[] I would also like to take time that I found the FreeNAS community completely horrible. They're focused solely on people setting up like HIPPA compliant scientific data, or something. It's ZFS for everything. Backups to USB drives are stupid, and you're stupid for having that as a backup strategy, and instead should drop another $1000 on a second NAS for your house, and then backup across a network.

OpenMediaVault's community on the other hand is much more helpful and open to both professional and personal use cases.

A fact that complicates this argument is the prevalence of compressed data formats. A wrong bit in a photo could corrupt the metadata, or a block of DCT coefficients, such that a whole image block or scan line does not decode, effectively ruining the photo. A wrong bit in a .tar.gz could well corrupt the entire archive. You never know where that bad bit will land.

(Yes, this has happened to me -- a single bit flip, probably from RAM error, corrupted a large .tar.gz -- I tracked it down to the bit that changed because I had another copy.)

In fairness to the FreeNAS community, USB drives often aren't a good backup solution:

-> USB thumb drives break all the time. They're terrible choice for any long term storage plan. So you're better off with a HDD / SSD

-> Keeping a USB device inserted all the time means the backup is permanently accessible. This is great for convenience but terrible for a backup as malware (eg ransomware) could access and write to your backup. And even if your backup isn't mounted, it could still be subject to any other physical disaster that knocks out your main archive of data (eg flooding). Backups should always be kept separate - ideally offsite.

-> So now you've got a removable HDD that you need to connect and disconnect frequently. You better buy something reasonably rugged because cheaper drives might fail due to frequent manhandling. Which means you're no longer looking at a budget device.

-> Finally, USB backup solutions cannot be automated. So there's always the risk that someone would let their backups grow out of date. If not out of forgetfulness then just out of plain laziness (eg "I'm too busy to do a backup right now, I'll do it 'tomorrow'").

So while USB storage can be workable as a backup solution, there are a lot of caveats that would invalidate the whole point of a backup if one isn't careful.

I mean if you have an 8TB NAS, and you want to use an 8TB USB drive to backup said NAS locally, I'm not sure I see that as a problem. Backup doesn't HAVE to be significantly more durable than the source material, which is why multiple backups and at least one off site are recommended.

After my time doing support for iomega (so long ago), I don't consider anything really backed up unless there are at least 3 copies, and at least 1 of them is offsite.

The mid to high end stuff are. The lower end is less so. But you pay a premium for decent storage capacity on a decent thumb drive, so either way, you're back to an external HDD / SSD drive.

> "and other USB storage effectively an HDD in an enclosure with a USB interface?"

Indeed. Hense why I said "So you're better off with a HDD / SSD" when referring to other USB storage devices.

> "I mean if you have an 8TB NAS, and you want to use an 8TB USB drive to backup said NAS locally, I'm not sure I see that as a problem. Backup doesn't HAVE to be significantly more durable than the source material, which is why multiple backups and at least one off site are recommended."

I don't have an issue with USB storage per se, I was just saying there are caveats to consider. And while you're right that backups don't have to be more durable than the source, you have to bare in mind that the kind of people who would be looking for advice about using USB devices as a backup solution would likely be the same kind of people who wouldn't have multiple USB devices nor the kind of people who would test their backups to ensure the medium hasn't degraded. They also wouldn't likely be the same people to keep their backups offsite. As these kinds of checks and additions can add significant costs.

Or to put it another way, if one is unwilling to spend $1000 on a second NAS then they are unlikely to want to spend $1000 on a few decent external drives. So that person is going to start scaling back their requirements (cheaper drives, fewer drives, etc) and quickly end up in a situation where their backup solution is total garbage.

Bare in mind, the kind of people who would wander onto FreeNAS's forums looking for backup advice are unlikely to be people like you and I who understand how to implement these things correctly. So it doesn't surprise me that many members of the FreeNAS community veto recommending USB drives knowing how easy it would be for someone inexperienced to get things wrong (eg leaving their USB device connected forgetting that some malware would just write to USB device as well)

I don't follow the reasoning here? It's not like ZFS gets worse if you're not using ECC RAM. Rather it's: ZFS is reliable enough that using ECC RAM becomes worthwhile. ZFS is still more reliable than ext4 even if you're not using ECC RAM.

E.g. with rsync, you use the --backup and --suffix flags.

But if the problem is the RAM or CPU, the bit could also flip before checksumming. Then the incorrectly written data will have a matching checksum and the corruption can't be detected.

That's why ECC is important.