Two Slam Dunks for Reducing Data Center Energy Bills

Author: Dennis Bouley

June 2008

The two important sources of power consumption in data centers are IT equipment and physical infrastructure (power, cooling, and lighting) equipment.  In a typical data center, less than half the electricity coming in actually makes it to the computer loads.  The rest is consumed by the physical infrastructure.

This article focuses on two approaches that have a great impact on reducing electrical consumption in the data center: IT load reduction and physical infrastructure rightsizing.  Execution of the first approach (load reduction) can, by itself, positively impact the goal of the second approach (rightsizing).  The idea is that less computer load requires less power and cooling to support it.  

Sensible IT Load Reductions
Most data centers have old IT systems that remain operational for archival or research purposes.  In fact, some operating application servers have no users. It is useful to inventory these systems and to create a retirement plan for them.  These systems can be taken off line and powered down.  Use of server power management tools will allow a server to operate in a low energy “sleep” mode even if the server is not physically retired.  If the data center requirements change, these systems can be brought back online with minimal effort. A power consumption reduction of up to 20% is possible in such a “retirement” scenario.

The major way that new server technologies can help reduce power consumption is when consolidation of applications on servers is used to reduce the total server count, or when servers are virtualized.  Virtualization of servers results in a dramatic reduction of IT power requirements.  The savings from avoided electrical consumption over a 10 year period can be substantially greater than the cost of the server itself (go to http://www.tools.apc.com to calculate your virtualization benefit).  

Physical Infrastructure Rightsizing
The second biggest hitter in terms of energy savings is the right-sizing of the physical infrastructure systems.  Most users do not understand that fixed losses are present in the power and cooling systems whether the IT load is existent or not.  The bigger the physical infrastructure install base, the bigger the fixed losses.

Installations with light IT loads often experience physical infrastructure fixed losses that exceed the IT load.  Whenever the physical infrastructure system is oversized, the fixed losses become a larger percentage of the total electrical bill.  For a typical system that is loaded at 30% of rating, the electrical cost per kW of IT load is approximately $2,300 per kW per year.  If the system were right-sized to the load, the electrical cost per kW of IT load falls to approximately $1,440 per kW per year which is a 38% savings in electrical costs.  
These are the potential savings for a specific example; actual savings will vary and will be less for non-redundant systems (go to http://www.tools.apc.com to calculate your data center’s efficiency benefit).  

The compelling economic advantages of IT load reduction and physical infrastructure right-sizing can also serve as a basis for calculating overall data center efficiency.  Data center infrastructure efficiency (DCiE) can be expressed as a ratio of watts to the IT load / watts to the data center.  If 100 watts of power enter the data center and only 60 of those watts make it to the IT load, then that data center is 60% efficient (60/100 = 60%).  Reductions in IT load (via retirement and virtualization) and rightsizing of physical infrastructure (via scalable, modular systems) are the two biggest ways to move up the data center efficiency percentage.

For more information please contact CDW Berbee, John Uchaker at 513-677-4119.  CDW Berbee, drawing on strategic partnerships with Cisco, IBM and Microsoft and the far-reaching experience of its hundreds of engineers, has assisted clients with a full range of technology solutions.  For other information, please visit www.berbee.com.