Re: [libvirt] [PATCH 00/30] storagefile, security: qcow2 data_file support
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