CBT Impact on Snapshot Retention
If CBT is available, Veeam Backup for AWS does not remove the cloud-native snapshot used as a source for image-level backup from the snapshot chain until the next image-level backup session completes. Therefore, at some point in time you may discover that Veeam Backup for AWS ignores retention policy settings and keeps an additional restore point in the snapshot chain.
Consider the following example. You want a backup policy to create image-level backups and to run daily according to the following schedule:
- Image-level backup creation is enabled.
- Backup policy is scheduled to run daily:
- Cloud-native snapshots must be created at 7:00 AM, 9:00 AM, 11:00 AM 1:00 PM, 3:00 PM, and 5:00 PM.
Retention policy for cloud-native snapshots is set to 2 restore points.
- Image-level backups must be created at 7:00 AM and 5:00 PM.
Retention policy for image-level backups is set to 7 days.
Veeam Backup for AWS runs the backup policy in the following way:
- At 7:00 AM, the first backup session will create a cloud-native snapshot, and then will use this snapshot to create a full image-level backup.
- From 9:00 AM to 3:00 PM, subsequent sessions will create only cloud-native snapshots.
- After the backup session runs at 11:00 AM, the length of a snapshot chain (3 restore points) will exceed the retention limit (2 restore points). The earliest snapshot, however, will not be removed as it will be used to track changed data at 5:00 PM when the next image-level backup creation is scheduled.
- After the backup session runs at 1:00 PM and 3:00 PM, Veeam Backup for AWS will remove snapshots created at 9:00 AM and 11:00 AM. The length of the snapshot chain will remain 3 restore points.
- At 5:00 PM, the backup session will create a new cloud-native snapshot. Veeam Backup for AWS will compare this snapshot with the one created at 7:00 AM to identify changed data blocks. After that, the backup session will create an incremental image-level backup based on the data obtained during the snapshot comparison.
- After the snapshot comparison, Veeam Backup for AWS will apply the retention policy and remove the snapshot created at 7:00 AM (as it is no longer needed) and the snapshot created at 1:00 PM from the chain.