qemu-img convert -O qcow2 -c windows-7-best.qcow2 windows-7-best-compacted.qcow2 The -c flag compresses the image, often recovering 40% of your disk space. What does "best" actually look like? Let’s compare:
| Configuration | Boot Time | Sequential Read | Snapshot Time | Disk Space (Fresh Install) | | --- | --- | --- | --- | --- | | Raw IDE | 48 seconds | 120 MB/s | N/A | 18 GB | | QCOW2 (Defaults) | 34 seconds | 340 MB/s | 0.3 sec | 9 GB | | | 19 seconds | 890 MB/s | 0.1 sec | 7 GB | windows 7qcow2 best
qemu-img create -f qcow2 windows-7-best.qcow2 80G Note: The -f qcow2 flag ensures the correct format. Do not just use default parameters. Here is the optimized command to launch your Windows 7 installer: qemu-img convert -O qcow2 -c windows-7-best