- Synology NAS is accessible on LAN & phones sync photos when at home
- Nightly rsync from internal NAS storage to 1 external (non-raid) hard drive
The nightly rsync does not delete files, so the external hard drive is pretty close to an off-site backup even though it's still attached. The only better thing I've thought of doing is mounting it ro after backups + re-mounting before backups.
At the end of the day we get 3 copies of data: the photo on your phone, the photo on the shared NAS, and the photo on an external hard drive that spends 99% of its life spun down.
IMO the biggest remaining risk to this is a house fire at night while you are at home. You wake up to alarms and smoke and run out the door without your phone. All three copies of your photos will burn at once. This is where an additional off-site would be valuable. That might be a second external hard drive that you store off-site and re-sync every few months, or maybe an encrypted cloud backup using restic.
Still it sucks and it shouldn’t happen, hopefully it’s just a reporting error in the app.