What Counts as Storage Usage"

Question

I received an email with the following information:

Your AWS account XXXXXXXXXXX has exceeded 85% of the usage limit for one or more 
AWS Free Tier-eligible services for the month of December.

Product    	   AWS Free Tier 	            Usage Limit	   AWS Free Tier Usage Limit
                           Usage as of 
                           12/09/2022

AmazonEC2	    27.59677446 GB-Mo     30 GB-Mo              30 GB of Amazon Elastic Block 
                                                                                                     Storage in any combination of 
                                                                                                     General Purpose (SSD) or Magnetic

MY question is, does this 30 GB "Usage Limit" apply to the EBS volume (or volumes) attached
to a single EC2 instance, or does it apply to the EBS volumes attached to all EC2 instances that I 
have in existence?

Also, does/can disk usage increase even when an EC2 instance is stopped?

On no single EC2 instance do I even come close to consuming 85% of the storage capacity
on a single EBS volume, or multiple EBS volumes attached to a single EC2 instance.

Accepted Answer

Looking at [our website](https://aws.amazon.com/free/) the wording for the EBS free tier (which you also have in your question) is "any combination of General Purpose (SSD) or Magnetic". This means you could have a single 30 GB volume; or fifteen 2 GB volumes - completely up to you.

Note that this is the volume size - not how much disk space the operating system of the instance has allocated within the volume. If you have a 30 GB volume and are only using 10 GB of it; that is a 30 GB volume to EBS, not a 10 GB usage. EBS doesn't track the usage of each block; only the total amount of blocks allocated to the volume.

It doesn't matter whether the EC2 instance is stopped or not - it's the EBS volume size that is counted. Note that an operating system might delete some temporary files; or write additional logs to disk as it is shutting down - but that is changing the number of blocks allocated (or free) within the volume. It doesn't change the volume size as EBS sees it.

What Counts as Storage Usage"

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