Joe McKendrick over at ZDNet blogs points to CloudScaling.com, which has done an analysis of Amazon's EC2 cloud computing service.

Randy Bias says he has figured out the size of EC2 from two reliable sources: 40,000 servers, give or take 5,000 servers.

Combined with Amazon's financial results, he estimates that EC2 produces $220 million in revenues in the most recent fiscal year, and growing at 10 per cent per year.

A lot of Mr Bias's numbers are educated guesses but they are very educated guesses. He used to build and run large 10,000 ft data centers.

Here are some of his figures:

Known For Reasonably Certain

• Amazon does not oversubscribe cores
• Amazon uses Rackable servers, mostly 2U dual-socket systems, with 8 cores, probably theS2108 models
• Some of their older systems are 2U dual-socket systems with 4 cores total
• The AWS target cost for servers is roughly $2-2.5K
• Initial overall target utilization rate for EC2 was 70-75%
• Recently AWS has been having regular capacity issues (due to growth?)
• Amazon is beginning to move some retail site capacity onto EC2
• RAID is used for the disk subsystem, probably in a RAID-0 (striped) configuration.

Mostly Sure

• Most of the servers are likely in the US availability zones vs. the EU zones, maybe 75-80% of total capacity
• Amazon probably runs 8 500GB SATA drives per system
• At 2U, Amazon runs 16-18 servers per rack, probably 16
• Amazon uses the same, or a very similar, physical hardware platform for all instances sizes; it has changed over time and there are a few generations, but they don't buy or 'silo' the hardware if they can help it

Inferred or Assumed

• At 40,000 servers evenly distributed across 6 availability zones we know:
• ___ 6,700 servers per zone
• ___ 417 racks per zone, 2,500 racks total
• ___ 2 * 30A circuits per rack (assuming no redundant PSUs) at a draw of probably 6.5kw
• ___ That's roughly 16.25MW of total power, not including that of the critical systems (HVAC, etc.) or the other AWS services
• ___ 95,000 used sq ft, which probably means 200K total sq footage including support systems
• Taking a good guess, I'd say as many as 20% of instances are 'reserved', meaning purchased at a 70% discount one year in advance
• Another good guess is that up to 20% of EC2 capacity is being reserved for the retail site (Amazon.com

He estimates the total size of the "cloud" market to be as much as $600m and growing at 10 to 20 per cent a year.

Foremski's Take: I think his estimate of the cloud computing market could be on the low side especially the growth numbers. There are a lot of different types of web services being offered and these are cloud computing services. I would expect to see much higher growth numbers since it is coming off of a low base.

Also, the size of Amazon's cloud is likely on the low side since it uses the same architecture to run its business.