Just How Big is the Amazon EC2 Cloud?

Amazon Web Services, the cloud services arm of Amazon.com, plays its cards close to its chest when it comes to the size of their data centers. But a new probe methodology developed by Accenture Technology Labs Research Manager Huan Liu and his team indicates that the Amazon EC2 compute-as-a-service platform may run on as many as 454,000 servers across 7,100 racks internationally- which would make it the largest cloud service provider on the market by a wide margin.

Liu’s blog entry goes into depth on his methodology, for the curious. But the basic idea is that it’s possible to correlate the IP addresses assigned to an instance with the server rack that it’s running on. Once you figure out the pattern of assigned IP addresses, it’s possible to make an educated guess as to the number of racks. That’s where things get a little technical, but suffice it to say, the team devised a way to use public and private instance IP addresses and DNS listings to get a count. Here’s what Reddit might affectionately term the TL;DR version:

  • Enumerate all public IP addresses EC2 uses
  • Translate a public IP address to its public DNS name (e.g., ec2-50-17-204-150.compute-1.amazonaws.com)
  • Run a DNS query inside EC2 to get its internal IP address (e.g.,
  • Derive the rack’s IP range from the internal IP address (e.g., 10.2.12.x/22).
  • Count how many unique racks we have seen, then multiple it by the number of physical servers in a rack (we assume it is 64 servers/rack).

There’s a couple of caveats to this method: If a server rack isn’t running any EC2 compute instances at all, it won’t show up to this kind of probe.  It’s also assuming that 64 servers/rack figure without knowing for sure. Finally, Amazon EC2 may not be the only service running on those racks – some of that hardware could (and almost certainly does) run other AWS cloud services, including Amazon S3 cloud storage or Amazon SimpleDB databases).

Services Angle

Assuming for a moment that Accenture Technology’s figures are correct, it means that Amazon is very probably leaps and bounds ahead of other cloud service providers in terms of sheer size.  For comparison, Data Center Knowledge just updated its “Who Has the Most Web Servers?” list in March 2012, and Akamai Technologies led the pack with 105,000. Facebook is in seventh place with 60,000 servers.

Amazon.com is primarily an e-retail company, and doesn’t like to make a lot of noise about its cloud service growth – at least, not enterprise cloud services – and leaves a lot to speculation. But again assuming that Amazon does indeed have 454,000 servers, well, we don’t know if it’s making any money, but it’s probably a safe assumption.