Back up Proxmox virtual machines
Use vzdump or the backup server so each Proxmox guest has a copy outside the disk that holds its virtual disk.
A scheduled vzdump job can write a snapshot-mode or stop-mode archive to NFS, PBS, or another node. Snapshot mode needs a storage that supports snapshots. Stop mode is simpler and interrupts the guest, so reserve it for machines that can pause.
Keep the archive, the VMID, and the bridge name together. A restore with qmrestore or the Proxmox Backup Server UI should land on storage that is not the failed volume.
The sample below checks that a local archive exists and is non-empty before you trust the nightly job.
#!/usr/bin/env bash
set -euo pipefail
archive="/var/lib/vz/dump/backup-proxmox-vms.vma.zst"
test -s "$archive"
echo "Archive is present: $archive"