PUE Reconsidered - AFCOM (MI), July 2009

PUE Reconsidered Utility + Limitations of PUE / DCiE as a Datacenter Efficiency Metric 29 July 2009

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 Henry Hsu • Raritan, Inc. Solutions Consulting, Datacenter Efficiency Henry.Hsu@raritan.com • (732) 764-8886 x1273

Open Secret: Datacenter electrical costs are skyrocketing… $ 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

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

But first, we need to understand the problem… 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 “ Green Grid Data Center Power Efficiency Metrics: PUE and DCiE”; by Christian Belady, et. al.; www.thegreengrid.org PUE = Power Usage Effectiveness = Total Facility Power IT Equipment Power DCiE is the exact same thing , but expressed as an inverse: DCiE = Datacenter Infrastructure Efficiency Total Facility Power IT Equipment Power = 1 PUE =

PUE is extremely valuable as a broad efficiency ratio… PUE = Power Usage Effectiveness = 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 my facility is used to power IT equipment.” EXAMPLE: Typical 1MW Facility

… 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

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.

Example: Henry’s Super Awesome Datacenter TM (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
Servers completely underutilized
No critical resilience whatsoever
No business value or practicality
Real-world evaluation = complete waste of energy
PERFECT PUE OF 1.0 !! Every kilowatt is used to power servers. No energy “wasted”.
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 PUE = Power Usage Effectiveness = Total Facility Power IT Equipment Power 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

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 = Datacenter Productivity = “ Useful Work” Total Facility Power

To solve the real problem, we need to measure it… Uptime Institute, “4 Metrics That Define Data Center Greenness”

… including environmental information Source: 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 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 rack PDU’s with remote switching and energy metering.

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!

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;

Questions / Comments / Discussion

Thank You! Henry Hsu • Raritan, Inc. Solutions Consulting, Datacenter Efficiency Henry.Hsu@raritan.com • (732) 764-8886 x1273

PUE Reconsidered - AFCOM (MI), July 2009

by Henry Hsu on Jul 30, 2009

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