Comments on: Data center high density vs. low density: Is there a paradox?

By: Markfontecchio

Markfontecchio — Thu, 28 May 2009 12:49:12 +0000

Thanks to TonyHarvey for his response, which is the same one that I got. I also have a few more details. When you order the BladeCenter, HP can configure the system with fewer than six power supplies if the configuration wouldn’t require all the power supplies to be installed. Maximum density is often less than 5KW, or about one-third the amount I had said in my initial post. HP also has a feature that allows the end user to set a power cap on the enclosure.

If anything, these power figures go against the power-density paradox, but four chasses of fully stocked blade servers could still have a maximum 20KW of power consumed, and that is still a massive cooling challenge, as Bullock has said.

By: TonyHarvey

TonyHarvey — Wed, 27 May 2009 17:11:07 +0000

EST412: You are correct the c7000 actually load shares in an N+N configuration so all power supplies will be active, but 3 of the power supplies are effectively reserved for redudnancy. So the max theoretical power consumption is 2400 x 3 or 7200W., but as Shambruch correctly points out this just the power supply cpapacity. Not the actual power usage of that enclosure.

The actual power usage of the enclosure is very dependant on what is installed in the enclosure – as an example a c7000 could have 1 – 16 blades each blade could 1 – 2 CPUS and anywhere from 1 to 18 DIMMs. All of this can make a huge difference. In shameless self promtion mode I have started a series posts about this on the HP [A href="http://www.communities.hp.com/online/blogs/eyeonblades/default.aspx"]Eye On Blades [/A]Blog

By: Shambruch

Shambruch — Tue, 26 May 2009 17:03:12 +0000

EST412: Yes you are mostly correct. The unit requires only three of the six power supplies to be operational in order for it to run, however, all six are running during normal operation and consuming power in a load balancing scheme. At the end of the day, a more accurate figure for this blade chassis running at peak load would be 6-7kW not 14kW. The nameplate rating used in the article shows maximum possible transient current draw ( like the initial momentary burst required to start up the system) and not maximum steady state operational current draw, which is sometimes less than half of the nameplate rating.

By: Shambruch

Shambruch — Tue, 26 May 2009 16:49:35 +0000

I see a couple of issues with this article. First, the power loads given for the IT equipment are nameplate ratings, meaning these are the numbers the manufacturers are forced to publish to meet UL requirements and are not indicative of the unit’s steady state power draw even at peak load. To determine realistic cooling requirements, a derated figure should be used. Secondly, when comparing 1 rack of blade servers to six racks of standard 1U servers, some thought must be given to the fact the rack of blade servers will not stand in isolation. In other words, if you implemented a rack of blade servers, you wouldn’t leave the next 5 racks empty in order to offset the power draw from the one rack. Therefor we can assume that the data center will fill up with exponentially increasing heat loads due to the consolidation the blade systems provide. This lends to Mr. Bullock’s theory of diminishing returns based on the footprint consumed by increasing power and cooling infrastructure.

By: Markfontecchio

Markfontecchio — Tue, 26 May 2009 15:04:16 +0000

Est412: I’m honestly not sure of the answer to your questions. I’ve put in a request to HP to get it, and as soon as I know, I’ll let you know. Thanks,

Mark

By: Est412

Est412 — Sun, 24 May 2009 10:40:46 +0000

Mark, you’ve said: “… Each c7000 chassis demands 6 x 2,400 watts of power, or 14,400 watts…”
Aren’t a half of 6 chassi’s PSUs work as the hot spare PSUs? So real maximum power demand of c7000 chassis is 7,200W? Or i’m wrong?

P.S. Sorry for my English…

By: MBullock

MBullock — Wed, 25 Feb 2009 20:59:29 +0000

Thanks Mark, I agree with your points and don't see as being contradictory to my original blog or the [A href="http://transitionaldata.com/insights/TDS_DC_Optimization_Power_Density_Paradox_White_Paper.pdf "]power density paradox [/A] white paper from which it is based. Unfortunately it is difficult to cover everything in a 500 word blog and my intent was just to create awareness for those who have less grasp of the thermodynamics involved. Yes, higher density systems will pay dividends (recover space and more efficiency per CPU) until you bump up against limits of currently available power and cooling. Once you approach these limits, there are some steps you can take to incrementally improve the situation – some of which are covered in the whitepaper (ultrasonic humidification, VFDs, economizers, etc.). There are also some more exotic approaches that do not have the same ROI. The primary point I was trying to make is simply as you increase density, at some point, you will need more power and more cooling to continue to expand. And as you do, this will cause your total space to increase as you account for additional support space – more CRACs, larger capacity backup generators, fuel, etc. If your CRACs must be positioned on the raised floor, this will also decrease your usable space. My firm, [A href="http://www.transitionaldata.com"]TDS [/A]understands the impact that high density has on power / cooling efficiency - and usable space. We have recently earned one of our clients a $454,000 rebate check from NSTAR which I’ll write about in my next [A href="http://advice.cio.com/blogs/data_center_expert"]blog on CIO.com[/A].