ESTIMATES

*Note: The illustrative pictures on the right are too small for any meaningful usage. Please see the chart below, which provides a relatively clear picture, though based on many estimates and guesses. This is a good as gets.*
 
Getting a picture of a vital technology
Cloud computing is driving a worldwide trend for more and bigger data centers. But where are these data centers? How big are they? Who runs them? What are the growth figures?  How much energy is consumed by these centers?
 
The exact numbers for most of these questions are hard to get. Many of the large firms are secretive about their infrastructure.
 
The best we can get are some hard figures mixed with many estimates. However, some information stay unknown, such as how many servers are running at big banks, government agencies and in other organizations.
 
Still, some data and estimates can be extracted and they are still helpful to get a picture of what is going on. 

 
1. How many data centers?
The best source here is the "Data Center Map". It provides a quick overview of data centers and cloud computing farms. One shortcoming is that it is a bit unclear whether they really have all data centers or just the ones that have been listed by the editors or manually by users. Furthermore, corporate data centers are not listed, e.g. the ones set-up by large companies like Google, Intel or Microsoft (see other entries below). 
 
Regarding its accuracy, the website states this: 

"The site was launched in October 2007 and is today the most comprehensive site of this kind, covering more than 1500 facilities from more than 60 countries. In May 2009 the site was relaunched with a lot of new functions and expansion of services covered. Data Center Map is free to use for both clients and providers, and is financed primarily by advertising and commission fees for connecting providers with new clients." (Source: http://www.datacentermap.com)

2. How many cloud centers?
The recent outage of a cloud data center in Dublin, Ireland, affecting both Amazon and Microsoft cloud services, brought out one interesting fact: Companies from Europe, who are governed by certain compliance rules can not replicate their data to US servers. This (big) hole in the cloud offering landscape should be somehow closed through another cloud-orientated data center or must be considered as a scenario by such customers. 
 
http://www.datacentermap.com/cloud.html
 
3. How many servers?
To be correct, this actually is not about the number of servers in use. More precisely, it is asking how many machines are running around the world. The best compilation can be found at Data Center Knowledge. They compiled and updated the most extensive list we found so far. Figures listed are based on hard facts (such as numbers from company reports), quite a few estimates and a Netcraft Server count. The article was originally published in 2009 and has been updated in August 2011, so the estimates should be as close to reality as you can currently get. 
 
The biggest number of servers is estimated to be in use at Google, current figures saying that about 900.000 are in use. This figure can be higher and - equally - considerably lower should Google has found a way to manage server output in new ways.
 
4. How many servers does Google have?
The exact number of servers in use for the search engine is unclear. What is known is that Google perfected a system to use standard PCs instead of supercomputers. A good account of Google's handling of data centers, re-routing of IP adresses and other tech trivia has been compiled by Royal Pingdom.
 
http://royal.pingdom.com/2008/04/11/map-of-all-google-data-center-locations/
 
5. How many servers can one admin manage?
This is interesting, too. Again estimates only, though it is an interesting and relevant question to know when a datacenter would be over- or understaffed. According to an article by Rich Miller (2009), the admin/server ratio varies from company to company. Quoting a Facebook vice president, at that time the social network had 230 admins looking for about 30.000 servers. Since then Facebook has invested heavily into a new data center and even outsourced the information for the set-up of that facility. Microsoft is said to have one admin "between 1.000 and 2.000 servers". 
 
As one commenter on that article noted, the number of admins might go down due to further automation, but at the same time might grow if there are more applications to look after. So, the sheer number of servers seems to be a lesser indicator to estimate the needed people to keep them running. 
 
6. How high is the power consumption of these data centers?
There are fears that the heavy investments into these data centers might result in growing power consumption worldwide. In fact, some of the newest data centers are placed right beside big power plants or sources of water electricity. According to an updated analysis by Jonathan Koomey the consumption of energy has gone up since 2005, but has not grown to levels projected in an earlier report. For the world, the consumption of energy by data centers around is 1,1 percent.

Quote
 
"...the new report indicates that electricity used by global data centers in 2010 remained relatively modest. “Electricity used in global data centers likely accounted for between 1.1 percent and 1.5 percent of total electricity use, respectively. For the U.S. that number was between 1.7 percent and 2.2 percent... In an earlier paper, Mr. Koomey reported that the power used by servers in data centers represented about 0.5 percent of world electricity consumption in 2005. When cooling and auxiliary infrastructure were included, that figure was about 1 percent, he wrote. The worldwide demand for data center power in 2005 was equivalent to the output of about 17 1,000-megawatt power plants.” (Source: New York Times, 2011)
 
 
Original report: Jonathan Koomey. 2011. Growth in Data center electricity use 2005 to 2010. Oakland, CA: Analytics Press. August 1
 

7. What kind of companies adopt cloud computing?
Finally, a link to an interesting study by the Aberdeen Group, showing visually what the market drivers for cloud adoption are. One finding: The largest group of cloud users are companies ranging from 50 million to 1 billion US-Dollars revenue. Smaller companies while without the hefty investments into their own data centers. 
 
http://smartdatacollective.com/onlinetech/39384/2011-cloud-it-disaster-recovery-statistics

 

Links:
http://www.datacenterknowledge.com/archives/2009/12/30/how-many-servers-can-one-admin-manage/
http://www.gadgetvenue.com/google-servers-04145800/ 
http://news.netcraft.com/archives/category/web-server-survey//
http://royal.pingdom.com/2008/04/11/map-of-all-google-data-center-locations/
http://smartdatacollective.com/onlinetech/39384/2011-cloud-it-disaster-recovery-statistics
http://www.datacenterknowledge.com/archives/2009/10/13/facebook-now-has-30000-servers/