Issue
I have a script that I run 24/7 that uses 90-100% CPU constantly. I am running this script in multiple virtual machines from Google Cloud Platform. I run one script per VM.
I am trying to reduce cost by using AWS EC2. I looked at the price per hour of t3-micro (2 vCPU) instances and it says the cost is around $0.01/h, which is cheaper than the GCP's equivalent instance with 2 vCPU.
Now, I tried to run the script in one t3-micro instance, just to have a real estimate of how much each t3-instance running my script will cost. I was expecting the monthly cost per instance to be ~$7.20 (720h/month * $0.01/h). The thing is that I have been running the script for 2-3 days, and the cost reports already show a cost of more than $4.
I am trying to understand why the cost is so far from my estimate (and from AWS monthly calculator's estimate). All these extra cost seem to be from "EC2 Other" and "CPU Credit", but I don't understand these costs.
I suspect these come from my 24-7 full CPU usage, but could someone explain what are these costs and if there is a way to reduce them?
Solution
The EC2 instance allows a certain baseline CPU usage: 10% for a t3.micro. When the instance is operating below that threshold it accumulates vCPU credits: which are applied to usage above the threshold. A t3.micro can accumulate up to 12 credits an hour (with one credit being equal to 100% CPU ulitilisation for 1 minute). If you are regularly using more CPU credits than the instance allows will be charged at a higher rate: which I understand to be 5c per vCPU hour.
It may be that t3.micro is not your best choice for that type of workload and you may need to select a different instance type or a bigger instance.
Answered By - Drew Johnston Answer Checked By - Robin (WPSolving Admin)