servers - it's their butts that are on the line.

He raised a good question about why the faceplate label, the label on power supply that indicates the max power input, is so high that most facilities managers are comfortable de-rating it by 20% - 30%.  Well the reason is explained in part by my post on how configuration affects power consumption; the power supply is designed to deal with maximum configured load.  The range from a minimum configured load for a 2 socket server e.g. 1 Low Power CPU, 1 or 2 DIMMs, 1 x SSD drive and no PCI cards, to a maximum configured load e.g. 2 x 120W or 130W CPUs, 12 or 18 DIMMs, 8 x 15K RPM Drives, 3 x PCI Cards including a 200W graphics card, is huge and that’s just one server.  The example I use in the Configuration Matters post shows a difference of over 1kW across an enclosure.  Talk to any power supply designer and you'll find out that they are just as conservative as any facility manager (and unappreciated) and for pretty much the same reasons.  Who gets blamed when you run a high power program like Prime95 or Linpack and the server shuts down because the power supply couldn’t deliver enough juice.

That’s why HP came up with the common slot power supply design for rack mount servers. It allows you to size the power supply for the actual configuration you will be using rather than just stuffing a 1200W power supply in every server.

 This has two great consequences:

  1. It reduces the amount of trapped or stranded power by reducing the amount the power that the facility manager has to allocate to a given server.

  2. It increases your power supply efficiency, reducing energy wasted.  All power supplies have an efficiency curve that for servers at low outputs has a low efficiency and gets to peak efficiency at about 35% - 50% 65% load (Got corrected by one of the engineering team on this.  Must remember in future to check my numbers). Remember most servers have redundant power supplies and in the HP case they load share so the PSU can only ever exceed 50% load in the event of a redundancy failure.

This does add complexity to your buying decision, now you have to pick the power supply you need based on your configuration.  That's why we created the HP Power Advisor to help with that decision.  Of course you can still just use a 750W or 1200W PSU for every server if you want to, but you won't be running as efficiently as you could.

One area though where I must respectfully disagree with Mike is in his comments on Power Capping. I agree that is a technology that has huge potential in the datacenter to allow your facilities team to recover that trapped capacity, but I disagree that it is not ready for prime-time.

HP delivered our first version of power capping in 2007. This was relatively slow acting and was really only good for controlling the average power consumption of a server. This was great if you had a cooling issue on your datacenter and wanted to control the heat output of your servers as heat is largely related to average power of the server, but you couldn’t use it to protect circuit breakers.

In November 2008 HP introduced Dynamic Power Capping with circuit breaker protection.  This is a hardware based solution that can respond to changes in power consumption in less than 500ms and because it’s a hardware solution it’s operating system and application independent.  This is supported on all G6 servers, most blade servers and selected G5 rack-mount servers.  When run on an HP Blade Enclosure you gain additional capabilities; the Onboard Administrator can manage the blade server caps to optimize the performance of the enclosure. It will change the blade level power caps so that busier blades get more power and less busy blades will get less power while maintaining the enclosure level power cap so you can protect your breakers.

For a demonstration of this on the rack mount servers showing how we deliver circuit breaker protection see this video with “Professor” Alan Goodrum and for more information Dynamic Power Capping go to http://www.hp.com/go/powercapping


Taking a closer look at the "Power On" capabilities for blade chassis


Some of our Blade Specialists give us the workings of the BladeSystem "Power switch" . David gives us these words of wisdom.

"I've always referred to the "power switch" on the front of the blade not as a power switch but a " may I?" switch.  When actuated, the blade asks the OA if there is enough available power to power on and spin up the drives (the act of powering on takes a higher load than steady state operation).  If at that moment there is not enough power, the blade pauses and tries again in a moment (there's an algorithm in there that determines the actual length of the pause so that if several blades had asked for power at the same time, they don't all use the same delays and end up in deadlock).  If after requesting power several times (sorry, don't know how many) there still isn't enough power, it will stop trying. If a blade has not been successfully turned on, the command can be issued again.

Net/net:  the blade infrastructure is designed to prevent more power demand than is available.  The illustration above is equally valid if power-on is initiated from power switch, OA/iLO command, or via Wake-on-LAN..."

And Tony added in his experience.

"David is correct but there are some subtleties about how the server will respond.  On a cold boot - insertion, enclosure power-up, etc. if Automatic Power-On is set, then the server will retry power on requests if they get denied.

Power-On commands like the power button or iLO Virtual Power/OA commands are one time things - if the request fails it will not be retried.  Therefore as David said the application needs to be able to detect if a server has powered on after the request is issued."

Hope this helps.




Least Favourite Question

I'm sitting here thinking about writing my first Blog post and trying to come up with something to say.  So I figured I'd start by trying to answer one of my least favourite questions (and before you all start to correct my spelling I'm not originally from the USA) and explain why it's so hard to answer.

The Question: "So much power does a blade enclosure use?"

The answer: "It depends."

What does it depend on? Everything.

How many Blades and which Blades do you have in the enclosure, which CPUS, are they the 50W, 60W, 80W, 95W or 120W versions, how many DIMMs and what size and rank are they, which mezzanines are installed, which Interconnects are installed, how many fans, what's the ambient temperature, what applications are running and how heavily loaded are they?

Even if you gave me all this information I still couldn't answer with any degree of accuracy, those final two items applications and application load really do have such a huge impact it makes it almost impossible to give the right answer. The best that I could do would be to give the maximum and minimum power usage based on that configuration and say you'll be somewhere in-between those two values.

In the next few posts I'll go into some detail about this starting with the affect hardware configuration has on power consumption.

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About the Author(s)
  • More than 25 years in the IT industry developing and managing marketing programs. Focused in emerging technologies like Virtualization, cloud and big data.
  • I am a member of the Enterprise Group Global Marketing team blogging on topics of interest for HP Servers. Check out blog posts on all four Server blog sites-Reality Check, The Eye on Blades, Mission Critical Computing and Hyperscale Computing- for exciting news on the future of compute.
  • I work within EMEA HP Servers Central Team as a launch manager for new products and general communications manager for EMEA HP Server specific information. I also tweet @ServerSavvyElla
  • HP Servers, Converged Infrastructure, Converged Systems and ExpertOne
  • WW responsibility for development of ROI and TCO tools for the entire ISS portfolio. Technical expertise with a financial spin to help IT show the business value of their projects.
  • I am a member of the HP BladeSystem Portfolio Marketing team, so my posts will focus on all things blades and blade infrastructure. Enjoy!
  • Luke Oda is a member of the HP's BCS Marketing team. With a primary focus on marketing programs that support HP's BCS portfolio. His interests include all things mission-critical and the continuing innovation that HP demonstrates across the globe.
  • Global Marketing Manager with 15 years experience in the high-tech industry.
  • 20 years of marketing experience in semiconductors, networking and servers. Focused on HP BladeSystem networking supporting Virtual Connect, interconnects and network adapters.
  • Working with HP BladeSystem.
  • Greetings! I am on the HP Enterprise Group marketing team. Topics I am interested in include Converged Infrastructure, Converged Systems and Management, and HP BladeSystem.
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