On Thu, Apr 11, 2019 at 9:02 AM Stefano Garzarella <sgarz...@redhat.com> wrote: > > On Thu, Apr 11, 2019 at 08:35:44AM -0400, Jason Dillaman wrote: > > On Thu, Apr 11, 2019 at 7:00 AM Stefano Garzarella <sgarz...@redhat.com> > > wrote: > > > > > > RBD APIs don't allow us to write more than the size set with rbd_create() > > > or rbd_resize(). > > > In order to support growing images (eg. qcow2), we resize the image > > > before RW operations that exceed the current size. > > > > What's the use-case for storing qcow2 images within a RBD image? RBD > > images are already thinly provisioned, they support snapshots, they > > can form a parent/child linked image hierarchy. > > > > Hi Jason, > I understand your point of view, maybe one use case could be if you have > a qcow2 image and you want to put it in the rdb pool without convert it. > > I'm going through this BZ [1] and I'll ask if they have other > use cases in mind.
Assuming no good use-cases, perhaps it would just be better to make the qemu-img error messages more clear. > Anyway, if we want to support only raw format on RBD driver, maybe we > should return something different from current behaviour, also avoiding > to create the image: > > $ qemu-img create -f qcow2 rbd:test/qcow.img 1G > qemu-img: rbd:test/qcow.img: Could not write qcow2 header: Invalid argument > > What do you think? > > Thanks, > Stefano > > [1] https://bugzilla.redhat.com/show_bug.cgi?id=1171007 -- Jason
