[openstack-dev] [nova][scheduler] Updating Our Concept of Resources

Ed Leafe ed at leafe.com
Mon Jun 1 12:40:17 UTC 2015

Several of the discussions at Vancouver got me thinking about what seems to me to be a fundamental mis-match in Nova: the way we think about resources, and how we handle requesting/claiming them. I wrote down my initial thoughts (http://blog.leafe.com/rethinking-resources/), but as many of you took the week off after the summit, I waited until today to start a ML discussion.

Nova started when "the cloud" was pretty much the VPS model of on-demand compute: you had big powerful servers that you wanted to virtualize into several smaller chunks, and you did that with hypervisors on those servers. Along with this came the concept of "flavors", which were the available portions of the overall server you could request.

Over the years, though, that model has become just one of many (bare metal, NUMA, etc.), yet our internal model still tries to force everything into the flavor world. And with the advent of technologies such as LXD, it seems likely that the VPS model will begin to fade away and replaced by more efficient ways to share compute.

We need to update our concept of a resource internally in Nova, both in the DB and in code, and stop thinking that every request should have a flavor. This is also the single biggest blocker in separating the Scheduler into a separate service that can be used to allocate resources in Cinder and Neutron, too, because we've tied it exclusively to the concept of a VPS resource. I'd like to start a discussion and get people's opinions on this. I have some ideas, of course, but I know that as these are not simple issues, getting input from many different perspectives is going to lead to a better approach. So: what do you think would be a better way to represent resources, as well as a better way to represent a request for some of those resources?

-- Ed Leafe

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