EBS Snapshot – An EBS snapshot is a backup of a single or individual EBS volume. The EBS snapshot contains all the data stored on the EBS volume at the time the EBS snapshot was created .
AMI – Amazon Machine Image . By the abbreviation itself we can identify its for an EC2 instance. An AMI image is a backup of an entire EC2 instance. Associated with an AMI image are EBS snapshots. Those EBS snapshots are the backups of the individual EBS volumes attached to the EC2 instance at the time the AMI image was create . Simply we can say collection of snapshot are AMI.
As a Backup Strategy, Should You Create AMI Images or EBS Snapshots?
The answer to this depends on many factors, including your restore time objective, desired restore procedure, and many other business-related factors .
AMI:
Due to some reason if your instance failed or having some issue , and if you like to restore quickly then using AMI is best option . Reason behind this when you have multiple individual EBS volumes attached to that instance you no need to manually restore individual snapshot . When you launch using AMI it will restore all your snapshot to that instance automatically.But keep in mind while crating AMI you should have selected the disk for including in that AMI.
it’s not only to restore the existing AMI . If you want spin up new EC2 instance from that image AMI is better option.
AMI can be used as Golden Image for your environment , like as base template to launch more EC2 instances , contains harden OS and all your installed software bundles and configuration.
Snapshot:
If your EC2 instance contains a mix of static EBS volumes (for example, a non-changing root volume) and dynamic EBS volumes for example, a data volume keep change, then creating EBS snapshots is better solution.
Since EBS snapshots can be thought of as incremental, you only pay for the storage of the changed data. So creating multiple EBS snapshots of a non-changing EBS volume will not incur high charges.
The process of creating an AMI image will also create EBS snapshots. So even if you need to restore a single EBS volume, you can do so from the individual EBS snapshot .
Conclusion:
You can use EBS snapshot for your EBS volumes regular daily incremental backups . May be you can use with AWS snapshot lifecycle manager or some backup tools like commvault . AMI you can plan for only root disk or whenever you like create standard template OS image from that instance . Also you can consider monthly or some longer scheduled interval AMI backup , for the purpose of faster restoration of critical EC2 instances.