Description of problem: virt-sparsify takes 'indisk' and 'outdisk' parameters. This is a problem for multi-disk virtual machines, especially ones using LVM, MD, LDM or other volume management where a single filesystem might be spread over multiple disks. I have a 3 disk Windows VM using LDM that simply cannot be sparsified properly, because it's not possible to mount the LDM partitions that take up the majority of the disk space. Version-Release number of selected component (if applicable): libguestfs 1.21.0
I documented the problem upstream: https://github.com/libguestfs/libguestfs/commit/6f02e33c6fbf2f14ba11ef07cb078ad6f6b2fea3 (Note this is just documentation, NOT a fix)