PUE Reconsidered

PUE ReconsideredUtility + Limitations of PUE / DCiE as a Datacenter Efficiency

Metric

PUE Reconsidered

• Historical Basis for PUE – what is the problem?

• Strengths of PUE Metric – what does it measure?

• Weaknesses of PUE Metric – what does it omit?

• Bottom Line: How to be Strategic About Datacenter Efficiency

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Utility + Limitations of PUE / DCiE as a Datacenter Efficiency Metric

Open Secret: Datacenter electrical costs are skyrocketing…

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$ B

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…fueled by an explosion in power / heat densities

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Industry groups + vendors propose a wide range of solutionsIT equipment Cooling & moving air

► virtualization

► power save mode

► consolidation

► upgrade technology

► decommission servers

► move apps/jobs to virtualized servers and shut down servers

► batch processing during off-peak

► avoid overcooling

► minimize humidification

► reduce air mixing via hot/cold air separation

► blanking plates to minimize recirculation

► raised floor grommets to reduce bypass airflow

► optimize floor layout (CFD)

► closely couple supply and returns to the load

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But first, we need to understand the problem…

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Source: EYP Mission Critical Facilities Inc., New York

Typical Real-World Energy Allocation

in Today’s Datacenter

…so The Green Grid proposed PUE as a benchmark in Feb’07

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“Green Grid Data Center Power Efficiency Metrics: PUE and DCiE”; by Christian Belady, et. al.; www.thegreengrid.org

PUE =Power UsageEffectiveness

=Total Facility Power

IT Equipment Power

DCiE is the exact same thing, but expressed as an inverse:

DCiE =Datacenter

InfrastructureEfficiency Total Facility Power

IT Equipment Power=

1

PUE=

PUE is extremely valuable as a broad efficiency ratio…

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PUE =Power UsageEffectiveness

=Total Facility Power

IT Equipment Power

PUE =1 MW

0.5 MW= 2.0

“My total facility consumes 2x the power of the IT equipment load.”

DCiE =PUE

1= 0.5

“Roughly 50% of the power in myfacility is used to power IT equipment.”

EXAMPLE: Typical 1MW Facility

… and has become a de facto standard metric

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Sun Microsystems

Microsoft Google

• Dueling Press Releases (e.g. Google and Microsoft)• EPA Datacenter “Energy Star” Program• Department of Energy (DOE) “DCPro” Tool and Survey

It’s critical to understand what PUE is, and what it is not!

A relative measure of your plant versus your IT equipment

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PUE =1 MW

0.5 MW= 2.0

• Resilience: Tier I / II / III / IV architecture?

• Trending: How does my efficiency change as IT load changes?

• Diversity: Heterogeneous versus homogenous IT load?

• Utility: Are the servers themselves being used well?

Does not (in and of itself) address:

In short, it does not benchmark the efficiency of the IT component.

Example: Henry’s Super Awesome DatacenterTM (SAD)

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• 1000 servers

• Equipment from every AFCOM sponsor ever

• Located in Reykjavik, Iceland (max temp = 55)

• Placed outdoors under a tented roof

• 24/7/365 operation

PERFECT PUE OF 1.0 !!Every kilowatt is used to power servers. No energy “wasted”.

• Servers completely underutilized

• No critical resilience whatsoever

• No business value or practicality

• Real-world evaluation = complete waste of energy

• All servers dedicated full-time to HenryAndHisCat.com(Video site featuring footage of me playing with my cat.)

None of the proposed IT initiatives (on left, below) improve PUE

IT equipment Cooling & moving air

►virtualization►power save mode►consolidation►upgrade technology►decommission servers

extra savings on cooling

►move apps/jobs to virtualized servers and shut down servers

►batch processing during off-peak

►avoid overcooling►minimize humidification►reduce air mixing via hot/cold air

separation►blanking plates to minimize recirculation►raised floor grommets to reduce bypass

airflow►optimize floor layout (CFD)►closely couple supply and returns to the

load

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PUE =Power UsageEffectiveness =

Total Facility Power

IT Equipment Power

Green Grid recognizes that PUE is not a panacea

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Proposed: In the long-term, create a business-oriented metric

Proposed: Three “levels” of PUE sophistication

DCP = DatacenterProductivity

=“Useful Work”

Total Facility Power

To solve the real problem, we need to measure it…

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Uptime Institute, “4 Metrics That Define Data Center Greenness”

… including environmental information

15Source: ASHRAE, “Thermal Guidelines for Data Processing Environments”

Real-world user examples where better info = energy savings• World’s Largest Networking Company

• Goal: reduce 25% carbon emissions by 2012• Problem: test labs account for more than 80% of corporate energy consumption• Solution: automate shutdown of test equipment when not in use;

provide detailed, comprehensive energy savings data for all labs in enterprise.

• Largest European Bank• Goal: quantify exact power costs for each business application in datacenters• Problem: no reliable, real-time energy data exists for individual servers • Solution: rack PDU’s that provide detailed power + environmental monitoring data for

each receptacle in the cabinet.

• World’s Largest Software Company• Goal: Provide state-of-the-art data center for customers to perform live integration

testing of application suites.• Problem: Need to reboot servers remotely; and understand real-time power

consumption of each customer’s test configurations• Solution: high-security intelligent rack PDUs with remote switching and energy metering.

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Gather data beyond PUE to enable tangible efficiency actions

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Important Solution Attributes:• Open standards / vendor agnostic

• Trended information over time

• Energy data (kwh), not just current (amps)

• Energy data per IT device (not just for rack)

• Product configs to fit all rack densities

• Make sure facilities is happy (UL489)

• Use what you have!

Gather data beyond PUE to enable tangible efficiency actions

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Important Solution Attributes:• Open standards / vendor agnostic

• Trended information over time

• Energy data (kwh), not just current (amps)

• Energy data per IT device (not just for rack)

• Product configs to fit all rack densities

• Make sure facilities is happy (UL489)

• Use what you have!

Summary• PUE is valuable (and widespread) as a high-level metric

• You must understand the pros / cons of PUE to properly evaluate industry, vendor, and press claims

• PUE is not sufficient to improve efficiency tactically

• Datacenters can only be optimized when the energy chain is fully understood / instrumented:

• the appropriate measurements;• at a sufficient level of detail;• trended over time;• easily interpreted;• at incremental CapEx cost;

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Thank You!

Henry Hsu • Raritan, Inc.

Solutions Consulting, Datacenter Efficiency

Henry.Hsu@raritan.com • (732) 764-8886 x1273