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?
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Given the choice between RAID but no backup, and backup but no RAID, it’s backup but no RAID by a mile.
RAID is not backup. RAID is used for increased capacity, throughput or uptime. (Depending on configuration)
Multiple volumes would likely get corrupted just as much with faulty RAM as RAID would. Besides RAM there’s controller, CPU, power supply and possibly more single points of failure in that NAS, that would destroy both RAID and multiple volumes.
So assuming you have external backup, I’d go with RAID for better uptime as opposed to some custom multi volume pseudo-RAID for the same.
You should get/use one external drive for backups that you store separately (can be your 2nd or a new one). Having two separate internal drives for backup is not safe, as the system can damage data on both at the same time (e.g. malware/encryption, data corruption etc.).
RAID is for availability/uptime. I like to compare it to a shop system at the checkout. You can’t have shop payments halted if one drive fails, so you have a RAID. It allows you to repair/replace while the system keeps running and your business keeps operating. In a large business, every hour of downtime can cost you hundreds of thousand of currency, so RAID gets even more sophisticated. Downtime is not an option.
At home this is up to you. RAID can save you some hassle and grant performance, but likely costs you more money than it saves you. Backup is key, so have at least one separately stored copy and depending on the importance of your data, also have an off-site backup.
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.)
The only real advantage of RAID1 is that in some cases you get 2x the read performance. But doing snapshots where you get backups that include changes is more powerful than RAID or a volume copy.
another advantage is not needing to restore from backup when one drive fails. RAID5 oder 6 would be better but does need more than two drives, so with only two RAID1, snapshots and backup of those snapshots is best (0.02€)
