Definition - What does Live Migration mean?
Live migration is the process of transferring a live virtual machine from one physical host to another without disrupting its normal operation. Live migration enables the porting of virtual machines and is carried out in a systematic manner to ensure minimal operational downtime.
Techopedia explains Live Migration
Live migration is generally performed when the host physical computer/server needs maintenance, updating and/or to be switched between different hosts. To start off, the data in a virtual machine's memory is first transferred to the target physical machine. Once the memory copying process is complete, an operational resource state consisting of CPU, memory and storage is created on the destination machine. After that, the virtual machine is suspended on the original site and copied and initiated on the destination machine along with its installed applications. The whole process has a minimal downtime of seconds in between migration - specifically in copying memory content. However, that can be reduced by a few techniques such as pre-paging and the probability density function of memory.