A guaranteed backup is useless, it's the guaranteed restore which remains the issue; can anyone provide guaranteed restore? Perhaps not, but we believe that we are pretty close. Backup security requires procedures and testing, and all incidents are logged and tracked against KPIs with automatic escalation based on time and severity.
There is no one size fits all for backup; the service will depend on the systems and coverage required.
For years I was told we a server backup, until some data was deleted, then we found we had nothing; but introduced to Sytec, who recovered the lost files.