Migration or Reinstantiation
BtrPlace supports two relocation methods for a VM. This page describes how these methods are supported.
Using a migration, a VM is moved from one node to another one. Hypervisors usually support cold and live migration. The following figure depicts the migration process. During a migration, the VM is running on its original node but resources are also booked on the destination node. The VM state and associated data are then copied on the destination node. Once the migration process terminated, resources on the source node are liberated and the VM is set running on the destination node.
Contrary to the migration, the re-instantiation does not copy the VM. A new VM having the same characteristics is forged then booted on the destination node. Once booted, the VM on the source node is shutdown. The action duration is currently considered as the sum of the forge action, the boot and the shutdown action. The following figure depicts a relocation process. This method is not suitable for a VM that have a particular state and identity, such as a desktop VM. It is however useful for a VM hosting a service replica. The tutorial Customizing a Model explains how to allow re-instantiation for a VM.
