Eight months later, Netcraft reported in May, it had grown by more than 33%, to 158,000 servers.
The Netcraft survey is limited in how much it can see and must estimate the number of computers that operate behind the "Web-facing" servers of a given company. It says on its website that its counts miss those servers that don't respond directly to an HTTP call, such as the database servers, firewalls, proxy servers, load balancing servers and others that lie behind the ones it sees at a given address. It estimates that it counts about two-thirds of the servers in use at a large hosting service, such as Amazon.
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But the Netcraft counts do provide a relative measure of growth. Whatever Amazon's total server count, it increased by more than a third in a recent eight-month period. In 2009, Netcraft counted 4,600 servers at Amazon.com. Four years later, it saw a 30-fold increase to the 158,000 figure.
How much of that increase can be attributed to retail, versus growth in AWS cloud services, can't be distinguished. Last year, the AWS unit represented (at most) 5% of Amazon.com's revenue.
Whatever the number of servers used by AWS, that number is probably dwarfed by Facebook, Google and one or two other Internet giants. Microsoft, for example, when it built a giant 700,000 square foot Azure data center outside Chicago, reported it had the capacity for 300,000 servers. It's never said how many servers have actually been installed. Microsoft, Google, Apple, Amazon.com and other companies all regard their total server count as a proprietary, closely held secret.
Facebook has filled its twin 330,000-square-foot "data halls" at its Prineville, Ore., complex. Each contains "tens of thousands of servers," according to the company. Together, they are roughly equal in square footage to Microsoft's Chicago center, but Prineville's design includes large air passageways with its passive cooling system design. A server at Prineville probably occupies a slightly larger average footprint in terms of overall building space than one in a data center with air conditioners. If the Prineville buildings are fully equipped, they still probably don't reach Microsoft's 300,000 count.
For the record, Netcraft counted 19,100 Web-facing servers at the Azure cloud's address in its July report, but Microsoft executives have previously said its Chicago data center hosts Bing search, Sharepoint application collaboration services, Office 365, Microsoft Dynamics CRM software-as-a-service, and other services that don't necessarily show up with an Azure address. The total server count is probably much higher.
Perhaps a better measure of comparison is the number of websites being hosted by the cloud servers. For Azure, Netcraft found 170,000 websites hosted on those 19,100 servers in its July count. For Amazon.com, it found 11.6 million hosted on the 158,000 servers in May. That may be a clearer measures of the lead AWS has established among cloud providers.