What the meaning of Zero-Downtime Migration(also called Online Migration)
The Zero-Downtime Migration is the type of migration of a virtual environment between different physical machines when memory, storage, and network connectivity of the virtual environment are transferred and resumed on the destination node.
Zero-Downtime Migration includes the following stages:
Once you start the migration, Virtuozzo Server checks whether the destination server meets all migration requirements and the virtual machine or Container can be migrated to this server.
pre-copy memory migration, when snapshot created to track any changes in the migrating VE
The virtual machine or container on the source server is suspended
The remaining data will be copied to the destination, and the VE will be resumed on the destination host. The time between stopping the VE on the original host and resuming it on destination is called the outage time, and ranges from a few milliseconds to seconds in most cases.
With the virtual environment suspended, a minimal subset of the execution state (CPU state, registers and, optionally, non-pageable memory, etc.) is transferred to the target. The VM is then resumed at the target.