NFS backup storage fails silently in Proxmox more often than it should. The backup job looks fine, the task says OK, but the files aren’t there or they’re empty. The GUI just doesn’t show you the real error.
Why the GUI hides the error
Proxmox’s backup log in the web interface only shows the high-level status. When the NFS mount drops or the server rejects the write, the actual error is buried in the system logs. You have to go looking for it.
Check the task log first
Even if the task shows as successful, open the task log and look for warnings. Sometimes there’s a line like WARN: unable to write ... or a timeout that doesn’t fail the whole job. That’s your first clue.
Then check the system logs
The real error is usually in journalctl or /var/log/syslog. Run this on the Proxmox host:
journalctl -u pvescheduler -u vzdump --since "1 hour ago" | grep -i nfsOr look for NFS mount errors:
dmesg | grep -i nfsCommon culprits: stale file handles, permission denied on the export, or the NFS server going read-only. The GUI won’t tell you any of that.
My take
Don’t trust the green checkmark. If you’re backing up to NFS, set up a separate monitoring script that checks the backup files actually exist and have size. Or just run a test restore every so often. It’s annoying, but it’s the only way to catch silent failures before you need the backup.
If you’re setting up NFS storage for the first time, make sure you’ve got the export options right. I wrote about Proxmox Cluster NFS: Frontend Connects, Backend Fails which covers a similar issue where the mount looks fine but isn’t.
