[openstack-dev] [Nova] Does Nova really need an SQL database?

Chris Friesen chris.friesen at windriver.com
Wed Nov 20 16:22:01 UTC 2013

On 11/20/2013 10:06 AM, Soren Hansen wrote:
> 2013/11/18 Mike Spreitzer <mspreitz at us.ibm.com>:
>> There were some concerns expressed at the summit about scheduler
>> scalability in Nova, and a little recollection of Boris' proposal to
>> keep the needed state in memory.
>> I also heard one guy say that he thinks Nova does not really need a
>> general SQL database, that a NOSQL database with a bit of
>> denormalization and/or client-maintained secondary indices could
>> suffice.
> I may have said something along those lines. Just to clarify -- since
> you started this post by talking about scheduler scalability -- the main
> motivation for using a non-SQL backend isn't scheduler scalability, it's
> availability and resilience. I just don't accept the failure modes that
> MySQL (and derivatives such as Galera) impose.
>> Has that sort of thing been considered before?
> It's been talked about on and off since... well, probably since we
> started this project.
>> What is the community's level of interest in exploring that?
> The session on adding a backend using a non-SQL datastore was pretty
> well attended.

What about a hybrid solution?

There is data that is only used by the scheduler--for performance 
reasons maybe it would make sense to store that information in RAM as 
described at


For the rest of the data, perhaps it could be persisted using some 
alternate backend.


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