MacMost: Backup

Stop Cloning Your Hard Drive As a Backup
Many people still use cloning as a method of backing up a Mac. However, this method is not nearly as useful or robust as a standard Time Machine backup. Files you may think are safely backed up to a clone can actually be completely missing. If you use a clone as a secondary backup, better solutions exist such as online backups, cloud storage, or simply a second Time Machine backup.