- All ephemeral storage will be lost regardless of whether you stop or terminate the instance.
- EBS storage will persist if you stop the instance, and usually will also persist if you terminate it.
To clarify the above point - if the
DeleteOnTermination flag is set, the EBS volume will be deleted when the instance terminates. By default, most root EBS volumes are set to be deleted on termination - you can change this using
ec2-modify-instance-attribute. All EBS volumes you have manually attached to the instance default to having
DeleteOnTermination set to false (i.e. they will persist).
S3 backed (instance store) AMIs cannot be stopped (only terminated). (Which makes sense, since the root disk would be re-provisioned, and the instance restored from the AMI anyway.)
If you do not intend to use this instance for a month, it would be more economical to:
- take a snapshot of the root volume
- terminate the instance
- and delete the EBS volume.
Since snapshots are compressed (and only store actual 'data' - not provisioned space), this will likely cost significantly less - and will allow you to return to the same state (since all the ephemeral data will be lost anyway). If you already have existing snapshots the additional cost will further be reduced, since snapshots are differential. (You can, of course, create an AMI from a snapshot, and launch a new instance using that AMI at any time).
On the other hand, you will be charged for the space provisioned by your EBS volume(s), regardless of the actual amount used, for as long as they exist.