RAID systems can be configured for use as a backup drive. Software running on a computer or server manages the backups, and files are copied to a RAID which is directly attached or connected to a network as a NAS device.
Because RAID systems have more than one drive and use redundancy, there is a common belief that data is protected and doesn't require a secondary backup. But, while redundancy provides some safety against data loss, there is no protection if more than one drive fails.