Power In The Data Center
You Have to Measure Before You Can Improve
By Ed Higgins
Power Monitoring is the first step to savings in your Data Center.
As global competition intensifies, companies are increasingly turning
to technology to help turn mountains of data into a competitive edge.
With soaring energy prices and the need for round-the-clock data center
services, enterprises must find ways to increase energy efficiency and
reduce costs. In addition, escalating power consumption by large data
centers and the population in general means additional power is not
always available to expand computing services. Although power is
becoming the most significant cost in running a data center, most data
center managers lack the tools to accurately measure power consumption.
All of these factors, along with a growing concern for environmental
stewardship, are forcing the need for better power-monitoring
technologies.
The cost of power is increasing. Power is now the single largest
operating cost in the data center. The impending Carbon tax are forcing
companies to truly understand their energy use patterns to reduce power
usage due to increased costs associated with energy consumption. With
today’s limited IT budgets, any energy savings means more money for
revenue generating activities that can help bolster the bottom line.
Power failures are expensive and detrimental to business. The high
cost of data center downtime due to power failure is another threat that
plagues data center managers. Any downtime of the equipment in data
centers supporting today’s global companies and organizations can mean
millions of dollars in lost revenue, as well as withering customer
confidence. Data loss or corruption resulting from power-related issues
is equally damaging to a company’s revenue and reputation.
Why It’s Important to Monitor Power
You need to measure it before you can fix it. Analysts continue to
rank energy efficiency as the number one concern of data center owners
and operators. The truth is, however, you simply can’t improve
something, especially energy efficiency, if you’re not measuring it.
Energy efficiency projects often pay for themselves in energy savings,
but if you don’t know how much energy you’re using and how much it
costs, it is very difficult to justify new technologies and best
practices or to assess the savings of those new methods. Without a
baseline and then continued measurements, it is impossible to determine
where to optimize, to evaluate the results of the optimizations, or to show the
improvements to management, government agencies, or customers. In
addition, you need to be able to identify energy consumption peaks and
lows and determine how they relate to operations and key internal and
external events (such as marketing campaigns, accounting cycles, and
changing weather patterns) to enable you to adequately plan for these
events.
A number of organizations, including The Green Grid and the Uptime
Institute, are working to develop standards to help companies become
more energy efficient. The Green Grid’s Power Usage Effectiveness (PUE)
metric is becoming a standard for data center energy efficiency, but PUE
cannot be reasonably determined if energy consumption cannot be
measured. Measuring at the device plug (after all of the power
conversion, switching, and conditioning is performed) is the best way to
calculate PUE. Finally, measuring at the device plug is sometimes the
only way to accurately measure power usage in a data center—particularly
if the data center shares power with other areas in the building.
By measuring power usage you can:• Identify potential cost savings and set goals
• Identify current power costs and set a baseline
• Implement efficiency improvement projects
• continuously measure to determine success
• Accurately bill departments and tenants
• Balance 3 phase power systems
Data center managers need to understand it to work with it. In most
data center today, data center management and facilities management are
still handled by two different departments, which means data center
managers operate without fully understanding the ramifications of
infrastructure changes.
Another reason to monitor power is to avoid costly downtime and loss
of data. Systems consuming an inordinate amount of energy might be
signalling a performance problem. On the other hand, inadequate power
can cause stability problems. The ability to monitor power usage
provides yet another tool to help data center staff actively solves
potential problems, thereby possibly saving millions of dollars in
losses.
The Benefits of Power Monitoring and Management
Increase profitability with lowered energy and operating costs. Even a
small drop in energy consumption can deliver substantial cost savings
over time.
Ensure accurate chargeback. Collocation providers charge tenants for
energy usage. Monitoring power provides accurate data on usage, making
it easier to compute charges. Clients are more likely to accept these
charges if they are provided with accurate statements. A full accounting
of energy usage can also help departments understand how effectively
they are using the compute resources they purchase. Power usage data is
also enabling service providers to implement a different pricing model
determined by such categories as power factor. Tenants with legacy
equipment having a bad power factor are charged at a higher rate for
excess power usage. This will increase the Collocation provider’s green
credentials.
When you understand power usage in the data center, you can also
begin to intelligently balance phases on your 3 phase power system to
optimize energy use and reduce costs. There are a number of benefits
that make efficient load phase balancing a worthwhile objective. One
such instance would be increased feeder capacity. The loading on a
feeder section is synonymous with the most heavily loaded phase and, in
the case of significant imbalance, feeder capacity is used
inefficiently. Balancing between phases tends to equalize the phase
loading by reducing the largest phase peak while increasing the load on
the other phases. This equates to releasing feeder capacity that can be
used for future load increases without reinforcing feeder conductors.
Additionally, phase balancing reduces feeder losses because any phase
peak reduction affects the losses for the phases as the square of the
current magnitude. A feeder section with 1-ohm resistance that has phase
currents of 50A/100A/150A will have 35kW in losses. When balanced at
100A/100A/100A, the loss reduces down to 30kW. The same effect is even
more evident in the reduction of reactive power losses because the X/R
ratio of most feeder sections is greater than 1.
Phase balancing also improves the voltage on a feeder by equalizing
the voltage drops in each phase along the feeder. This released feeder
capacity provides more reserve loading capacity for emergency loading
conditions. It is realistic to assume that the benefits in improved use
of feeder capacity and improved voltage quality are of more significance
than the value of loss reduction except when loading is already high.
Typically, balancing is accomplished by selecting the phase of the
supply for each load so that the total load is distributed as evenly as
possible between the phases for each section of feeder.
In summary, the only way to achieve power savings in the data center is to first actively measure current and power at as many granular points as is reasonably possible. From there, you will begin to see the areas of low-hanging fruit (typically the fruits represent 20%) for which you can implement strategies for cost reduction, whether this be consolidation, virtualization, elimination, or advances tactics such as integral power-capping vehicles which instruct systems to "slow-down" when right conditions are met. Only the best DCIM solutions can provide the real-time monitoring capability to give you this insight.
I hope you enjoyed this article, and hope it was helpful.
Until next time,
Ed
