Proxmox VE 9 vm backup with Veeam Backup & Replication 12.3.2

A

AndreasS

New Member
Sep 18, 2025
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Aachen, Germany
Good afternoon,

just a quick one regarding backing up virtual machines with Veeam Backup & Replication 12.3.2.

When backing up the vm veeam returns the following job log:

Additional Details: 18.09.2025 15:21:52 :: Job started at 9/18/2025 3:21:52 PM
18.09.2025 15:21:54 :: All objects have been queued for processing
18.09.2025 15:21:54 :: VMs size: 125 GB
18.09.2025 15:22:05 :: The worker VeeamWorkerFOO was prepared successfully
18.09.2025 15:23:34 :: VM-Name : Use worker VeeamWorkerFOO
18.09.2025 15:23:34 :: VM-NAme : Failed to perform backup: Failed to map disks
18.09.2025 15:24:16 :: Backing up the VM in the "HotAdd" mode
18.09.2025 15:24:22 :: The worker VeeamWorkerFOO was shut down successfully
18.09.2025 15:24:27 :: Job finished with error at 9/18/2025 3:24:27 PM

The 'Failed to map disks' according to Veeam paid enterprise support occurs because Proxmox VE 9 has introduced changes to the structure of block device details.

Here is their official workaround / solution until full support of VE9 in Veeam Backup & Replication 12.3.2:

I believe the error "Failed to perform backup: Failed to map disks" is occurring because Proxmox VE 9 has introduced changes to the structure of block device details. These changes are not yet supported by Veeam Backup for Proxmox v1.3 or earlier, which leads to the failure when Veeam attempts to map the disks during backup.

To resolve this issue, please consider the following options:
  1. Downgrade Proxmox VE:
    Downgrade your Proxmox VE host to a supported version, specifically Proxmox VE 8.2–8.4, as these versions are currently compatible with Veeam Backup for Proxmox.

  2. Workaround for Individual VMs:
    If downgrading is not feasible, you can configure the affected virtual machine to use the older, compatible machine structure:
    • In the Proxmox VE web console, locate the VM.
    • Navigate to Hardware → Machine → Edit → Advanced → Version.
    • Set the version to 8.2.
    • Reboot the VM for the change to take effect.
Please note that this workaround should be reverted manually once full support for Proxmox VE 9 is added to Veeam Backup for Proxmox.

Stay Updated:
For the latest updates regarding support for Proxmox VE 9, please refer to the following forum thread:
https://forums.veeam.com/post550872.html
Click to expand...

I hope that helps,

Take care,
Andreas
 
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Good morning all,

Proxmox VE 9 is now officially supported on most recent Veeam with Proxmox VE plugin according to this KB article:

Veeam KB4775 - Proxmox VE 9 plugin

  • I have tried backup with latest VM version, which is working now.
  • Download of single files (Copy To...) from backup is also working.
  • Restore of entire VM to original location is working (you need to disable or remove HA from the VM first!)
  • Restore of single file to orignal location (overwrite or keep) both not confirmed working, but this might be on my end.
Take care,
Andreas
 
Quick update, this is still under investigation of Veeam support. With latest Veeam version an most recent Proxmox-plugin it tries to use a Microsoft Hyper-V-helper instead of using Linux-helper/worker (we are backing up Hyper-V-Cluster as well as Proxmox-HA-Cluster).
 
Hello
I confirm that i had the same problem while restoring a Veeam agent backup : failed to prepare disk for restore.
With the update of the Proxmox Plugin, it works now.

Thanks !
 
Hello @jnthans,

glad the plugin update worked for you.

Regarding the incorrect Hyper-V helper issue that @AndreasS mentioned: This usually points to the Backup Proxy configuration. It's worth checking which proxy is set for the Proxmox environment and ensuring a Linux proxy is available and prioritized for this task, not the Windows one that handles your Hyper-V cluster.
 
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Hello @Bu66as,

I have created 4 Veeam Workers Type Proxmox VE, one for each node (qdevice is present, no worries).

Can you please advice where I can prioritize those for Proxmox task? Do I manually have to select one via entering the IP here:

Restore -> Guest File Restore -> Helper Host -> Linux Server:

a) ... (original host)? (not working)
b) Specify a different host? (if yes, I cannot specify the helper here, because they are not started yet, manual start of worker vm seems undesired?)
c) Use a temporary helper appliance? -> Which is so far starting one Windows VM on Hyper-V-Cluster.

1759848622083.png

1759848647777.png

I have been thinking of recreating the 4 helper maschines because they have been created before most recent proxmox veeam plugin has been installed on the backup server?

Regards,
Andreas
 
Last edited:
This isn't configured in the restore wizard itself, but on the backup repository. You don't need to recreate the workers.

The server that mounts the backup for a file-level restore (the Gateway Server) determines which virtualization platform it can use for the helper appliance. Your repository is currently using a Windows server as its gateway, which is why it's trying to deploy the helper on your Hyper-V cluster.

To fix this, go to Backup Infrastructure -> Backup Repositories. Right-click the repository where your Proxmox backups are stored and choose "Properties". Go to the "Repository" or "Gateway Server" settings tab. Change the "Gateway server" from "Automatic selection" to one of your Linux servers that is also a Proxmox backup proxy.

After changing this, Veeam will use that Linux server to perform the mount and will correctly start the helper appliance on one of your Proxmox nodes.
 
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Thanks a lot for pointing me in the right direction, so far I have been backing up to the existing (windows) backup repository. From your post I guess this is not working very well for file level restore if recommended at all.

It looks like I have to create one/several dedicated linux backup repositories under Veeam? (Which would be a pain in the arm as I have to possibly buy tons of backup storage).
 
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