You can migrate VMs between Computes Nodes managed by single Openstack Controller.
For Fail over or redundancy:
When you want to offer users different regions to provide legal considerations for data storage, redundancy across earthquake fault lines, or for low-latency API calls, you segregate your cloud. Use one of the following OpenStack methods to segregate your cloud: cells, regions, zones, and host aggregates.
Each method provides different functionality, and can be best divided into two groups:
Cells and regions, which segregate an entire cloud and result in running separate Compute deployments.
Availability zones and host aggregates, which merely divide a single Compute deployment.
You may refer to this link
Thanks,
Shankar.
can you give more details of how the instances are deployed, any shared volumes or your using swift? what kind of data?
No instances are deployed yet. Looking at portability between openstack providers and internal openstack deployments.
are you planning to move data from public openstack offerings to your own private setup? are they files, database dumps or what data your app generates?
I am planning on moving whole instances between stacks - I do not wish to go into the app data...rather to move all instances, db, sdn's, etc between stacks intact - for failover purposes between data centers.
What do you mean by instance here, whether VM or Openstack node?