Re: Clarification regarding new qemu-img convert --target-is-zero flag

[Eric Blake]

On 6/10/20 10:42 AM, David Edmondson wrote:
> On Wednesday, 2020-06-10 at 18:29:33 +03, Sam Eiderman wrote:
>
> > Excuse me,
> >
> > Vladimir already pointed out in the first comment that it will skip
> > writing real zeroes later.
>
> Right. That's why you want something like "--no-need-to-zero-initialise"
> (the name keeps getting longer!), which would still write zeroes to the
> blocks that should contain zeroes, as opposed to writing zeroes to
> prepare the device.

Or maybe something like:

qemu-img convert --skip-unallocated

which says that a pre-zeroing pass may be attempted, but it if fails, 
only the explicit zeroes need to be written rather than zeroes for all 
unallocated areas in the source (so the resulting image will NOT be an 
identical copy if there were any unallocated areas, but that the user is 
okay with that).

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org