Raid is not a backup :( For the really important data (photos, documents, ecc) a small 1GB raspberry pi + USB external HDD works great as a Borg server for daily backup, there is no need for a full NAS when you can store all important data in less the a handful of terabytes

A raid is one layer and one copy in a backup.

Inherently to inner copy it provides some redundancy.

Backups need more than one copy.

RAID is not a backup because anything happening within that file system happens to both drives immediately.

ZFS snapshots can help, but this is one layer of a comprehensive backup strategy.

both drives? Only 2 mirrored drives isn't really what a RAID can be.

Constructing a RAID5 with 4 drives provides failover and recovery if one of the drives dies.

You can have as much redundancy as you like on your RAID, but if you fat finger an rm -r it's all gone.

A real backup protects both against hardware faults and accidental deletion.

I’m not implying Raid 5 on its own is a complete backup.

Within a storage array though it does provide redundancy at that level, and generally speaking most people don’t access a raid or NAS at a shell level only where they drop rm -fr’s

Separate and offsite backups are non negotiable, however running a raid 5 locally can greatly reduce storage rebuild/restore time, if a single drive fails the rest of the raid continues to work fine until replaced.

I use RAID1 so that each disk can be pulled and used as standalone.

A RAID 5 setup is more exposed to that. He had to damage all of his disks to lose all data, you need to damage two of your disks to lose all data