QCOW2

Installing Windows 8.1 into a (QEMU Copy-On-Write) disk image is a popular way to run the legacy OS in virtualization environments like KVM/QEMU , Proxmox , or GNOME Boxes .

  • Use raw storage underneath QCOW2? No, keep QCOW2 but add -o preallocation=metadata when creating.
  • Enable KSM (Kernel Same‑page Merging) if running multiple Windows VMs.
  • Set CPU governor to performance.

Check the converted image:

From a VMDK (VMware):

  • qcow2 supports internal snapshots (qemu-img snapshot). libvirt also supports external snapshots. For consistent backups, shut down guest or use Windows VSS-aware backup inside the VM.
  • External snapshots: create a qcow2 backing file for easier rollback. Example: 
    qemu-img create -f qcow2 -b /var/lib/libvirt/images/win8.1.qcow2 /var/lib/libvirt/images/win8.1-snap1.qcow2
  • Convert to raw for slightly better performance (at cost of space): qemu-img convert -O raw src.qcow2 dest.img.
  • Windows 8.1 ISO (Pro/Enterprise, x64 recommended for modern CPU)
  • qemu-img utility (part of QEMU)
  • VirtIO driver ISO (from Fedora or official GitHub repo)