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Linux captures the “green” flag, beats Windows 2008 power saving measures
// How we did it
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Greener pastures for Web server farms?
// Virtualization thwarts green OS initiatives
// NOC infrastructure may thwart green OS ideals

Virtualization thwarts green OS initiatives

By Tom Henderson, Network World Lab Alliance , Network World , 06/09/2008
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There are certain popular system architectures that transcend the operating system and will turn your efforts to build a green network operating system brown, figuratively speaking.

Hypervisors, the underlying technology used to permit consolidation of software servers into virtual machines, uniformly push CPU pedals to the floor and never, ever let up.

Hypervisors thwart CPU green initiatives (especially ones where the operating system plays a role in conserving overall energy consumption by throttling back the CPU during low activity periods) because they subscribe to the get-the-best-performance-per-watt-used school of thought.

The hypervisors we tested from VMware (ESX 3.X), XenSource Xen, and Microsoft's Virtual Server (not Hyper-V, which isn't yet released) all prohibit the ability for the CPU/chipsets to reduce speed or go into 'green mode' as long as there's a virtual machine guest running atop the hypervisor — regardless of operating system flavor.

Hypervisors allocate system resources as specified by administrative constraints imposed on VM guest operating systems and applications. The action of actively monitoring and allocating specified resources generates a lot of work for the CPU. Hypervisor system clock ticks, resource controls, combined with host VM guest operating system ticks, simply prevent CPUs from resting, and therefore saving power.

The argument in favor of hypervisors as an energy-saving measure is that you can run multiple guest operating systems and their applications on a single hardware platform when they had previously been housed on mutliple, aged servers.

< Return to main story: Linux captures the “green" flag, beats Windows 2008 power saving measures >

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Comments (6)
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Basic math skillsBy Paul on March 3, 2009, 1:48 pm24 servers consuming an average of 200W each via use of power saving features: 4.8kW 3 servers consuming 700W running VMware with 8 (good, stable number) virtual...

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I dont think soBy Anonymous on October 2, 2008, 1:21 pmI dont have a profound knowledge in virtualization but i guess the vital things which is needed for a virtualized OS is CPU, RAM and Diskspace. So here the author...

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VM & Power savingsBy David123456 on June 11, 2008, 5:18 pmI agree. Very little thought was put into this article. Looks like something written quickly and added as filler. David

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Absolutely Wrong !!!! How can this be published ???By bigaldover on June 11, 2008, 11:22 amHow could such rubish be published. By this authors math, our orginization is better to have 25 idling servers than one server running at 25-30 %. I can't believe...

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The opposite is trueBy Anonymous on June 10, 2008, 11:30 pmIn fact virtualization is a big driver of energy savings in the data center. PG&E, my local utility in Silicon Valley, offers significant financial inncentives for...

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