EC2 Computing Unit
lastmod 2021-10-01created 2021-10-011 edits
EC2 Computing Unit. A concept found in the T-series instances of AWS EC2. Provides a relative measure of the integer processing power of an Amazon EC2 instance.
Relationship between ECU and vCPU
When you first create an AWS account and create a virtual server, you choose the server's specs. What gets confusing at this point is the CPU. The terms ECU and vCPU come up, so let's look at how they actually differ.
First, the AWS documentation says:
"One ECU (EC2 Compute Unit) provides the equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor." In other words, it is the performance of a CPU from 8 years ago.
That is, it represents a quantified figure of EC2 computing performance. Then why does AWS display a quantified figure called ECU?
It is because the performance of physical CPUs keeps being upgraded.
Let's look at the following table.
| - | m4.large | m4.xlarge | c4.large |
| vCPU | 2 | 4 | 2 |
| ECU | 6.5 | 13 | 8 |
| Processor | E5-2676 v3 (2.4GHz) 10core | E5-2676 v3 (2.4GHz) 10core | E5-2666 v3 (2.9GHz Bursting 3.5GHz) 10core |
Let's compare m4.large and c4.large.
m4.large can process 3.25 Units per vCPU, m4.xalrge 3.5 Units per vCPU, and c4.large 4 Units per vCPU. If a service generates a large CPU job at once, m4.xlarge has more vCPUs, but c4.large may be more advantageous.
Therefore, computing performance is made into a unit called ECU, and the number of ECUs is used to balance instances against each other.
What is an "EC2 Compute Unit (ECU)" and why was it introduced?
Transitioning to a utility computing model fundamentally changes how developers have been trained to think about CPU resources. Instead of purchasing or leasing a particular processor to use for several months or years, you are renting capacity by the hour. Because Amazon EC2 is built on commodity hardware, over time there may be several different types of physical hardware underlying EC2 instances. Our goal is to provide a consistent amount of CPU capacity no matter what the actual underlying hardware.
Amazon EC2 uses a variety of measures to provide each instance with a consistent and predictable amount of CPU capacity. In order to make it easy for developers to compare CPU capacity between different instance types, we have defined an Amazon EC2 Compute Unit. The amount of CPU that is allocated to a particular instance is expressed in terms of these EC2 Compute Units (ECUs). We use several benchmarks and tests to manage the consistency and predictability of the performance of an EC2 Compute Unit. The EC2 Compute Unit (ECU) provides the relative measure of the integer processing power of an Amazon EC2 instance. Over time, we may add or substitute measures that go into the definition of an EC2 Compute Unit (ECU), if we find metrics that will give you a clearer picture of compute capacity.