Once the installation is complete, the QCOW2 file will begin to swell. Windows 8.1 is chatty; it writes logs, indices, and telemetry data constantly. This constant writing (write amplification) can degrade the performance of QCOW2 over time.

Issue: The "Black Screen of Death" on Boot.

Issue: QCOW2 File Corruption.

Windows 8.1 doesn't include VirtIO block drivers natively. Download the latest stable VirtIO ISO from Fedora’s repository:

wget https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/virtio-win.iso

Inside the guest:

On the host (image maintenance):

qemu-img check -r all win81.qcow2
qemu-img convert -O qcow2 -c win81.qcow2 win81_compressed.qcow2  # compress

qemu-img create -f qcow2 windows81.qcow2 40G

The challenge: Windows setup cannot see the QCOW2 disk if it expects IDE/SATA but we use virtio-block. The workaround:

Better approach – Load drivers during Windows Setup:

qemu-system-x86_64 \
  -enable-kvm \
  -cpu host \
  -smp 4 \
  -m 4096 \
  -drive file=win81.qcow2,if=none,id=drive0 \
  -device virtio-blk-pci,drive=drive0 \
  -cdrom win8.1.iso \
  -cdrom virtio-win.iso \
  -boot d \
  -vga qxl \
  -machine type=q35,accel=kvm \
  -usb -device usb-tablet

When Windows Setup starts, at the "Where do you want to install Windows?" screen:

Summary

Setup & prerequisites

Installation methods (overview)

Pros

Cons / Risks

Step-by-step (practical, command-line example) Assumptions: you have Windows_8.1_Pro.iso and want a 40 GB qcow2 named win8.1.qcow2.

qemu-img create -f qcow2 win8.1.qcow2 40G

qemu-system-x86_64 -m 8192 -smp 2 -boot d \
  -drive file=win8.1.qcow2,if=virtio,cache=none \
  -cdrom Windows_8.1_Pro.iso \
  -device virtio-net-pci,netdev=net0 -netdev user,id=net0 \
  -enable-kvm -vga qxl

Performance & tuning tips

Security & licensing

Verdict

Related search suggestions (If you want, I can provide search terms for downloads, virtio drivers, or step-by-step guides.)

Here’s a solid, structured review of installing Windows 8.1 as a QEMU QCOW2 virtual machine. It covers performance, setup steps, driver considerations, and overall suitability.

Use virt-install for a headless or scriptable installation:

virt-install \
  --name win81 \
  --ram 4096 \
  --vcpus 2 \
  --disk path=windows81.qcow2,format=qcow2 \
  --cdrom /path/to/Windows_8.1.iso \
  --disk path=virtio-win.iso,device=cdrom \
  --os-variant win8.1 \
  --graphics spice \
  --network network=default,model=virtio

Important: When Windows setup starts and asks for a drive, you won't see any disk. Click Load Driver → Browse to the VirtIO CD drive → viostor\w8.1\amd64 → Next. The disk will appear. Proceed with normal installation.