I have numerous qcow2 images which need to be reduced in size and have their maximum size (virtual size) reduced.  Physical disk space became so low that VMs "auto-paused" themselves, I moved enough images to solve the immediate problem but need to rectify the underlying issue.  It seems that qcow[2] files are grown in size such that the data inside of them takes about 50-60% of the space (does anyone know the actual algorithm or how to control it?).  Given the total physical disk space on the hypervisors, I need something more restrictive.

Our hypervisors are a mix of Ubuntu 14 or 16 LTS (qemu-img 2.2 or 2.5).  After doing all the preparation (defragment, reduce OS partition size) "qemu-img resize" reports that shrinking isn't supported yet.  My web research indicates that, to accomplish this,  I have to:

convert to raw

shrink the image

convert back to qcow[2]

increase the image size to provide for some growth

I'm hoping I've missed something in my research and that someone knows an easier way.  I don't feel constrained to qemu-img but this is a production environment precluding consideration of experimental software.  Virt-resize, guestfish or any other reasonable option is fine with me.  Solutions or ideas?  Thanks.