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

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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

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

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Open Secret: Datacenter electrical costs are skyrocketing…

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$ B

I L

L I

O N

S

M I

L L

I O

N S

O F

S E

R V

E R

S

…fueled by an explosion in power / heat densities

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Industry groups + vendors propose a wide range of solutions

IT 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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Source: EYP Mission Critical Facilities Inc., New York

But first, we need to understand the problem…

Typical Real-World Energy Allocation

in Today’s Datacenter

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

“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=

8

PUE is extremely valuable as a broad efficiency ratio…

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

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… and has become a de facto standard metric

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

Sun Microsystems

Microsoft Google

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

A relative measure of your plant versus your IT equipment

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.

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Example: Henry’s Super Awesome DatacenterTM (SAD)

• 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.)

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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

PUE =Power UsageEffectiveness

=Total Facility Power

IT Equipment Power

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Green Grid recognizes that PUE is not a panacea

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

Proposed: Three “levels” of PUE sophistication

DCP =DatacenterProductivity

=“Useful Work”

Total Facility Power

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

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

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… including environmental information

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

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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

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!

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Gather data beyond PUE to enable tangible efficiency actions

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!

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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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Click Here to Learn About Raritan Power Solutions

Thank You!

Henry Hsu • Raritan, Inc.

Solutions Consulting, Datacenter Efficiency

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