Whilst using qm importdisk you might experience the following problem:
root@hv:~# qm importdisk 123 clients-disk.vmdk nas03 importing disk 'clients-disk.vmdk' to VM 123 ... iscsiadm: No session found. transferred 0.0 B of 40.0 GiB (0.00%) qemu-img: Could not open 'clients-disk.vmdk': invalid VMDK image descriptor copy failed: command '/usr/bin/qemu-img convert -p -n -f vmdk --target-image-opts clients-disk.vmdk 'file.driver=iscsi,file.transport=tcp,file.initiator-name=XXX,file.lun=12,driver=raw'' failed: exit code 1
The solution is used this command:
qemu-img info [source filename]
You may discover that although the filename ends with .vmdk, it’s actually a RAW file. So to convert it, do this:
qemu-img convert -f raw clients-disk.vmdk -O qcow2 clients-disk.vmdk