RAID iS nOt bAcKuP 🤡
Yes, RAID 1 is. What you wanted to say is “RAID is not an off-site backup”.

We have our offsite backup NAS mounted as a read/write device with no versioning.

We're doing backup "right".

The point behind the claim is that failures tend to cascade. So a RAID setup, even RAID 1 setup offer less protection than a secondary raid, or a separate disk you connect and disconnect just for backups, or the best solution: offsite, as you mentioned.

That's why we often say that RAID provides redundancy, but is not a backup. For example if your RAID driver fails or burns might kill both drives... Or if your bedroom caught fire, you might lose the entire raid and all drives, but not the disk you keep in your livingroom... Etc...

So there's a method to the madness

a backup of WHAT? data? no. Hardware/disk? yes.

If you corrupt your data by a ransomware on one of them, it will be automatically corrupt on the other one(s).

It is NOT a backup of your data. But it's a backup of your storage device.

@netikras Good point

Kangaroos are running wild

https://youtube.com/watch/...

@12bitfloat yeah.. I've also seen enough raid 1s and 5s and 10s fail as soon as the faulty disk is removed -- the remaining good one/spare sometimes dies that exact moment. Other times - when replication starts into the spare.

Naah. Data is not safe enough on RAIDs to deserve to be called a backup

no, it is NOT a backup.

proof by trivially basic logic:

delete a file on a raid-ed volume. it's gone from ALL drives.

it's redundancy against one specific point of hardware failure. and not any kind of backup.

@tosensei by this logic, delete all your files on your backup drive. Boom, they’re gone. Backup is not a backup

@kiki the flaw in your argumentation: you confuse "deleting stuff on the main storage" with "deleting stuff on the backup".

also: when you delete stuff on your backup drive, it does NOT get deleted on the main drive in the progress.

@tosensei but if I delete something from one drive in raid 1 array it doesn't get deleted from the other drive either

@kiki well - it does if your raid setup is actually working, and not completely shite.

because, you know - that's what raid 1 does. mirror everything happening to any drive to all other drives.

...are you _trying_ to appear dumb right now?

@tosensei but that's exactly my point — raid 1 is working, working as a backup that is

@kiki no. it is mirroring. not backing up.

it does not protect you against data loss by accidental deletion, because the deletion gets immediatelly propagated to all drives...

@tosensei it doesn't! If I delete data manually from one drive by connecting it alone, and not from the virtual drive that abstracts both real drives, raid will put the data back

@kiki if you delete data from one drive in a two-drive raid 1, you'll have a broken raid volume, because the controller has no way of figuring out which data is the valid one.

also, if you delete data from one drive manually, you're breaking the system on purpose. which only an idiot like ostream would do.

again: are you trying to appear dumb? seriously asking.

@tosensei alright, you got me. Perhaps I went too far and too obvious with "backup is not a backup".

@kiki there is no joke obvious enough that there isn't a group of idiots stating it as serious belief.

@tosensei isn't that Poe's "parody of extremism is indistinguishable from extremism"?