Personally my NAS isn't my main storage. I still use Google Photos and Google Drive for my important stuff, I just need to configure Rclone to download my stuff on it.

The one thing I'm really self hosting only is my music, outside of the couple of CDs and downloading from iTunes, I don't have a proper backup.

I’m currently using just an external drive to backup too, I use cloud storage for all my personal files, but my systems (I run a lot of servers that would be a pain to rebuild and reconfigure) and all my Linux ISOs are backed up nightly to a large external hard drive. However, I appreciate that I’m not covered for the local disaster scenario if my house was to set on fire, so my plan is to also implement Backblaze cloud backups of my server machine so I could have cloud backups of my backups at least.

you're chances of being hit by lightning is probably higher than all 3 copies of your data being inaccessible all at the same time for whatever reason.

Piggyback: anyone using LTO for backup/archival in their homelab?

You didn't say how you currently keep your data...

I'd be more concerned to lose data that is stored in the cloud than on my private network.

The adage "there is no cloud, it's just someone else's computer" is still true.

If you are afraid to lose the data on your clients and servers in your private network, improve your backup strategy and make sure to have one backup off premise (in a safe deposit box if needs be).

It doesn't hurt to improve overall security on your private network, either. 😉

I'd be more concerned to lose data that is stored in the cloud than on my private network.

The adage "there is no cloud, it's just someone else's computer" is still true.

If you are afraid to lose the data on your clients and servers in your private network, improve your backup strategy and make sure to have one backup off premise (in a safe deposit box if needs be).

It doesn't hurt to improve overall security on your private network, either. 😉

Immutability! For some reason nobody here mentioned this! There's only one thing which can protect you against ransomware - backup storage with immutability! It can be S3, custom script setting immutable flag, read-only snapshots and so on...

But... You need to make sure, that your backup storage is properly tightened, so even you, as the owner, cannot change immutable data without physical access to the server.

I store my documents in a 3 disk raid 5, which is backed up to a brand new NAS red, which is backed up to a 8TB external via Borg, and finally to my 1 TB OneDrive via rclone.

So at this point, no...

3-2-1-1-0 and you have 99.9999% covered. I replicate all backups between four physical locations, doesn't get more overkill than this. For personal use I even have a backpack with external HDD in it, that syncs the most important data every day.