What does ECU units, CPU core and memory mean when I launch a instance

Question

When I launch an instance on EC2, it gives me option for t1.micro, m1.small, m1.large etc. There is a comparision chart of vCPU, ECU, CPU cores, Memory, Instance store. Is this

Answer 1

ECUs (EC2 Computer Units) are a rough measure of processor performance that was introduced by Amazon to let you compare their EC2 instances ("servers").

CPU performance is of course a multi-dimensional measure, so putting a single number on it (like "5 ECU") can only be a rough approximation. If you want to know more exactly how well a processor performs for a task you have in mind, you should choose a benchmark that is similar to your task.

In early 2014, there was a nice benchmarking site comparing cloud hosting offers by tens of different benchmarks, over at CloudHarmony benchmarks. However, this seems gone now (and archive.org can't help as it was a web application). Only an introductory blog post is still available.

Also useful: ec2instances.info, which at least aggregates the ECU information of different EC2 instances for comparison. (Add column "Compute Units (ECU)" to make it work.)