Facebook recently released a detailed report on their energy consumption and carbon footprint: Facebook’s Carbon and Energy Impact. Facebook has always been super open with the details behind there infrastructure. For example, they invited me to tour the Prineville datacenter just prior to its opening:

· Open Compute Project

· Open Compute Mechanical System Design

· Open Compute Server Design

· Open Compute UPS & Power Supply

Reading through the Facebook Carbon and Energy Impact page, we see they consumed 532 million kWh of energy in 2011 of which 509m kWh went to their datacenters. High scale data centers have fairly small daily variation in power consumption as server load goes up and down and there are some variations in power consumption due to external temperature conditions since hot days require more cooling than chilly days. But, highly efficient datacenters tend to be effected less by weather spending only a tiny fraction of their total power on cooling. Assuming a flat consumption model, Facebook is averaging, over the course of the year, 58.07MW of total power delivered to its data centers.

Facebook reports an unbelievably good 1.07 Power Usage Effectiveness (PUE) which means that for every 1 Watt delivered to their servers they lose only 0.07W in power distribution and mechanical systems. I always take publicly released PUE numbers with a grain of salt in that there has been a bit of a PUE race going on between some of the large operators. It’s just about assured that there are different interpretations and different measurement techniques being employed in computing these numbers so comparing them probably doesn’t tell us much. See PUE is Still Broken but I Still use it and PUE and Total Power Usage Efficiency for more on PUE and some of the issues in using it comparatively.

Using the Facebook PUE number of 1.07, we know they are delivering 54.27MW to the IT load (servers and storage). We don’t know the average server draw at Facebook but they have excellent server designs (see Open Compute Server Design) so they likely average at or below as 300W per server. Since 300W is an estimate, let’s also look at 250W and 400W per server:

· 250W/server: 217,080 servers

· 300W/server: 180,900 servers

· 350W/server: 155,057 servers

As a comparative data point, Google’s data centers consume 260MW in aggregate (Google Details, and Defends, It’s use of Electricity). Google reports their PUE is 1.14 so we know they are delivering 228MW to their IT infrastructure (servers and storage). Google is perhaps the most focused in the industry on low power consuming servers. They invest deeply in custom designs and are willing to spend considerably more to reduce energy consumption. Estimating their average server power draw at 250W and looking at the +/-25W about that average consumption rate:

· 225W/server: 1,155,555 servers

· 250W/server: 1,040,000 servers

· 275W/server: 945,454 servers

I find the Google and Facebook server counts interesting for two reasons. First, Google was estimated to have 1 million servers more than 5 years ago. The number may have been high at the time but it’s very clear that they have been super focused on work load efficiency and infrastructure utilization. To grow the search and advertising as much as they have without growing the server count at anywhere close to the same rate (if at all) is impressive. Continuing to add computationally expensive search features and new products and yet still being able to hold the server count near flat is even more impressive.

The second notable observation from this data is that the Facebook server count is growing fast. Back in October of 2009, they had 30,000 servers. In June of 2010 the count climbed to 60,000 servers. Today they are over 150k.


James Hamilton
e: jrh@mvdirona.com
http://blog.mvdirona.com / http://perspectives.mvdirona.com