[libvirt] changing compat when create volume from volume via libvirt api

[Vasiliy Tolstov]

I'm use via php binding
https://libvirt.org/html/libvirt-libvirt-storage.html#virStorageVolCreateXMLFrom

and see that image grows:

image: new.qcow2
file format: qcow2
virtual size: 4.9G (5242880000 bytes)
disk size: 854M
cluster_size: 65536
Format specific information:
    compat: 0.10
    refcount bits: 16

image: old.qcow2
file format: qcow2
virtual size: 4.9G (5242880000 bytes)
disk size: 277M
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false

Why libvirt create new image with different compat?
-- 
Vasiliy Tolstov,
e-mail: v.tolstov at selfip.ru