USB external disk in 2-node Proxmox cluster – best way to use it for backups?

[Kratus]

Hi everyone,

I’m dealing with a backup design issue in my Proxmox setup and could use some advice.

I have a 2-node cluster with a QDevice:

• Alpha – 10.250.100.2/30
• Bravo – 10.250.100.6/30

The nodes are in different cities (different sites). The cluster itself works fine (HA, replication, QDevice quorum).

I recently bought an external USB disk and connected it to Bravo.
My initial idea was:

1. Create a VM running Proxmox Backup Server (PBS) on Bravo.
2. Pass the USB disk directly to the PBS VM.
3. Use this PBS to back up all VMs from both Alpha and Bravo.

The problem is the network layout.

Each node has two NICs:

• ens1f0np0 → vmbr0 (external/public traffic)
• ens1f1np1 → vmbr1 (internal cluster network: 10.250.100.x/30)

I tried creating a VLAN interface on Bravo (vmbr1.550) and using that for the PBS VM, but the VM cannot communicate even though the switch port is configured as a trunk. The VLAN just doesn’t reach the VM.

I also considered exporting the USB disk over NFS/CIFS so both nodes could use it, but that looked even less reliable, especially with a USB device.


What I'm trying to find out

Is there a proper or recommended way to use this USB disk (connected only to Bravo) as a backup target for VMs running on both Alpha and Bravo?


I’m open to:

• using PBS (preferred), or
• not using PBS if there’s a more suitable approach,
• any storage layout that makes sense for a 2-node cluster with a remote site.

Any suggestions or guidance would be greatly appreciated.


Thanks !