Obsolete:TheBetterPathToLiveMigrationResizing
Contents
The Better Path To Live Migration and Resizing
Rationale
The current code path for resizing and live migration is what you could call hairy in that the state-machine that is used to accomplish these 2 types of tasks (which are by there very nature extremely similar) is itself complex and could benefit from rework around a more organized state-machine which would be orchestrated by an external entity, of which said external entity can handle the intricacies of cross-compute communication as well as state-machine transitions and associated failure scenarios. This will make said operation more reliable and centralize the orchestration of said operations to a single entity, which instead of having multiple functions, one or 2 may suffice. Therefore the complexity of code reviews and understanding the complexity of said operations becomes lower and makes them easier to [test, modify, understand].
Definitions
- Live migration
- Moving a instance (and associated) resources from one compute node to another compute node while the instance is still running.
- Resizing
- Moving a powered-off instance (and associated) resources from one compute node to another compute node which can support the instance with re-sized capabilities (more/less VCPU for example).
Current path
Live migrate simple
Live migrate (volume backed)
