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On 07/10/15 13:36, Ed Leafe wrote:
> Several months ago I proposed an experiment [0] to see if switching the data model for the Nova scheduler to use Cassandra as the backend would be a significant improvement as opposed to the current design using multiple copies of the same data (compute_node in MySQL DB, HostState in memory in the scheduler, ResourceTracker in memory in the compute node) and trying to keep them all in sync via passing messages.

It seems to me (disclaimer: not a Nova dev) that which database to use 
is completely irrelevant to your proposal, which is really about moving 
the scheduling from a distributed collection of Python processes with 
ad-hoc (or sometimes completely missing) synchronisation into the 
database to take advantage of its well-defined semantics. But you've 
framed it in such a way as to guarantee that this never gets discussed, 
because everyone will be too busy arguing about whether or not Cassandra 
is better than Galera.

cheers,
Zane.