Every time people tell you a RAID is no backup. Why?
Every RAID - as long as it's not a RAID0 - guarantees you can access the data even when one or dependent on the RAID type two disks fail.
But if you delete by accident some data on a RAID the data is gone forever. The only way to recover form the accidential deletion of the data is to restore a backup. If there is a hardware issue, a virus, some malware the data also will be gone. That's why it's highly recommended to create a regular backup of your data even you use a RAID to protect your data against a disk failure.
References
5 Simple Reasons Why RAID Is Not a Backup