Notes about Post-Copy Live Migration
Post-Copy steps
- suspends the migrating VM at the source node
- copies minimal processor state to the target node
- resumes the virtual machine
- begins fetching memory pages over the network from the source.
The manner in which pages are fetched gives rise to different variants
trade-off
- For VMs with read-intensive workloads, pre-copy would be the better approach
- For large-memory or write-intensive workloads, post-copy would better suited.
Pre-copy是为了能够尽量地减少downtime，并且不影响服务的运作;而post-copy则是为了减少total migration time且让程序能够持续的执行。