Health Check for Backup Files

You can instruct Veeam Agent for Microsoft Windows to periodically perform a health check for the latest restore point in the backup chain. During the health check, Veeam Agent performs a CRC check for metadata and a hash check for data blocks in the backup file to verify their integrity. The health check helps make sure that the restore point is consistent, and you will be able to restore data from this restore point.

To run the health check periodically, you must enable the Perform backup files health check option in the backup job settings and define the health check schedule. By default, the health check is performed on the last Friday of every month. You can change the schedule and run the health check weekly or monthly on specific days.

Limitations for Health Check

• The health check is not performed during an active full backup job session started manually or automatically by schedule.
• The health check is not supported for backup files created in Microsoft OneDrive.
• The health check is not performed during a backup job session that creates a restore point in the backup cache.
• The health check is not performed during the backup cache synchronization process.

How Health Check Works

When Veeam Agent for Microsoft Windows saves a new restore point to the backup location, it calculates CRC values for backup metadata and hash values for data blocks in the backup file, and saves these values in the metadata of the backup file, together with the backed-up data. During the health check session, Veeam Agent uses these values to make sure that a verified restore point is consistent.

Veeam Agent for Microsoft Windows performs the health check in the following way:

1. During the backup job session, Veeam Agent for Microsoft Windows creates a new restore point in the backup chain.
2. At the end of the backup job session, Veeam Agent for Microsoft Windows performs the health check. It calculates CRC values for backup metadata and hash values for data blocks in the backup file and compares them with the CRC and hash values that are already stored in the backup file.

During the health check, Veeam Agent for Microsoft Windows verifies the latest restore point in the backup chain (restore point created with the current backup job session — the session during which the health check is performed). If the latest restore point in the backup chain is incomplete (for example, if the current backup job session completed with an error), Veeam Agent checks the restore point preceding the latest one.

If the health check does not detect data corruption, the backup job session completes in a regular way.

3. If the health check detects corrupted data, Veeam Agent for Microsoft Windows completes the backup job with the Error status and starts the health check retry process. The health check retry starts as a separate backup job session.

Depending on the revealed data corruption, Veeam Agent performs the following actions:

• If the health check has detected corrupted backup metadata in the full backup file, Veeam Agent marks the backup chain starting from this full restore point as corrupted in the Veeam Agent for Microsoft Windows database. During the health check retry, Veeam Agent transports the entire data selected for backup from the Veeam Agent Computer, creates a new full backup file in the target location and saves transported data blocks to this backup file.
• If the health check has detected corrupted backup metadata in the incremental backup file, Veeam Agent removes information about this incremental restore point and subsequent incremental restore points from the Veeam Agent for Microsoft Windows database. During the health check retry, Veeam Agent transports incremental data relatively the latest valid restore point in the backup chain from the Veeam Agent computer, creates a new incremental backup file in the target location and saves transported data blocks to this backup file.
• If the health check has detected corrupted data blocks in the full or incremental backup file, Veeam Agent marks the restore point that includes the corrupted data blocks and subsequent incremental restore points as corrupted in the Veeam Agent for Microsoft Windows database. During the health check retry, Veeam Agent transports data blocks from the Veeam Agent computer. In addition, Veeam Agent transports data blocks that have changed since the backup job session that has triggered the health check. Veeam Agent stores these data blocks to the latest restore point that has been created with the current backup job session (session that has triggered the health check retry).

Health Check Retries

The health check itself is started during the backup job session or the job retry session if the backup job session has failed. If the attempts are not successful, Veeam Agent for Microsoft Windows will perform the health check during the last job retry in any case.

If the health check detects corrupted data, Veeam Agent for Microsoft Windows completes the backup job with the Error status and starts the health check retry process. The health check retry starts as a separate backup job session. During the health check retry, Veeam Agent attempts to transport data blocks for the corrupted restore point from the Veeam Agent computer to the target location.

For a backup job started automatically upon schedule, the number of health check retries is equal to the number of job retries specified in the job settings. For a job started manually, Veeam Agent for Microsoft Windows performs 1 health check retry.

Related Topics

Configuring Backup Job