On Fri, Mar 14, 2025 at 03:34:46PM +0100, Peter Krempa wrote: > On Fri, Mar 14, 2025 at 14:18:03 -0000, Michael Niehren wrote: > > one more ... > > > > what would happen, if i create the qcow2 image with zstd compression enabled and > > use the '--reuse-external' flag ? > > Would qemu write compressed data in it or not ? > > It would not be compressed, as I've explained earlier (On technical > lists it's preferred if context from what you're replying to is not > trimmed so that it can be reffred back to) actual compression of blocks > needs to be requested explicitly. The qcow2 header setting merely states > which algorithm should be used if blocks are compressed. Also, AFAIK, qemu will not write compressed data during "normal" usage by a running VM. The compression only gets applied during full image conversion processes. iow, 'qemu-img convert' can be used to create a compressed image, from a non-compressed image. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
