I have a DS220+ with 2 identical drives, configured as RAID, so just one volume. Everything was working great, but to access the new object-recognition in photos, I added RAM, which caused some corruption and now the volume is read-only and won’t repair itself (even after removing the RAM). So now I’m preparing to do an external backup and rebuild the NAS. But now I’m wondering: If volume issues are more likely than drive issues, should I forget about RAID, create one volume on each drive, and use the second volume as a local backup? Or is RAID still the best first line of defence? (Or is there a way I can do both with two drives?
Was it RAID 0 (striped), or RAID 1 (mirrored)?
In general, a mirrored RAID is best for minimizing data loss and downtime due to drive failure, while separate volumes and periodic backups is best for recovering from accidental file deletion or malware. (I.e., if a RAID gets told to write bad data, it’ll overwrite the good data on both drives at once.)
If you want the best of both worlds with just two drives, try zfs—you can mirror the drives to protect against drive failure, and make snapshots to protect against accidental data loss. (This still won’t protect against everything—for that you should have some kind of off-site backup as well.)