[libvirt-users] vol-wipe and delete

Hello all, I know libvirt has the following two commands: vol-wipe vol-delete Can someone please explain to me how these function? Do these only remove previous session data so that a new virtual instance cannot see it or does it remove it at the physical level level too so that the data cannot be found anywhere on the physical drive? I know Eucalyptus and KVM use sparse files upon instance creation and the instance thinks the ephemeral space is all zeroes even though it is just sparse. I appreciate any insight in how the two virsh commands work and if they use zeroes, sparse, or some other method. Thanks, Shawn