[ovirt-users] Convert HDD to Thin

Hi Am using oVirt 3.5 , and mapped 1.5TB if LUN from Dell Unity have deployed 50 vms in that lun , when I check the allocated space in storage its showing 800GB in storage whereas in oVirt its showing 1.4TB in oVirt . Is there any way to shrink the same in oVirt ? Thanks, Nagaraju