Drastically Reducing Server Energy Costs

The first automated system capable of turning servers on and off according to need in order to prevent the energetic waste of idle units has been developed by Portuguese scientists. In the last year, the free software has saved the energy equivalent of five tons of CO₂ emissions in just the 200 computers of the Interdisciplinary Complex of Lisbon University.

The program is called SPIRIT, and its potential is huge, as Carlos Reis and Jorge Pacheco, the two scientists behind the project, explain: “Used worldwide, SPIRIT could result in yearly savings equivalent to the energy produced by a 1000 MW Nuclear Power Station, or, in other words, a reduction of about five million tons of CO₂ emissions every year” (the emissions of 6.5 millions London-NY flights). The software was developed at the University of Minho and the University of Lisbon in Portugal and was presented at the Fifth International Conference on Software Engineering Advances ICSEA 2010, where it won a best paper award.

Twenty million servers are driving the “information age” in which we live, with numbers expected to increase to a staggering 120 million by 2020, according to increasingly worried organizations like The Climate Group and Global e-Sustainability Initiative. This constant growth implies massive amounts of energy usage and CO₂ production and, in fact, one percent of the total CO₂ world emissions are already being tracked back to computer servers. By comparison, the aviation industry is responsible for two percent of the total.

These numbers have not passed unnoticed, and the need to control the impact of the computing industry on the environment has become a priority of governments, public groups and even the industry in itself. Large companies like Microsoft and Google have moved (amid much publicity) some of their larger data centers close to green energy sources — such as electric dams — an option, though, that very few can afford.

Other approaches being exploited include renting — where big companies rent computational power to smaller ones, with a recent example being WikiLeaks renting space (and being kicked out of it) on Amazon — and sharing – where home users lend their computers’ idle time to analyze data for big researching organizations. In sharing, the most well-known example is probably SETI@Home, a NASA program that looks for signs of extraterrestrial intelligence. But, if these practices can reduce energetic waste, they do not diminish the industry energetic footprint or its environmental impact.

An alternative is the use of “natural” ways to cool down servers — cooling counts for about 45 percent of all the energy used by servers — by using nearby water resources or, in colder climates, the outside air. Although this can produce remarkable savings, again, it is an option that only a few can exploit, and new methods to reduce the energetic and environmental costs of computers have to be found.

And it’s here that the software SPIRIT steps in.

Most of the electricity usage and CO₂ release in computing is linked to big companies and research centers with massive computational needs. And these normally use parallel computing, a system where large projects are divided into small tasks that can then be run in parallel on the many computers of the server, substantially accelerating the project’s resolution. While fast, this approach is not energetically efficient. When the number of tasks is not enough to occupy all computers, those remaining free continue to spend energy while waiting for new tasks. This waste is particularly worrying when we consider that servers normally run 24 hours per day, 365 days a year. To make things worse studies have found that, on average, only 16 percent of the computers in a server are busy at any given time. (So, basically 84 percent of them are doing nothing most of the time.)

So, how does SPIRIT help? In parallel computing, when all computers are busy, new tasks are added to a queue where they wait for the next available computer. SPIRIT, which is installed in the servers’ mother node (that controls and connects all the computers of the group) works by responding to this queue — turning off all idle computers when the queue is empty and turning on the necessary computers as new tasks are detected. As the queue is checked very regularly, no task is left waiting for long. This means that there is no real loss of efficiency despite the remarkable savings of energy.

If, normally, 84 percent of the computers of the 20 million servers now existing are idle, and that these servers are already responsible for around one percent of the whole world energy usage (a value predicted to increase 16 percent every year) it is easy to see the potential of SPIRIT.

The energy savings in Lisbon — five tons of CO₂ in just one year — were obtained on two servers with extremely high levels of usage — 60 percent against the normal average of 16 percent — and with just 100 computers each.

Under the shadow of climate change, energy waste and CO₂ emissions have to be dramatically reduced. SPIRIT is an extraordinarily simple, but effective solution. It is freely available at http://www.ciul.ul.pt/~ATP/SPIRIT/.