I'm trying to reduce the usage of a qcow2 image. I did the following:
qemu-img convert -p -f qcow2 -O qcow2 my_img.qcow2.backup my_img.qcow2
I outputs 200192 bytes and progress is stuck at 0.00%. CPU usage is pegged at 100% and I let it go for 2 hours. The input image file is 160G. Also, iotop says that there's no disk usage. What could qemu-img possibly be doing that's wasting this much time?
Also, I should mention, I've tried using raw output format and it does the same thing.
Best Answer
I had the very same probem with a 149G (virtual 168G) QCOW2 file. The conversion took two days while being stuck at 0.00% for the first day. It was just being very slow.
Subsequent conversions with zero fragmentation was as fast as can be expected. Try
-o preallocation=metadata
for improved performance.