Open Stack

On Aug 25, 2016, at 3:19 PM, Andrew Laski <andrew at lascii.com> wrote:

> One other thing to note is that while a flavor constrains how much local
> disk is used it does not constrain volume size at all. So a user can
> specify an ephemeral/swap disk <= to what the flavor provides but can
> have an arbitrary sized root disk if it's a remote volume.

This kind of goes to the heart of the argument against flavors being the sole source of truth for a request. As cloud evolves, we keep packing more and more stuff into a concept that was originally meant to only divide up resources that came bundled together (CPU, RAM, and local disk). This hasn’t been a good solution for years, and the sooner we start accepting that a request can be much more complex than a flavor can adequately express, the better.

If we have decided that remote volumes are a good thing (I don’t think there’s any argument there), then we should treat that part of the request as being as fundamental as a flavor. We need to make the scheduler smarter so that it doesn’t rely on flavor as being the only source of truth.

The first step to improving Nova is admitting we have a problem. :)


-- Ed Leafe