Data Center Design IssuesBill Tschudi, LBNLWFTschudi@lbl.gov

Design IssuesDesign Issues

IT equipment loadIT equipment load RedundancyRedundancy Data center airflowData center airflow Environmental conditionsEnvironmental conditions ZoningZoning Isolating hot and coldIsolating hot and cold

IT Equipment LoadIT Equipment Load

Predicting IT loadsPredicting IT loads– Over sizing, at least initially, is commonOver sizing, at least initially, is common– Implement modular and scalable approachesImplement modular and scalable approaches

IT loads can be controlledIT loads can be controlled– Power supply optionsPower supply options– Server efficiencyServer efficiency– Software efficiency (Virtualization, MAID, etc.)Software efficiency (Virtualization, MAID, etc.)– Redundancy and back-up powerRedundancy and back-up power– Low power modesLow power modes

Reducing IT load has a multiplier effect Reducing IT load has a multiplier effect

ASHRAE Prediction of Intensity ASHRAE Prediction of Intensity TrendTrend

RedundancyRedundancy

Understand what redundancy Understand what redundancy costs – is it worth it?costs – is it worth it?

Different strategies have Different strategies have different energy penalties (e.g. different energy penalties (e.g. 2N vs. N+1)2N vs. N+1)

Redundancy in electrical Redundancy in electrical distribution always puts you down distribution always puts you down the efficiency curvethe efficiency curve

Measured UPS Efficiency

Redundant Operation

Air Flow RequirementsAir Flow Requirements

Typically, much more air is circulated Typically, much more air is circulated through computer room air conditioners through computer room air conditioners than is specified by manufacturers due than is specified by manufacturers due to mixing and short circuiting of airto mixing and short circuiting of air

Computer manufacturers now provide Computer manufacturers now provide ASHRAE data sheets which specify ASHRAE data sheets which specify airflow and environmental requirementsairflow and environmental requirements

Evaluate airflow from computer room air Evaluate airflow from computer room air conditioners compared to server needsconditioners compared to server needs

Visualizing Air FlowVisualizing Air Flow

Computational Fluid Computational Fluid Dynamics (CFD) modeling Dynamics (CFD) modeling

Temperature sensor Temperature sensor networksnetworks

Infrared thermographyInfrared thermography

Environmental ConditionsEnvironmental Conditions

ASHRAE - consensus ASHRAE - consensus from all major IT from all major IT manufacturers on manufacturers on temperature and temperature and humidity conditionshumidity conditions

Recommended and Recommended and Allowable ranges of Allowable ranges of temp and humiditytemp and humidity

Air flow requiredAir flow required

Other ASHRAE ResourcesOther ASHRAE Resources

Four books Four books published—more published—more in preparationin preparation

Temperature Guidelines – Temperature Guidelines – at The Inlet to IT Equipmentat The Inlet to IT Equipment

ASHRAE TEMPERATURE GUIDELINES

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Degrees F

ASHRAE Allowable Maximum

ASHRAE Allowable Minimum

ASHRAE Recommended Maximum

ASHRAE Recommended Minimum

Humidity Guidelines— Humidity Guidelines— at The Inlet to IT Equipmentat The Inlet to IT Equipment

ASHRAE HUMIDITY GUIDELINES

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% Relative Humidity

ASHRAE Allowable Maximum

ASHRAE Allowable Minimum

ASHRAE Recommended Maximum

ASHRAE Recommended Minimum

ZoningZoning

Some IT equipment (e.g. storage) Some IT equipment (e.g. storage) requires tighter controlrequires tighter control

Don’t penalize the whole center Don’t penalize the whole center for a few pieces of equipmentfor a few pieces of equipment

Different zones should be Different zones should be providedprovided

Isolating Hot and ColdIsolating Hot and Cold

Energy intensive IT equipment needs Energy intensive IT equipment needs good isolation of “cold” inlet and “hot” good isolation of “cold” inlet and “hot” dischargedischarge

Computer room air conditioner airflow Computer room air conditioner airflow can be reduced if no mixing occurscan be reduced if no mixing occurs

Overall temperature can be raised in Overall temperature can be raised in the data center if air is delivered to the data center if air is delivered to equipment without mixingequipment without mixing

Coils and chillers are more efficient Coils and chillers are more efficient with higher temperature differenceswith higher temperature differences

Best Scenario— Best Scenario— Isolate Cold and HotIsolate Cold and Hot

70-75ºF

95-100ºF

Another Isolation SchemeAnother Isolation Scheme

Fan Energy SavingsFan Energy Savings – 75%– 75%

If mixing of cold supply If mixing of cold supply air with hot return air air with hot return air can be eliminated-can be eliminated-fan speed can be fan speed can be reducedreduced

Better Temperature Control Better Temperature Control Can Allow Raising the Can Allow Raising the Temperature in The Entire Data Temperature in The Entire Data CenterCenter

Cold Aisle NW - PGE12813

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6/13/2006 12:00 6/14/2006 0:00 6/14/2006 12:00 6/15/2006 0:00 6/15/2006 12:00 6/16/2006 0:00 6/16/2006 12:00

Time

Temperature (deg F)

Low

Med

High

Baseline Alternate 1

Setup

Setup

Alternate 2

ASHRAE Recommended Range

Ranges during demonstration

Take AwaysTake Aways

IT equipment loads can be improvedIT equipment loads can be improved Air flow delivered by computer room air Air flow delivered by computer room air

conditioners must satisfy IT equipment conditioners must satisfy IT equipment Different redundancy strategies have Different redundancy strategies have

different efficienciesdifferent efficiencies Operating within ASHRAE guidelines can save Operating within ASHRAE guidelines can save

energy energy Modern IT equipment is not sensitive to Modern IT equipment is not sensitive to

humidityhumidity Isolating hot and cold can improve efficiencyIsolating hot and cold can improve efficiency

website: website: http://hightech.lbl.gov/datacenters/http://hightech.lbl.gov/datacenters/