Windows 7 Qcow2 !!top!! -

You can create instantaneous virtual machine snapshots. The hypervisor freezes the base image and writes new data to a separate layer, allowing for seamless rollbacks.

Windows 7 does not support VirtIO-FS for shared folders in a stable manner. For file sharing, SMB/Samba is the more robust and reliable solution. Windows 7 Qcow2