Solution for: Proxmox backup error due to iothread=1

If you see the following error when trying to backup a KVM VM image on Proxmox:

ERROR: Backup of VM 100 failed – disk ‘scsi0’ ‘zfsvols:vm-100-disk-1’ (iothread=on) can’t use backup feature currently. Please set backup=no for this drive at /usr/share/perl5/PVE/VZDump/ line 77. INFO: Backup job finished with errors TASK ERROR: job errors

edit /etc/pve/qemu-server/100.conf, look for a line similar to

scsi0: zfsvols:vm-100-disk-1,iothread=1,size=70G

and change it to

scsi0: zfsvols:vm-100-disk-1,iothread=0,size=70G

Afterwards, it’s possible to backup the VM.

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