virt-sparsify or other method to shrink virtual machines for backup?

Hi

I am trying to reduce the size of my qemu/kvm virtual machine backups.

Was wonder if I should use virt-sparsify to reduce the size of my vm backups?

For example I have VM_One.qcow2

qemu-img info VM_One.qcow2

image: VM_One.qcow2
file format: qcow2
virtual size: 100G (107374182400 bytes)
disk size: 77G
cluster_size: 65536
Format specific information:
compat: 1.1
lazy refcounts: true
refcount bits: 16
corrupt: false


from within VM_One df -h

Filesystem Size Used Avail Use% Mounted on
udev 2.9G 0 2.9G 0% /dev
tmpfs 597M 732K 596M 1% /run
/dev/mapper/vm_one--vg-root 95G 12G 79G 13% /
tmpfs 3.0G 0 3.0G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.0G 0 3.0G 0% /sys/fs/cgroup
tmpfs 3.0G 0 3.0G 0% /run/shm


Would virt-sparsify shrink VM_One.qcow2 from ~77G to around ~12G?

If so would the new image VM_One_sparsified.qcow2 if put back into production live would it then continue to grow as normal or is it now stuck to the shrunk size?

Can virt-sparsify be used on a backup image for example ( virt-sparsify VM_One_Backup.qcow2 VM_One_sparsified.qcow2 ) rather than the live / in service virtual machine VM_One.qcow2 ?

Thanks.