Understand how the usage of the cloud backup repository is affected for Veeam Cloud Connect Backup (VCC-B)
TABLE OF CONTENTS
Description
Please review this article to understand how the usage of the cloud backup repository is affected, how the retention policy works and why the usage of the cloud backup repository may fluctuate.
Important Notes
The reverse incremental backup method is not mentioned here as this method is not recommended for backup jobs with cloud repositories for the backup destination.
Definitions
Incremental Backup
When an incremental backup job runs (also referenced as Forward Incremental Backup in Veeam documentation), it means that increments (changes since the last backup) are saved into new files dependent on previous files in the backup chain on your backup storage.
Synthetic Full Backup
When a synthetic full backup job runs, Veeam Backup & Replication consolidates backup data from the previous full backup file and the chain of subsequent incremental backup files on your backup storage and writes consolidated data into a new full backup file. Performing synthetic full backup jobs reset the backup chain. Any new subsequent incremental backup files use the latest synthetic full backup file as the new starting point.
For more details on Incremental Backup or Synthetic Full Backup, please see the articles in the References section below.
Retention Policy details
If the backup job is configured to use the forward incremental backup mode with periodic synthetic full backups, Veeam Backup & Replication will keep more restore points in your cloud backup repository than the number of restore points configured on backup jobs. This is absolutely normal to ensure a recovery according to the retention policy.
Without the full backup, a backup chain of forward incremental files would be completely useless. So, a previously used full backup file will be kept in your backup storage until it is automatically deleted according to the retention policy configured on backup jobs.
Example below with a backup job and a retention of ten (10) restore points in a daily schedule:
For the first ten (10) days, ten (10) recovery points exist in the backup storage.
Now, what happens on the eleventh (11th) day ?
Will the first (1st) backup be deleted to keep the last ten (10) days ?
The answer is No. As previously mentioned, all incremental backups in the chain depend on the full backup. The whole backup chain cannot be deleted for now. To ensure to keep ten (10) recovery points available for recovery, a new whole backup chain must be created.
Once ten (10) recovery points are secured, the previous whole backup chain will be deleted.
Throughout the days, the number of recovery points and your cloud backup repository usage will continuously fluctuate.
Using a different backup method will change the number of recovery points and the usage behavior of the cloud backup repository.
References
https://helpcenter.veeam.com/docs/backup/vsphere/synthetic_full_backup.html?ver=120
https://helpcenter.veeam.com/docs/backup/vsphere/synthetic_full_hiw.html?ver=120
https://helpcenter.veeam.com/docs/backup/vsphere/retention_incremental.html?ver=120
https://helpcenter.veeam.com/docs/backup/hyperv/backup_methods.html?ver=120