[Libguestfs] virt-sparsify and iSCSI

Hi! This question emerged during testing of oVirt sparsify integration. oVirt now is able to run virt-sparsify on VM disks. But virt-sparsify seems to have no effect on iSCSI disks. Does virt-sparsify work on iSCSI disks? Maybe in sum situation, with some configuration of iSCSI server, with some specific virt-sparsify options? Shmuel