Hmm why wasn't I in to/cc list, was that intentional? On 10/17/19 5:26 AM, Christophe de Dinechin wrote: > > Cole Robinson writes: > >> This series is the first steps to teaching libvirt about qcow2 >> data_file support, aka external data files or qcow2 external metadata. >> >> A bit about the feature: it was added in qemu 4.0. It essentially >> creates a two part image file: a qcow2 layer that just tracks the >> image metadata, and a separate data file which is stores the VM > > s/is stores/stores/ Indeed, but what's the benefit of correcting grammar in a cover letter for already applied patches? > >> disk contents. AFAICT the driving use case is to keep a fully coherent >> raw disk image on disk, and only use qcow2 as an intermediate metadata >> layer when necessary, for things like incremental backup support. >> >> The original qemu patch posting is here: >> https://lists.gnu.org/archive/html/qemu-devel/2019-02/msg07496.html >> >> For testing, you can create a new qcow2+raw data_file image from an >> existing image, like: >> >> qemu-img convert -O qcow2 \ >> -o data_file=NEW.raw,data_file_raw=yes >> EXISTING.raw NEW.qcow2 > > What happens if you try to do that in place, i.e. EXISTING==NEW? > Results in an unbootable image in my testing. I'm guessing it initializes the raw image first, similar to trying to use 'qemu-img create' with an existing raw image as data_file https://bugzilla.redhat.com/show_bug.cgi?id=1688814#c8 - Cole -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
