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/QemuServer.pm 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.