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