In the YAML configuration of the imported VM with multiple disks, there is no bootOrder property configured for any disk. The bootable flag is put on the first disk by default, and the VM will boot from the first disk. If the first disk is not the actual bootable disk, VM will fail to boot because of no bootable device error, and it won't try to boot from the second disk. Users have to change the boot order and restart the VM.

Migration process should guarantee the imported VM could boot from correct disk. It should configure bootOrder on the correct disk, or make the bootable disk to be the first disk, so that the VM could boot from it by default.