HP ProLiant BL660c ISS Technology Update, Volume 8, Number 3 - Page 6

PUE and DCE-Useful metrics for overall data center efficiency

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ISS Technology Update Volume 8, Number 3 PUE and DCE-Useful metrics for overall data center efficiency IT and facilities engineers can use two metrics to evaluate data center energy efficiency: Power Use Efficiency (PUE) and Data Center Efficiency (DCE). PUE and DCE are not intended to measure the efficiency of specific power and cooling systems within data center infrastructures. Rather, they are useful as "field" metrics to quantify overall data center efficiency. As illustrated in Figure 3-1, PUE is the total power delivered to the facility divided by the net power that goes directly to the IT equipment. PUE can be used by an organization to benchmark its data center operations against the industry. It also offers a simple metric for determining compliance with governmental energy policies. DCE-the inverse of PUE-is an alternative metric that is represented as a percentage. The DCE of a non-optimized data center may be 60%, while an optimized data center could have a DCE of 75% or higher.1 Research by the Uptime Institute2 indicates that 85% of data centers consume 2 kW for each kW used by IT equipment, with only a small portion going to power conditioning/conversion. This energy use results in a PUE of 3, and yields a DCE of 33 percent, meaning that only one-third of facility power is consumed by IT equipment (Figure 3-1 right). Data centers with a PUE of 3 or greater typically have a grossly over-provisioned cooling system. Over-provisioning increases capital and recurring expenses and decreases utilization and efficiency, which results in a higher total cost of ownership (TCO). Consequently, alternate strategies are required to isolate root causes of inefficiency and provide remedial solutions. These strategies range from adopting the latest best practices for high-density computing platforms to creating a management layer that enables consolidation and an infrastructure that can dynamically provision power and cooling resources as needed. Figure 3-1. PUE is the total data center load divided by the power that goes directly to IT equipment. DCE is the inverse percentage of PUE. 1 Aebischer, B. Eubank, H., Tschudi, W., "Energy Efficiency Indicators for Data Centers," International Conference on Improving Energy Efficiency in Commercial Buildings "IEECB'04", 21 - 22 April 2004, Frankfurt (Germany). DCE is equivalent to CEE (Coefficient of Energy Efficiency). 2 Belady, C., Malone, C., "Metrics to Characterize Data Center & IT Equipment Energy Use," Digital Power Forum, Richardson, TX (September, 2006). 6

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ISS Technology Update
Volume 8, Number 3
6
PUE and DCE—Useful metrics for overall data center efficiency
IT and facilities engineers can use two metrics to evaluate data center energy efficiency: Power Use Efficiency (PUE) and Data
Center Efficiency (DCE). PUE and DCE are not intended to measure the efficiency of specific power and cooling systems within
data center infrastructures. Rather, they are useful as “field” metrics to quantify overall data center efficiency.
As illustrated in Figure 3-1, PUE is the total power delivered to the facility divided by the net power that goes directly to the IT
equipment. PUE can be used by an organization to benchmark its data center operations against the industry. It also offers a
simple metric for determining compliance with governmental energy policies.
DCE—the inverse of PUE—is an alternative metric that is represented as a percentage. The DCE of a non-optimized data center
may be 60%, while an optimized data center could have a DCE of 75% or higher.
1
Research by the Uptime Institute
2
indicates
that 85% of data centers consume 2 kW for each kW used by IT equipment, with only a small portion going to power
conditioning/conversion. This energy use results in a PUE of 3, and yields a DCE of 33 percent, meaning that only one-third of
facility power is consumed by IT equipment (Figure 3-1 right).
Data centers with a PUE of 3 or greater typically have a grossly over-provisioned cooling system. Over-provisioning increases
capital and recurring expenses and decreases utilization and efficiency, which results in a higher total cost of ownership (TCO).
Consequently, alternate strategies are required to isolate root causes of inefficiency and provide remedial solutions. These
strategies range from adopting the latest best practices for high-density computing platforms to creating a management layer
that enables consolidation and an infrastructure that can dynamically provision power and cooling resources as needed.
Figure 3-1. PUE is the total data center load divided by the power that goes directly to IT equipment. DCE is the inverse
percentage of PUE.
1
Aebischer, B. Eubank, H., Tschudi, W., “Energy Efficiency Indicators for Data Centers,“ International Conference on Improving Energy
Efficiency in Commercial Buildings “IEECB’04”, 21 - 22 April 2004, Frankfurt (Germany). DCE is equivalent to CEE (Coefficient of Energy
Efficiency).
2
Belady, C., Malone, C., "Metrics to Characterize Data Center & IT Equipment Energy Use," Digital Power Forum, Richardson, TX
(September, 2006).