Open Stack

Excerpts from Alex Leonhardt's message of 2014-06-18 13:51:41 -0700:
> hi guys,
> 
> am looking for some resource which parts of the system are required to be
> HA - I naturally would do  :
> 
> - DB
> - Rabbit
> - Controller node/s
> 
> we dont use glance and swift too much and wont really as I'd use it as a
> private / internal cloud - what other services would you consider needing
> HA and if so, is it possible to run Active/Active with the DB and Rabbit at
> least ?
> 

Active/Active DB would need to be done using a sync replication system
like MySQL cluster or Galera. These both recommend more than 2 nodes.
Also there are likely issues with the way OpenStack handles conflicting
commits to the database, so Active/Active may not even be possible
without a lot of testing.

RabbitMQ can be run in Active/Active w/ mirrored queues.

Both of the above would require some kind of STONITH mechanism to be
sure that split-brain doesn't corrupt your data.

All of the OpenStack controller services should be O-K except two that
I know of:

* Ceilometer's collector must be Active/Passive
* Neutron L3 agent needs to be Active/Passive unless patches have landed
  to change that