Open Stack

> 1) Continue to add fields to the instances table (or compute_nodes
> table) for these main attributes like cpu_arch, etc.
> 2) Use the custom key/value table (instance_metadata) to store these
> attribute names and their values
> 3) Do both 1) and 2)

I've no particular preference here, but if we start adding attributes to instance_metadata that nova code specifically knows about, we need to ensure there is a good way to tell the difference between "nova" metadata and "user" metadata. I do not believe key prefixes will provide this difference cleanly.

Currently, instance_metadata is for user-provided attributes only and nova is agnostic to their contents. In the api, they are presented as such, and there are quotas on the number of metadata items the user can set. This would all break if we start adding "nova" metadata without further api and db (small) changes.