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AWS bins elastic compute units, adopts virtual CPUs

Customers tired of wrapping their heads around odd computing power metric

Gartner analyst Kyle Hilgendorf has spotted something very interesting: Amazon Web Services seems to have stopped rating cloud servers based on EC2 compute units (ECUs), its proprietary metric of computing power.

ECUs were an odd metric, as they were based on “... the equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor … equivalent to an early-2006 1.7 GHz Xeon”. AWS rated EC2 instances according to the number of ECUs they employed.

Hilgendorf's blog post links to this AWS page describing EC2 instances ad offering only vCPUs. But a trip into archive.org's record of the page as it appeared on April 13 shows that AWS used to sell both Virtual CPUS (vCPUs) and ECUs.

AWS has confirmed the change has taken place to The Register.

The EC2 FAQ spells it out. Emphases are AWS' own:

Q: Why don’t I see EC2 Compute Units, or ECUs, any more?

Elastic Compute Units have been replaced with processor information and clock speed.

Q: Why did you replace the ECU measurements?

We replaced the ECU measurements in order to provide a more standardized comparison method between instance types. We try to provide measurements that are easy to understand, and more universal.

Hilgendorf writes that the ECU “was always a gnarly concept to grasp".

The Reg understands that AWS customers shared very similar sentiments on a regular basis. Rather than try to educate customers about its odd metric, AWS has simply decided to adopt the far-more-easily-understood and widely-adopted vCPU moniker.

As it transpires, the cloudy colossus foreshadowed it might one day move away from ECUs. In this FAQ it says “Over time, we may add or substitute measures that go into the definition of an EC2 Compute Unit, if we find metrics that will give you a clearer picture of compute capacity.”

vCPUs are clearly that “clearer” description, and as of now they're AWS' standard way for describing the engines in its rent-a-servers.

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