How AWS resources limit and usage are calculated

0
votes

Going through the AWS Service Limits documentation, I can't understand how the AWS resources usage is calculated. Does it decrease every time you launch a new instance? Does it increase when you terminate it? Is it a monthly limit? Annual?

The AWS documentation is unclear.

Update:

In many regions, I have Running On-Demand EC2 instances (max number of EC2s limit is 0).

In other regions I have some instances types limit equal to 0.

In other regions, I have instance type limit > Running On-Demand EC2 instances.

Am I missing something?

2
amazon-web-servicesamazon-ec2documentation
To which particular limit are you referring? That page lists hundreds of limits, each of which could be calculated differently. - John Rotenstein
EC2, to be more precise. - another geek

2 Answers

1
votes

The limit is anytime limit, not monthly or annual. Suppose your limit is 20 EC2 instances, at any time you can have a max of 20 instances (running + stopped).

When you launch a new instance, your instance count (running + stopped) is checked and only if it is less than 20 (your limit) AWS will continue to launch a new instance. Otherwise you will get a message to increase the limit and no instance is launched.

So your limit is checked when you launch a new instance.

(Current running + stopped) + 1 >  instance_limit  ==> Cannot launch
(Current running + stopped) + 1 <= instance_limit  ==> Launched

This limit is per region and per instance type.

0
votes

The Amazon EC2 Management Console has a Amazon EC2 Service Limits Report section that displays the current limits on EC2 resources.

The Running On-Demand EC2 instances limit is described as:

The total number of running On-Demand instances that you can have in this region. Some instance types have different limits for this region that count against your total limit; these are listed below. Check the Current Limit column to find out how many instances per instance type you can run.

The limits can be increased by clicking the Request limit increase link and providing a use-case. AWS Customer Service then evaluates the case and adjusts the limits accordingly.

In some situations, customers request a decrease of their limit to avoid accidentally using some of the more-expensive instance types, or to prevent instances from running in unwanted Regions.