On Fri, Jan 13, 2017 at 06:57:53PM +0100, Gianni Costanzi wrote: > Hi, > I'm new here and I've started using QEMU when I've started playing > with Unetlab/EVE Network simulator. > > I have some questions about compression and images with a compressed > backing file:
I think there's some misunderstanding here about compressed images in QEMU. I'll try to clarify: * You create a compressed image with 'qemu-img convert -c'. That is a copy of the original image with all the clusters compressed. * The compression is read-only: QEMU will read the compressed clusters, but everything that it writes will be uncompressed (also if you rewrite compressed clusters). * Therefore, there's no such thing as an image with compression enabled. In QEMU you don't compress an image, you compress individual clusters of data. An image can have a mix of compressed and uncompressed clusters. Berto
