I have some bad and good news for you.
First might I ask how you connect to the NFS? NFS is a notoriously insecure protocol due to it's origins at the time where the early Internet was without bad guys (or the bad guys were only students/teenies with to much free time or people employed by a secret service so not a big deal in the end) compared to todays golden age of organizied ransomware crimegangs. If you need to use it with your OVH at least use VPN and Kerberos authentification. It's also not really designed to be used outside of a local network.
Second NFS (or any network storage for all that matters) is not supported as a datastore in PBS. One reason is the problem with relieability you encountered but the main reason is the way PBS datastores are organizied: The backup data gets split in a lot of small files (chunks) which are referenced in the backups. The benefit is the high deduplication of PBS but it means that during the backup/restore/verify/sync/prune/garbage collection jobs they need to be read which will lead to quite bad performance.
For reference see these benchmarks:
https://forum.proxmox.com/threads/datastore-performance-tester-for-pbs.148694/
Although there was some discussion on the validity of the benchmark approach it's good enough to show that network storage (especially NFS) isn't really suited for PBS.
Now after the bad news comes the good news:
First although NFS isn't supported and is insecure by design it might still be ok if you only use it in your own (hopefully trustworthy) home network, if your home network gets compromised you will need to rebuild everything from scratch and restoring backups afterwards anyhow.
Second NFS datastore performance isn't great but several people in this forum reported aceptable performance with such a setup. So for a homelab this might be allright. In a business (even a small business) I would setup a dedicated PBS with local storage (two ssds put together in a ZFS or raid mirror) , tightly secured against the rest of the network with it's own custom accounts .
Third: In the end PBS is just (like PVE) software running on a customized debian installation. So you can add the PBS repos to any debian install and use it as backup host:
https://pbs.proxmox.com/docs/installation.html#install-proxmox-backup-server-on-debian
Since it's possible to setup PBS to sync between two backup servers you could utilize this to install PBS on your OVH server and afterwards sync your PBS backup from your local PBS to the OVH server. I do something similiar but with a netcup vserver: My local Proxmox VE hosts, the local PBS and the vserver PBS are connected through a vpn and can't be reached without it. A daily syncjob on the vserver PBS pulls the new backup data from the local PBS for my backup.
They have following permissions for ransomware protection:
- Proxmox VE hosts can backups vms on the local PBS and restore VMs from the local and the netcup PBS but can't modifie or remove them
- The local PBS can movify and remove his own backup data and pull backups from the remote PBS but can't modify/ remove the backups on the remote PBS
- The remote PBS can pull backups from the local PBS and modify/remove his own backup data but can't modify/remove the backups on the local PBS.
I hope everything is clear, ask if you have any questions.
