Step by Step
- Sep 15, 2012
Calculating a baseline level of server energy consumption and tracking progress are important elements in evaluating costs and benefits likely secured through various efficiency-boosting investments and strategies. As Pierre Delforge, senior engineer with the Natural Resources Defense Council’s Center for Energy Efficiency Standards, is quick to point out, even owner-users and net lease occupants that pay their own utilities in many cases have little clue how much juice gets consumed—and wasted—in server closets.
While various measurement methods might apply in an office building server closet, the NRDC recommends starting by calculating an approximate IT load. This entails multiplying the facility’s Uninterruptible Power Supplies load factor (specified on a UPS load indicator) by the corresponding UPS power rating (available online).
The next step is to have a competent electrician install logging meters on the server closet’s air-conditioning circuit breakers. Adding this cooling load to the IT load should provide a decent estimate of the server closet’s overall energy use. If measuring air-conditioning use proves problematic, one reasonable rule of thumb is that one watt of cooling is necessary for every watt of IT load, so doubling the IT load should at least approximate the actual total energy use.
In addition, a lot of businesses relinquish simple savings by neglecting to regularly eliminate “ghost servers”—equipment that had hosted applications that have been decommissioned or are otherwise no longer in use. These as well as other rarely used servers too often continue running full time, and should be switched off to eliminate wasted energy.
It is not unusual for one of every three servers essentially to serve no purpose, related corporate energy consultant Mark Bramfitt. And even servers that host important applications during working hours can be shifted to low-power modes requiring a fraction of the energy. Modern technology keeps them ready to respond at normal power levels as needed.
But in many cases the most effective technological strategy small and midsize businesses can implement to save on server closet energy costs is virtualization—consolidating multiple applications from several underutilized (single-application) servers into appropriately programmed servers.
A heavily loaded server uses far less energy than multiple, lightly loaded servers, Bramfitt stressed. And it is not unreasonable to expect that 10 or even 15 underutilized servers can be consolidated into a powerful virtualized host server—which no doubt handles a bigger energy load than a standard server but cut can cut overall server energy consumption by 50 percent or more.
Smaller, more load-balanced virtualized server arrays will also likely generate noteworthy equipment procurement and maintenance savings and less heat, reducing air-cooling costs, Delforge noted.
Add it all up, and consolidating even as few as five servers into a virtualized host can cut server closet energy consumption by as much as 80 percent, according to NRDC calculations. And to aid in maintaining an optimal server utilization rate as an operation’s IT needs grow, hardware vendors typically offer software that tracks utilization over time.
Likewise, the latest generation of servers is substantially more energy efficient than predecessor models. The EPA’s EnergyStar program alone has established high efficiency standards for servers and numerous other classes of
“My rule of thumb is that any server older than three years is overdue for decommissioning and a move to a virtualized environment,” Delforge stated. “But I’m sure it can often be cost effective to do it even more frequently—both financially and from a carbon (emissions) perspective.”
Even absent a big virtualization push or equipment upgrade, some businesses should be able to cut into server closet energy consumption by boosting the efficiency of space cooling systems. Indeed, in most cases, at least 10 percent of energy consumed by server closets is devoted just to cooling the air, the NBI/Ecova researchers discovered.
One painless possibility: adjusting a given closet’s temperature setting per ASHRAE recommendations. And depending on the space size, it might also make economic sense to upgrade cooling equipment, such as perhaps installing variable-speed drives for fans and economizers.
This sidebar accompanies “Cleaning Cluttered (Server) Closets,” which appears in the October 2012 issue.