Re: Is rbd_discard enough to wipe an RBD image?

[Josh Durgin <jdurgin@redhat.com>]

On 12/21/2015 11:00 AM, Wido den Hollander wrote:
> My discard code now works, but I wanted to verify. If I understand Jason
> correctly it would be a matter of figuring out the 'order' of a image
> and call rbd_discard in a loop until you reach the end of the image.

You'd need to get the order via rbd_stat(), convert it to object size 
(i.e. (1 << order)), and fetch stripe_count with rbd_get_stripe_count().

Then do the discards in (object size * stripe_count) chunks. This
ensures you discard entire objects. This is the size you'd want to use
for import/export as well, ideally.

> I just want libvirt to be as feature complete as possible when it comes
> to RBD.

I see, makes sense.

Josh