Stages of Live Migration(Virtualization)
To know the basics concepts of virtualization click here
Live Migration Process:
One of the major benefits of the OS virtualization is live Guest OS Migration. It has eliminated all the difficulties faced by process-level migration by moving the whole virtual machine while running the operating system. You can also perform multiple simultaneous live migrations to enable you to move many virtual machines quickly. These changes allow you to implement high levels of mobility and flexibility in private cloud solutions.
Stages of Live Migration :
Stage 1:
Pre-Migration stage: A target host will be preselected where the resources required to receive migration will be guaranteed.
Stage 2:
Repetitive Pre-Copy: During the first iteration, all memory pages are transferred from Host-A to Host-B. Subsequent iteration copy are only those pages dirtied during the previous transfer.
Stage 3:
Stop (suspend)-and-Copy: Here, VM will be suspended on Host-A and redirect its network traffic to Host-B. CPU state and any remaining inconsistent memory pages are then transferred like a final sync. This process will reach a consistent suspended copy of the VM at both Host-A and Host-B. Host-A will remain primary and it will be resumed in case of failure at this stage.
Stage 4:
Commitment to the hosts: Host-B sends the signal to Host-A that it has successfully received a consistent VM OS image. Host-A acknowledges the signal and destroys the VM. Host-B becomes the primary host for migrated VM.
Stage 5:
Activation of VM: The migrated VM on Host-B is now activated. Post-migration code connects to the local resources and resumes the operation.
