VM Fails to backup and job gets stuck

[brokebit]

Hey folks,

I have a strange problem. I have one VM in my cluster that just won't backup. No issues backing up other VMs. This is on a three node 9.1.6 cluster that is current on all updates. The VM is a linux machine with a 256GB root disk. QCOW2 format. VMs are stored on an NFS mount from a Unifi UNAS. Backups go to another NFS mount on another UNAS machine.

The backup status gets to this point and then just hangs indefinitely and there is no traffic to/from the UNAS boxes:

INFO: starting new backup job: vzdump 119 --storage local --compress zstd --notification-mode notification-system --remove 0 --mode snapshot --notes-template '{{guestname}}' --node neutron
INFO: Starting Backup of VM 119 (qemu)
INFO: Backup started at 2026-04-04 13:20:56
INFO: status = running
INFO: VM Name: newkali
INFO: include disk 'scsi0' 'unas-pro8-proxmox:119/vm-119-disk-0.qcow2' 256G
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: creating vzdump archive '/var/lib/vz/dump/vzdump-qemu-119-2026_04_04-13_20_56.vma.zst'
INFO: started backup task 'f0aec091-1e38-4f2e-b57f-48c0f01fb156'
INFO: resuming VM again
INFO: 0% (0.0 B of 256.0 GiB) in 3s, read: 0 B/s, write: 0 B/s

Any ideas?

 

[brokebit]

Here is the VM Config:

root@neutron:/var/log/pve/tasks# qm config 119
boot: order=scsi0;net0
cores: 12
cpu: x86-64-v2-AES
lock: backup
memory: 30518
meta: creation-qemu=10.1.2,ctime=1774718981
name: newbox
net0: virtio=BC:24:11:0F:ED:23,bridge=vmbr0,firewall=1,queues=8
numa: 1
ostype: l26
scsi0: unas-pro8-proxmox:119/vm-119-disk-0.qcow2,aio=native,iothread=1,size=256G
scsihw: virtio-scsi-single
smbios1: uuid=2e0d66e2-6e54-45af-9184-5a0336358541
sockets: 1
vmgenid: 4dde0ca6-5f68-4753-b4da-040bbb512bca