DCeP: Data Center energy Productivity
Since the 2007 EPA Report to Congress on Server and Data
Center Energy Efficiency was published, much has been
written on improving energy efficiency in critical
facilities. Many of the conversations, until now, have
addressed efficiency without productivity. While PUE and
DCiE focus primarily on infrastructure- the mechanical and
electrical systems that support the data center-are they
enough to brand an entire data center efficient?
A comprehensive efficiency grade must include the
productivity of the data center-the "useful work" performed
by IT equipment. A new metric called Data Center energy
Productivity (DCeP) incorporates both the infrastructure and
the IT equipment when evaluating data center energy
efficiency.
What is DCeP?
DCeP is a sophisticated metric that quantifies useful work
compared to the energy it requires. It can be calculated for
an individual IT device or a cluster of computing equipment.
DCeP = Useful Work Produced / Total Data Center Energy
Consumed over time
Like PUE and DCiE, time is important to this measurement.
DCeP has an "assessment window" where useful work and energy
are compared relative to a user-defined time limit.
Calculating DCeP
The work of a data center is unique to its operator. For
this reason, it's difficult to prescribe a universal
productivity metric. DCeP itself is a work in progress, and
the Green Grid is currently evaluating several alternatives
to measure useful work in different ways. Both DCeP and
these proxies may require functionality or instrumentation
not included in off-the-shelf IT hardware.
Useful Work
Useful work depends on two readings: the tasks performed by
the hardware and the assessment window. Tasks should be as
specific as possible, while the assessment window "should be
no shorter than about 20 times the mean run time of any of
the tasks initiated in the assessment window" (The Green
Grid, 2008). A data center should define both figures
according to their workload and business model.
The Green Grid proposes the following equation for useful
work:
(Sum of all tasks * Value of the task) * Time Based Utility
Function * Absolute Time of Completion
This equation acknowledges that some tasks are more
important than others. Some may be mission critical (task
value) while others may involve a response time that's an
integral part of an SLA (time-based utility function).
To simplify the calculation, the task value and utility
function can be assigned as (1), meaning that all tasks are
weighted the same. From there, useful work boils down to the
number of tasks (jobs, transactions) carried out by the
hardware during the assessment window.
Total Data Center Energy Consumed
This calculation involves two figures: the kWh of the
hardware in question and the PUE of the facility. If the
hardware and infrastructure are efficient, this reading will
improve.
Total Energy Consumed = kWh of energy consumed by hardware *
data center PUE
To arrive at this answer, a facility must have an efficiency
benchmarking program for PUE/ DCiE and the ability to
measure power at the device level. While not all data
centers have this capability, new software, the latest rack
power products, and power meters can all track power
consumption at the device level. This consumption in kWh is
multiplied by the PUE figure to arrive at the total energy
consumed during the assessment window
DCeP Going Forward
DCeP represents a necessary progression in metrics, for the
efficiency conversation must include productivity.
By measuring PUE/DCiE consistently, users can identify and
remediate infrastructure deficiencies through sealing cable
cutouts, tuning hot/cold aisles, and adjusting temperatures.
Small improvements in physical infrastructure go a long way,
and users should begin the process with the initial PUE/DCiE
benchmark.
With these improvements in place, users can then focus on
the output of their data center and the productivity of
their compute systems. This process may open doors to
consolidation, virtualization, and the decommissioning of
idle, older compute platforms.
The mantra of the moment is right-sizing. Calculating DCeP
allows users to right-size virtual and physical
infrastructures to support business needs.
About 42U
Since 1995, 42U has been a leader in providing
data center efficiency
solutions for data center and facilities managers. Our vendor and technology
agnostic approach leverages our best-practice expertise in monitoring, airflow
analysis, power, measurement, cooling, and best-of-breed efficiency technologies
to help data center managers improve energy efficiency, reducing power consumption
and subsequently lowering energy costs.
This work is licensed under a
Creative Commons Attribution-No Derivative Works 3.0
Unported License.
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