Power Usage Effectiveness & Efficiency Flashcards
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Read the first 7 Power Usage Effectiveness & Efficiency flashcards as text
What is the relationship between server power supply efficiency (80 PLUS ratings) and PUE?
Answer: PSU efficiency is included in the IT equipment denominator and does not affect PUE
PSU losses are part of IT equipment power (the denominator), so while better PSUs reduce total energy use, they do not directly change the PUE ratio.
A hyperscale operator installs on-site solar panels that supply 2 MW to the facility's 10 MW total load (IT load 8 MW). How should this affect PUE calculation per Green Grid guidance?
Answer: PUE is calculated the same way regardless of energy source; source attribution does not change the PUE ratio
PUE measures power consumption ratios, not energy sources; the Green Grid standard does not subtract on-site generation from total facility power in the PUE formula.
Hot-aisle/cold-aisle containment primarily improves PUE by achieving which effect?
Answer: Preventing hot exhaust air from mixing with cold supply air, allowing higher cooling supply temperatures
Containment eliminates hot/cold air mixing, allowing cooling systems to supply warmer air at higher setpoints while still maintaining safe server inlet temperatures.
Which scenario represents a 'PUE gaming' practice that inflates efficiency reporting?
Answer: Offloading non-critical IT loads to co-located facilities during measurement periods
Temporarily removing IT load (denominator) without reducing overhead (numerator) during measurement periods artificially improves the reported PUE ratio.
What role does power distribution unit (PDU) efficiency play in a data center's PUE?
Answer: PDU losses appear in total facility power but not IT equipment power, so higher PDU efficiency directly improves PUE
PDU transformer and switching losses add to total facility overhead in the PUE numerator while the IT equipment power at the server remains in the denominator.
According to The Green Grid, what is the recommended minimum sampling frequency for an annualized PUE measurement?
Answer: Every 15 minutes or less, accumulated over 12 months
The Green Grid recommends continuous metering at 15-minute intervals or finer for a full year to capture seasonal, daily, and load-variation effects on PUE.
A data center achieves PUE 1.3 at full load but PUE 1.8 at 20% load. What design approach would best address this partial-load inefficiency?
Answer: Deploying modular, scalable infrastructure that can be powered down as load varies
Modular 'pay-as-you-grow' infrastructure allows unused modules to be decommissioned, keeping active systems near their efficient operating points even at low IT loads.