It appears that vzdump backup uses cephfs files for backup images. By default, cephfs has a maximum file size of about 1TB, which suggests that vzdump will fail if it is run to back up a guest with more than 1TB of storage in use.
What does vzdump do in this case? If it fails, does it give an error message which suggests what the problem is so it can be resolved?
What does vzdump do in this case? If it fails, does it give an error message which suggests what the problem is so it can be resolved?