How Health Check Works

When the backup appliance saves a new backup restore point to a backup repository, it calculates CRC values for metadata in the backup chain and saves these values to the chain metadata, together with the instance data. When performing a health check, the backup appliance verifies the availability of data blocks and uses the saved values to ensure that the restore points being verified are consistent.

If you have enabled health checks for the backup policy, the backup appliance performs the following operations at the day scheduled for a health check to run:

1. As soon as a backup policy session completes successfully, the backup appliance starts the health check as a new session. For each restore point in the standard backup chain, the backup appliance calculates CRC values for backup metadata and compares them to the CRC values that were previously saved to the restore point. The backup appliance also checks whether data blocks that are required to rebuild the restore point are available.

If the backup policy session completes with an error, the backup appliance tries to run the backup policy again, taking into account the maximum number of retries specified in the automatic retry settings. After the first successful retry (or after the last one out of the maximum number of retries), the backup appliance starts the health check.

2. If the backup appliance does not detect data inconsistency, the health check session completes successfully. Otherwise, the session completes with an error.

Depending on the detected data inconsistency, the backup appliance performs the following operations:

• If the health check detects corrupted metadata in a full or an incremental restore point, the backup appliance marks the backup chain as corrupted in the appliance configuration database. During the next backup policy session, the backup appliance copies the full instance image, creates a full restore point in the backup repository and starts a new backup chain in the backup repository.

• If the health check detects corrupted disk blocks in a full or an incremental restore point, the backup appliance marks the restore point that includes the corrupted data blocks and all subsequent affected incremental restore points as incomplete in the appliance configuration database. During the next backup policy session, the backup appliance copies not only those data blocks that have changed since the previous backup session but also data blocks that have been corrupted, and saves these data blocks to the latest restore point that has been created during the current session.