Live migration is the movement of a virtual machine from one physical host to another while continuously powered-up. When properly carried out, this process takes place without any noticeable effect from the point of view of the end user. Live migration allows an administrator to take a virtual machine offline for maintenance or upgrading without subjecting the system's users to downtime.
One of the most significant advantages of live migration is the fact that it facilitates proactive maintenance. If an imminent failure is suspected, the potential problem can be resolved before disruption of service occurs. Live migration can also be used for load balancing, in which work is shared among computers in order to optimize the utilization of available CPU resources.