Archive Backup Chain
If you enable backup archiving for a backup policy, Veeam Backup for Microsoft Azure will create a new backup file in an archive repository during every archive session. A sequence of backup files created during a set of archive sessions makes up an archive backup chain.
The archive backup chain includes backup files of the following types:
- Full — a full archive backup file stores a copy of the full Azure VM or Azure SQL database image.
- Incremental — incremental archive backup files store incremental changes of the Azure VM or Azure SQL database image.
To create an archive backup chain for an Azure VM or Azure SQL database protected by a backup policy, Veeam Backup for Microsoft Azure implements the forever forward incremental backup method:
- During the first archive session, Veeam Backup for Microsoft Azure detects backed-up data that is stored in the full backup file and all incremental backup files existing in the standard backup chain, creates a full archive backup file with all the data, and copies this file to the archive repository. The full archive backup file becomes a starting point in the archive chain.
- During subsequent archive sessions, Veeam Backup for Microsoft Azure checks the standard backup chain to detect data blocks that have changed since the previous archive session, creates incremental archive backup files with only those changed blocks, and copies these files to the archive repository. The content of each incremental archive backup file depends on the content of the full archive backup file and the preceding incremental archive backup files in the archive backup chain.
Full and incremental archive backup files act as restore points for backed-up Azure VMs or Azure SQL databases that let you roll back instance data to the necessary state. To recover an Azure VM or an Azure SQL database to a specific point in time, the chain of backup files created for the instance must contain a full archive backup file and a set of incremental archive backup files.
If some file in the archive backup chain is missing, you will not be able to roll back to the necessary state. For this reason, you must not delete individual backup files from the archive repository manually. Instead, you must specify retention policy settings that will let you maintain the necessary number of backup files in the archive repository. For more information, see Retention Policy for Archived Backups.