How Live Migration works on Hyper-V

1.Live migration setup

• Source host  creates TCP connection with destination host
• VM configuration data is transferred to destination host
• A skeleton VM is setup at destination host
• Physical memory is allocated to that VM

2.Memory pages are transferred from the source to destination host

• In-state memory (working set) of the VM will be transferred first
• Default page size is 4 KB
• All utilized pages will be copied to destination
• Modified pages are tracked by source and marked as being modified
• Several iteration of copy process will take place

3.Remaining modified pages will be transferred to destination host

• VM is then registered and the device state is transferred
• Less modified pages implies fast migration
• Total working set is copied to destination

4.Move storage handle from source to destination

• Till this step VM at destination host is not online

5.Once control of storage is transferred, VM will be online and resumed at destination

• Now the VM is completely migrated and running on destination host

6.Network cleanup

• Message is sent to physical network switch causes it to relearn MAC address of migrated VM