I apologise if this is not the place to ask, but this question was actually bugging me for a long time now.
Is there any particular reason fast-diff was disabled for backup images in the first place? Like, any actual technical limitation, i.e. "don't enable it or it will break your backups"?
Or is it only because earlier versions of CEPH did not support fast-diff, so it was disabled for compatibility reasons?

ср, 13 янв. 2021 г. в 16:40, Brian Rosmaita <rosmaita.fossdev@gmail.com>:
On 1/13/21 4:37 AM, Christian Rohmann wrote:
> Hey everyone,
>
> I wrote a tiny patch to add the Ceph RDB feature of fast-diff to backups
> created by cinder-backup:
>
>   * https://review.opendev.org/c/openstack/cinder/+/766856/
>
>
> Could someone please take a peek and let me know of this is sufficient
> to be merged?

Thanks for raising awareness of your patch.  Right now, the cinder team
is prioritizing new driver reviews in light of the impending merge
deadline at wallaby milestone-2 next week:

http://lists.openstack.org/pipermail/openstack-discuss/2021-January/019720.html

So there may be a slight delay to your patch being reviewed.  If you
have some time, you can always help things along by reviewing some small
patches by other authors.

cheers,
brian

>
>
>
> Thanks and with kind regards,
>
>
> Christian
>
>
>