Open Stack

On Fri, Mar 16, 2018 at 09:23:11AM -0700, melanie witt wrote:
> On Fri, 16 Mar 2018 17:33:30 +0200, Peter Penchev wrote:
> > Would there be any major opposition to adding a StorPool shared
> > storage image backend, so that our customers are not limited to
> > volume-backed instances?  Right now, creating a StorPool volume and
> > snapshot from a Glance image and then booting instances from that
> > snapshot works great, but in some cases, including some provisioning
> > and accounting systems on top of OpenStack, it would be preferable to
> > go the Nova way and let the hypervisor think that it has a local(ish)
> > image to work with, even though it's on shared storage anyway.
> 
> Can you be more specific about what is limiting you when you use
> volume-backed instances?

It's not a problem for our current customers, but we had an OpenStack
PoC last year for a customer who was using some proprietary
provisioning+accounting system on top of OpenStack (sorry, I really
can't remember the name).  That particular system simply couldn't be
bothered to create a volume-backed instance, so we "helped" by doing
an insane hack: writing an almost-pass-through Compute API that would
intercept the boot request and DTRT behind the scenes (send a modified
request to the real Compute API), and then also writing
an almost-pass-through Identity API that would intercept the requests to
get the Compute API's endpoint and slip our API's address there.
The customer ended up not using OpenStack for completely unrelated
reasons, but there was certainly at least one instance of this.

> We've been kicking around the idea of beefing up
> support of boot-from-volume in nova such that "automatic boot-from-volume
> for instance create" works well enough that we could consider
> boot-from-volume the first-class way to support the vast variety of cinder
> storage backends and let cinder handle the details instead of trying to
> re-implement support of various storage backends in nova on a selective
> basis. I'd like to better understand what is lacking for you when you use
> boot-from-volume to leverage StorPool and determine whether it's something
> we could address in nova.

I'll see if I can remember anything more (ISTR also another case of
something that couldn't boot a volume-backed instance, but I really
cannot remember even what it was).  The problem was certainly not with
OpenStack proper, but with other systems built on top of it.

Best regards,
Peter