From the Syncthing FAQ (https://docs.syncthing.net/users/faq.html#is-syncthing-my-id...):

> Is Syncthing my ideal backup application?

> No. Syncthing is not a great backup application because all changes to your files (modifications, deletions, etc.) will be propagated to all your devices. You can enable versioning, but we encourage you to use other tools to keep your data safe from your (or our) mistakes.

I would argue in conjunction with zfs snapshots (can be every minute), it's safe and the caveat no longer applies.

If you accidentally reformat the ZFS drive, that will delete all your files and snapshots and then Syncthing will replicate those deletions.

I'm really not super familiar with Syncthing, but it sounds like it's niche is availability as opposed to durability.

Even if you format your drive and Syncthing copies over the empty files you will still have a history of snapshots on the other host running ZFS snapshots.

What if you accidentally format the drive on the host with the ZFS snapshots? Won't that result in synchronizing the deletion of those files to all your other devices?

Yes, for his setup (if I understand right). I'm suggesting having two hosts with ZFS snapshots running (independent of each other) with Syncthing between. So if you delete the files on one host and they get Syncthing'd across there will still be a ZFS snapshot history on the other host. I'd also have a cold storage backup on hand that is also ZFS. Having your backup as a regular filesystem is a very nice feature once it comes to recovery.

syncthing has send-only and receive-only folders. You can set a receive-only folder on your backup device and send-only on your phone or whatever. With incremental backups it's not an issue. Syncthing is just the tool to get your data to the place it needs to be. Just like rsync or cp

Anyone taking backups seriously already knows the 3-2-1 rule anyway.

Syncthing frequently stops syncing on my phone and requires me to delete everything and resync. I'm using receive-only folders. I think I'm an exception but it's been a pain in the ass.

If you accidentally delete your data, your data will be deleted.

This is the curse of sharp tools. Don't run unix if you don't want rm to rm.

I still also have backups, and zfs snapshots on a different independent machine.

I'm coming to the same conclusion. I was running Freenas and my file server died and then my files were locked up on that host. Luckily I was using Syncthing to the central file server but I just added new links between individual devices and then it didn't matter that my file server died (except for files that were not on any non-server device). File servers are annoying for disconnected usage. I was using duplicacy for backups but the storage format is annoying (not just regular files) and nothing is more reliable than regular file systems. So now with my new setup I'm using a Rpi4b with NixOS and ZFS data drive over a USB3 dual drive docking station with UASP. I can boot from a USB3 thumb drive (which I do) or an SSD in the docking station and still have another SATA port for the data drive. (The downside of this is RAID doesn't work over USB.)

I'll have two of the same RPi servers in different locations with all software running (like a hot swap) with Syncthing keeping them in sync while ZFS snapshots keeps a history. I can plug in a cold storage drive in the second dock slot once in a while too. I'll have a spare RPi4b on the shelf in case it dies. If my server dies I can take the off site hot backup home and reconfig the network and then it is my primary server. With remote duplicacy backup I'm days away from getting going again. So ZFS snapshots + Syncthing and cold storage is where I'm going (for home use). Also I want to stick with Linux because I set up Freenas 5 years ago and now I forget how to admin it so I'd rather just keep with ZFS and Linux (the zfs send from freenas to zfs recv on Linux works perfectly).