Open Stack

I was wondering if there is any interest in adding an 
"on_shared_storage" field to the Instance class.  This would be set once 
at instance creation time and we would then be able to avoid having the 
admin manually pass it in for the various API calls 
(evacuate/rebuild_instance/migration/etc.)

It could even be set automatically for the case of booting off block 
storage, and maybe we add a config flag indicating that a given compute 
node is using shared storage for its instances.

This would also allow for "nova host-evacuate" to work properly if some 
of the instances are on unshared storage and some are booting from block 
storage (which is shared).  As it stands, the host-evacuate command 
assumes that they're all the same.

Thoughts?

Chris