Open Stack

On 13:42 Aug 11, Brian Rosmaita wrote:
> On 8/7/15, 1:07 PM, "Jay Pipes" <jaypipes at gmail.com> wrote:
> 
> >So, here's the crux of the issue. Nova and Cinder **do not want to speak
> >the Glance REST API** to either upload or download image bits from
> >storage. Streaming image bits through the Glance API endpoint is a
> >needless and inefficient step, and Nova and Cinder would like to
> >communicate directly with the backend storage systems.
> 
> Exactly why do you want to communicate directly with the backend storage
> systems?  Streaming image bits through Glance appears to be "needless and
> inefficient", but if an end-user is booting 1K instances from some custom
> image, Glance's image cache makes an enormous difference in delivery time.
> 
> So I'm curious about what exactly the use cases for direct backend storage
> communication are, and why Glance can't meet them.

I don't think you read my email carefully in this discussion...

Streaming bits to Glance with cache or not will *never* outperform a block
storage backend that can do a copy on write of an image when that storage
backend is also the glance backend store.  While Glance is copying the bits,
the block storage backend is able to create a reference pointer of that image,
to the new volume and move on. No copying necessary.

-- 
Mike Perez