Proxmox Backup failed on NFS Share


Jul 20, 2021
Hi guys

Unfortunately, I've been having a problem for some time and don't really know what to do next. It seems that the qcow2 disk is defective, a Windows Server 2012 R2 is running on this VM and is used as a domain controller.I don't dare upgrade the system because I don't know whether it will fail completely.

- Proxmox Backup to NFS Share fails. (ERROR: backup_complete_cb -5)
- Proxmox backup to local storage fails (ERROR: backup_complete_cb -5)
- Windows Backup also aborts (E/A Errors)
- Various backup software also crashes

RAID-Controller: Adaptec 6405E

Proxmox Version:
pve-manager: 3.0-17 (pve-manager/3.0/f8f25665)
running kernel: 2.6.32-20-pve
proxmox-ve-2.6.32: 3.0-100
pve-kernel-2.6.32-20-pve: 2.6.32-100
lvm2: 2.02.98-pve4
clvm: 2.02.98-pve4
corosync-pve: 1.4.7-1
openais-pve: 1.1.4-3
libqb0: 0.11.1-2
redhat-cluster-pve: 3.2.0-2
resource-agents-pve: 3.9.2-4
fence-agents-pve: 4.0.0-2
pve-cluster: 3.0-20
qemu-server: 3.0-12
pve-firmware: 1.1-6
libpve-common-perl: 3.0-27
libpve-access-control: 3.0-7
libpve-storage-perl: 3.0-6
vncterm: 1.1-8
vzctl: 4.0-1pve6
vzprocps: 2.0.11-2
vzquota: 3.1-2
pve-qemu-kvm: 1.4-12
ksm-control-daemon: 1.1-1

Any suggestion?

first of all I'd try make a copy to a different physical disk of the image file while the VM is down and check if everything is okay with the underlying physical disk (e.g. with smartctl if that even existed in your version) and check the system logs. If that already fails, you might want to try a tool like
After that you can use qemu-img check /path/to/copied-file.qcow2, which also has a repair option -r. If that also fails, your best bet might be to try and copy the data from within the guest to outside.

P.S. it's highly recommended to upgrade your system. Proxmox VE 3 hasn't been supported or receiving (security) updates for many years!
  • Like
Reactions: mare19
Hi Fiona

Thank you for the fast answer!

I think we will try to copy the data to a new VM outside and yes you are right with the VE Version. :)

Best regards,


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