So Christmas is over and we are all looking somewhat ruefully at our waist lines and hoping to get back in shape before the summer rolls around. Data center operators have another problem, how to cut some of the fat out of their data centers and get their energy budget in shape for the new year. Just this week I was asked the question “How can I trim a million KW-hours energy consumption this year?” That sounds like a daunting, but worthy exercise, a million KW-hours sounds like a huge number, but at 8-cents a kilowatt-hour trimming 1 million kilowatt-hours would save $80,000 dollars in the first year (of course, price/KW-hour varies considerably by location, so your mileage may vary.)
The first point to note is that while the number seems huge, that simply reflects the size of the customer’s data center, the real question is “what changes will have the most impact on energy consumption?” So here’s some tips on how you can reduce energy consumption in the data center:
- Reduce the amount of equipment in use: The quickest way to significant savings is to cut back the amount of equipment in use through technologies such as server virtualization. Let's assume that 1/3rd of the servers in a data center are suitable candidates for virtualization and that on average a 5:1 consolidation ratio is possible (and that’s a conservative estimate for the consolidation ratio.) A datacenter with a thousand servers would be able to virtualize 333 of them, replacing those 333 physical servers with just 67, a net reduction of 266 physical servers. Now lets assume that these original servers were 1U pizza-box servers each consuming 300 watts of power, and that the new servers are bigger (to accommodate the extra memory, processors etc) and consume 600 watts of power, the net power saving is almost 60 kilowatts. Such an approach would also reduce power consumption for cooling by a similar margin (assuming 1:1: ratio between power consumed by equipment and power consumed by cooling.) This step alone would save a million KW-hours, throw in some improved storage management practices and deduplication for data and the energy savings quickly pile up.
- Get rid of old equipment: Some data centers continue to use equipment until it finally dies, that can mean servers that are 5 or even 10 years old (I've seen even worse cases). These servers are energy and space hogs and deliver very little work for the power consumed compared to a more modern system, especially if the more modern system is combined with server virtualization.
- Improve power distribution: This can take the form of a number of improvements and upgrades. For example old UPS equipment is substantially less efficient (i.e. wastes more energy) than modern UPS systems, replacing the old UPS could yield a 5-10% reduction in energy consumption. Also minimize the number of voltage conversions between the power as delivered by the utility and the power consumed by the equipment, i.e. bring high-voltage power as close to the racks as possible. Data centers in the US still using 120V AC to power equipment in the racks, need to take a long hard look at switching to 240V AC, the equipment doesn’t care and it will save energy and simplify the wiring.
- Cooling improvements: Air-side economizers can deliver big savings, especially in more temperate climates. Assume roughly half the energy consumed by the data center is used for cooling, and that the airside economizer can function for half the year, then potential savings in energy consumption are pretty obvious. Also improve hot-aisle/cold aisle separation or implement fully ducted hot-air removal from racks can increase cooling efficiency inside the data center.
The big lesson here is that the quickest payback for reducing energy consumption is to reduce the amount of equipment in the data center and opportunity presented by maturing server virtualization technology is too good to pass up! The downside is that to save money in the long term, you’ll have to spend some money in the short term.
Posted by: Nik Simpson