RAID will only protect you (and your data) from a disk failure. If your systems support hot-plug disks, or you have some hot-spares in your system, you might even recover from the failure without any downtime. But all this will not protect you from a data corruption. That's what backups are for.
Today i had an unexpected power outage which caused some files to become corrupt on one of my VMs. To make the matters worse, the files in question were MySQL data files. Not just any files, the undo logs. If there is a server crash (and there was) and the undo logs are not consistent (and they weren't), the database doesn't start. Recovery procedures might get you to a running database in read-only mode, if you are lucky and no other data files are corrupted. In read-only mode, you have a chance to export the uncorrupted data and try to restore it on a fresh database. But, when you have backups, you don't have to rely on luck. Just reinstall the software, do the basic initial configuration (if needed) and restore from the last night's backup. No luck needed.